Patent Publication Number: US-2023140303-A1

Title: Suprachoroidal injection device

Description:
BACKGROUND 
     The human eye comprises several layers. The white outer layer is the sclera, which surrounds the choroid layer. The region between the sclera and the choroid layer may be referred to as the suprachoroidal space, though the sclera and choroid layer may be in direct apposition with each other. The retina is interior to the choroid layer. The sclera contains collagen and elastic fiber, providing protection to the choroid and retina. The choroid layer includes vasculature providing oxygen and nourishment to the retina. The retina comprises light sensitive tissue, including rods and cones. The region between the choroid and the retina may be referred to as the subretinal space, though the choroid and the retina may be in direct apposition with each other. The vitreous humor is a gel-like tissue contained in the largest interior region of the eye (i.e., the vitreous chamber), interior to the retina. 
     In some scenarios, it may be desirable to dispense a therapeutic agent to a patient&#39;s eye to treat one or more ocular conditions. Such ocular conditions may include, by way of example only, macular degeneration, retinitis pigmentosa, diabetic retinopathy, and/or other ocular conditions. The dispensed therapeutic agent may comprise various kinds of drugs including but not limited to small molecules, large molecules, cells, and/or gene therapies, etc. As described in U.S. Pat. No. 10,226,379, entitled “Method and Apparatus for Subretinal Administration of Therapeutic Agent,” issued Mar. 12, 2019, the disclosure of which is incorporated by reference herein, in its entirety, a therapeutic agent may be administered to the subretinal space (i.e., the interstitial region between the choroid and the retina). Alternatively, a therapeutic agent may be administered to the suprachoroidal space (i.e., the interstitial region between the sclera and the choroid) or to the vitreous region of the eye. 
     While a variety of surgical methods and instruments have been made and used to treat an eye, it is believed that no one prior to the inventors has made or used the invention described in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the specification concludes with claims which particularly point out and distinctly claim this technology, it is believed this technology will be better understood from the following description of certain examples taken in conjunction with the accompanying drawings, in which like reference numerals identify the same elements and in which: 
         FIG.  1    depicts a perspective view of an example of an instrument for delivery of a therapeutic agent to a suprachoroidal space; 
         FIG.  2    depicts a perspective view of a head of the instrument of  FIG.  1   ; 
         FIG.  3    depicts another perspective view of the head of  FIG.  2   ; 
         FIG.  4    depicts a front elevation view of the head of  FIG.  2   ; 
         FIG.  5    depicts a side cross-sectional view of the head of  FIG.  2   , taken along 5-5 of  FIG.  4   ; 
         FIG.  6    depicts a side elevation view of the instrument of  FIG.  1   , with the head of  FIG.  2    engaged with a schematic representation of an eye of a patient; 
         FIG.  7    depicts a side cross-sectional view of the head of  FIG.  2    engaged with a schematic representation of an eye of a patient; 
         FIG.  8 A  depicts a side cross-sectional view of another example of a head that may be incorporated into the instrument of  FIG.  1   , with the head engaging a schematic representation of an eye of a patient, and with a needle in a retracted position; 
         FIG.  8 B  depicts a side-cross-sectional view of the head of  FIG.  8 A  engaging a schematic representation of an eye of a patient, and with the needle in an advanced position; 
         FIG.  9 A  depicts a side cross-sectional view of another example of a head that may be incorporated into the instrument of  FIG.  1   , with the head engaging a schematic representation of an eye of a patient, and with a needle in a retracted position; 
         FIG.  9 B  depicts a side-cross-sectional view of the head of  FIG.  9 A  engaging a schematic representation of an eye of a patient, and with the needle in an advanced position; 
         FIG.  10    depicts a side elevation view of another example of a head that may be incorporated into the instrument of  FIG.  1   , with a needle protruding distally from the head; 
         FIG.  11    depicts a side elevation view of the needle of  FIG.  10    disposed in a schematic representation of an eye of a patient, and with the needle in several alternative use positions; 
         FIG.  12    depicts a schematic view of another example of a head that may be incorporated into the instrument of  FIG.  1   ; 
         FIG.  13    depicts a plot of voltage as a function of needle depth associated with an example of use of the head of  FIG.  12   ; 
         FIG.  14    depicts a side elevation view of another example of a head that may be incorporated into the instrument of  FIG.  1   , with a needle of the head disposed in layers of an eye of a patient; 
         FIG.  15    depicts a side elevation view of another example of a head that may be incorporated into the instrument of  FIG.  1   , with a needle of the head disposed in layers of an eye of a patient; 
         FIG.  16    depicts a perspective view of another example of an instrument for delivery of a therapeutic agent to a suprachoroidal space; 
         FIG.  17    depicts a side cross-sectional view of a head of the instrument of  FIG.  16    engaged with a schematic representation of an eye of a patient; 
         FIG.  18 A  depicts a schematic view of a first stage of a procedure where the instrument of  FIG.  16    is used to deliver therapeutic agent to a suprachoroidal space; 
         FIG.  18 B  depicts a schematic view of a second stage of a procedure where the instrument of  FIG.  16    is used to deliver therapeutic agent to a suprachoroidal space; 
         FIG.  18 C  depicts a schematic view of a third stage of a procedure where the instrument of  FIG.  16    is used to deliver therapeutic agent to a suprachoroidal space; 
         FIG.  19    depicts a side cross-sectional view of the head of the instrument of  FIG.  16    engaged with a schematic representation of an eye of a patient, with a needle disposed in a thin sclera layer; and 
         FIG.  20    depicts a side cross-sectional view of the head of the instrument of  FIG.  16    engaged with a schematic representation of an eye of a patient, with a needle disposed in a thick sclera layer. 
     
    
    
     The drawings are not intended to be limiting in any way, and it is contemplated that various embodiments of the technology may be carried out in a variety of other ways, including those not necessarily depicted in the drawings. The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present technology, and together with the description serve to explain the principles of the technology; it being understood, however, that this technology is not limited to the precise arrangements shown. 
     DETAILED DESCRIPTION 
     The following description of certain examples of the technology should not be used to limit its scope. Other examples, features, aspects, embodiments, and advantages of the technology will become apparent to those skilled in the art from the following description, which is by way of illustration, one of the best modes contemplated for carrying out the technology. As will be realized, the technology described herein is capable of other different and obvious aspects, all without departing from the technology. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not restrictive. 
     It is further understood that any one or more of the teachings, expressions, embodiments, examples, etc. described herein may be combined with any one or more of the other teachings, expressions, embodiments, examples, etc. that are described herein. The following-described teachings, expressions, embodiments, examples, etc. should therefore not be viewed in isolation relative to each other. Various suitable ways in which the teachings herein may be combined will be readily apparent to those skilled in the art in view of the teachings herein. Such modifications and variations are intended to be included within the scope of the claims. 
     For clarity of disclosure, the terms “proximal” and “distal” are defined herein relative to a surgeon or other operator grasping a surgical instrument having a distal surgical end effector. The term “proximal” refers the position of an element closer to the surgeon or other operator and the term “distal” refers to the position of an element closer to the surgical end effector of the surgical instrument and further away from the surgeon or other operator. 
     I. Suprachoroidal Administration of Therapeutic Agent 
     As noted above, there may be scenarios where it is desirable to administer a therapeutic agent to an eye of a patient. By way of example only, this may be done to treat one or more ocular conditions such as macular degeneration, retinitis pigmentosa, diabetic retinopathy, other retinal disease, and/or other ocular conditions. The dispensed therapeutic agent may comprise various kinds of drugs including but not limited to small molecules, large molecules, cells, and/or gene therapies, etc. 
     Another variable in dispensing a therapeutic agent to an eye of a patient is the precise location in the eye in which to deliver the therapeutic agent. In determining the appropriate location, it may be necessary to identify where to insert a needle into the eye (e.g., somewhere between the limbus and the equator of the eye), as the needle insertion site may affect the efficacy of delivery and also the risk of trauma posed by the needle to various structures within the eye. Another potentially critical factor in determining the appropriate location for delivering a therapeutic agent to the eye may include the depth of insertion of the needle into the eye. For instance, it may be desirable to insert the needle such that the needle will deliver the therapeutic agent to the suprachoroidal space, to the subretinal space, to the vitreous region, or elsewhere in the eye. This delivery location and corresponding needle insertion depth may also affect the efficacy of delivery and the risk of trauma posed by the needle to various structures within the eye. 
     Given the relatively small size of anatomical structures within the eye, the thinness of the layers in the eye, and the procedural sensitivity to the instrument reaching the desired delivery location, it may be desirable to provide a delivery instrument that is configured to consistently promote reliable delivery of therapeutic agents to the appropriate location in the eye. In other words, it may be desirable to provide a delivery instrument that is less sensitive to the expertise and technique of an operator who might otherwise attempt to deliver the therapeutic agent using a conventional delivery instrument such as a conventional syringe. The following description provides several examples of delivery instruments that may be used to deliver a therapeutic agent to a precise target location in a patient&#39;s eye with consistency and reliability, reducing the amount of operator skill that might otherwise be necessary to reliably reach the target location with a conventional delivery instrument. While the examples described below provide delivery at a particular region between the limbus and equator of the eye, and to the suprachoroidal space of the eye, the instrument may be modified to provide delivery at any other suitable location in the eye. 
     A. Example of Instrument with Fixed Position Needle and Integral Plunger 
       FIGS.  1 - 7    depict one example of an instrument ( 10 ) that may be used to deliver a therapeutic agent to a target location in an eye of a patient. Instrument ( 10 ) of this example includes a plunger ( 20 ) that is slidably disposed with respect to a body ( 30 ). Plunger ( 20 ) includes a shaft ( 22 ). A piston ( 24 ) is located at a distal end of shaft ( 22 ) while a plunger ( 26 ) is located at the proximal end of shaft ( 22 ). Body ( 30 ) includes a barrel ( 32 ) defining a hollow interior region ( 34 ) and a hilt ( 36 ). Piston ( 24 ) is slidably positioned in hollow interior region ( 34 ) such that a liquid may be contained in the portion of interior region ( 34 ) that is distal to piston ( 24 ); and such that the liquid may be dispensed from interior region ( 34 ) by distal advancement of piston ( 24 ) relative to barrel ( 32 ). Plunger ( 20 ) and body ( 30 ) may thus be operated like a syringe, with piston ( 24 ) and hollow interior region ( 34 ) cooperating to define a fluid reservoir. 
     Instrument ( 10 ) of the present example further includes a head ( 100 ) at the distal end of barrel ( 32 ). In some versions, head ( 100 ) may be integrally formed with barrel ( 32 ). In some other versions, head ( 100 ) may be secured to barrel ( 32 ) via a conventional luer fitting, via some other kind of threaded fitting, via a snap fitting, or in any other suitable fashion as will be apparent to those skilled in the art in view of the teachings herein. As best seen in  FIGS.  2 - 5   , head ( 100 ) of the present example includes a body ( 102 ) with a distal face ( 110 ) that is bounded by three distal edges ( 120 ,  122 ,  124 ) with three corners ( 130 ,  132 ,  134 ). Each distal edge ( 120 ,  122 ,  124 ) has a curvature that is concave along a longitudinal dimension and along a lateral dimension. In this context, the term “longitudinal dimension” refers to the dimension along which the central longitudinal axis of body ( 30 ) extends; while “lateral dimension” refers to a dimension that is perpendicular to the central longitudinal axis of body ( 30 ). Distal face ( 110 ) also has a concave curvature along the longitudinal and lateral dimensions. As described in greater detail below, the curvature of upper distal edge ( 120 ) is configured to complement the curvature of a limbus (L) of a patient&#39;s eye (E); while the curvature of distal face ( 110 ) is configured to complement the curvature of the exterior surface of the patient&#39;s eye (E). 
     As best seen in  FIG.  4   , corners ( 130 ,  132 ,  134 ) are generally rounded such that corners ( 130 ,  132 ,  134 ) are atraumatic. Thus, when distal face ( 110 ) is urged against a patient&#39;s eye (E) as described in greater detail below, corners ( 130 ,  132 ,  134 ) will not inflict trauma on the patient&#39;s eye (E). 
     A needle ( 190 ) protrudes distally from distal face ( 110 ) in this example. As best seen in  FIG.  5   , needle ( 190 ) is disposed in an internal passageway ( 140 ) formed in head ( 100 ). A sharp distal tip ( 192 ) of needle ( 190 ) protrudes distally relative to distal face ( 110 ). The sharpness of distal tip ( 192 ) is provided by a bevel in this example. By way of example only, the angle of the bevel at distal tip may range from approximately 5 degrees to approximately 45 degrees; or may be approximately 15 degrees. In some versions, this bevel angle of distal tip ( 192 ) may complement the angle of the layers of tissue (S, Ch, R) in the eye (E) relative to the longitudinal axis of needle ( 190 ), such that distal tip ( 192 ) remains parallel with the boundaries of those layers as needle ( 190 ) is inserted into the eye (E). Such a bevel angle may prevent or minimize intrusion of distal tip ( 192 ) into the choroid (Ch). In some other versions, the bevel angle of distal tip ( 192 ) may be selected such that distal tip ( 192 ) is obliquely oriented relative to the boundaries of the layers of tissue (S, Ch, R) in the eye (E). Such a bevel angle may increase the likelihood of therapeutic agent reaching the suprachoroidal space (SCS) in the event that a portion of distal tip ( 192 ) remains in the sclera (S) and/or a portion of distal tip ( 192 ) overshoots the suprachoroidal space (SCS) and is disposed in the choroid (Ch). 
     A proximal end ( 196 ) of needle ( 190 ) is positioned in passageway ( 140 ), with a proximal portion ( 144 ) of passageway ( 140 ) extending proximally from proximal end ( 196 ) of needle ( 190 ) to hollow interior region ( 34 ) of barrel ( 32 ). A lumen ( 194 ) of needle ( 190 ) is in fluid communication with proximal portion ( 144 ) of passageway ( 140 ), such that fluid (e.g., including therapeutic agent) contained within hollow interior region ( 34 ) of barrel ( 32 ) may be expelled out through distal tip ( 192 ) of needle ( 190 ). In the present example, needle ( 190 ) is fixedly secured within passageway ( 140 ), such that needle ( 190 ) does not translate longitudinally within passageway ( 140 ). In some other versions, examples of which are described in greater detail below, needle ( 190 ) is operable to translate longitudinally within passageway ( 140 ) (e.g., in response to an operator input). 
     In the present example, proximal portion ( 144 ) of passageway ( 140 ) is straight, such that proximal portion ( 144 ) of passageway ( 140 ) extends along the longitudinal axis (LA) of head ( 100 ) ( FIG.  7   ). In the present example, the longitudinal axis (LA) of head ( 100 ) is coaxially aligned with the longitudinal axis of body ( 30 ). A distal portion ( 142 ) of passageway ( 140 ) extends along a curve. With needle ( 190 ) being disposed in distal portion ( 142 ) of passageway ( 140 ), this curve of distal portion ( 142 ) imparts a corresponding curve to needle ( 190 ). As shown in  FIG.  7    and as will be described in greater detail below, this curve of distal portion ( 142 ) and needle ( 190 ) provides an exit axis (EA) for needle ( 190 ) that is obliquely oriented relative to the longitudinal axis (LA). In this context, the exit axis (EA) is the axis along which distal tip ( 192 ) is oriented. The angle ( 0 ) defined between the exit axis (EA) of needle ( 190 ) and the longitudinal axis (LA) may be referred to as an exit angle. By way of example only, the exit angle ( 0 ) may range from approximately 50 degrees to approximately 89 degrees; or may be approximately 85 degrees. While the exit angle ( 0 ) is fixed in the present example, other versions may allow the operator to selectively vary the exit angle ( 0 ), as will be described in greater detail below. In some scenarios, the longitudinal axis (LA) passes through the center of the eye (E) when distal face ( 110 ) is fully seated on the eye (E). 
       FIGS.  6 - 7    show an example of instrument ( 10 ) in use. As shown in  FIG.  6   , instrument ( 10 ) is positioned such that distal face ( 110 ) abuts the outer surface (i.e., conjunctiva) of a patient&#39;s eye (E). The operator positions and orients head ( 100 ) such that upper distal edge ( 120 ) is positioned along the outer curvature of the limbus (L) of the patient&#39;s eye (E), with lower corner ( 134 ) being oriented toward the equator (Eq) of the patient&#39;s eye (E). By indexing off of the limbus (L), upper distal edge ( 120 ) may be used to ensure that needle ( 190 ) enters the eye (E) at the appropriate location between the limbus (L) and the equator (Eq) on a reliable, consistent basis. In other words, with upper distal edge ( 120 ) serving as a guide, the operator does not need to utilize calipers or other instrumentation in order to identify and mark the appropriate needle ( 190 ) insertion location relative to the limbus (L). With upper distal edge ( 120 ) indexed along the limbus (L), the operator may urge head ( 100 ) against the eye (E) until distal face ( 110 ) is fully seated against the eye (E). 
     As distal face ( 110 ) is fully seated against the eye (E), as shown in  FIG.  7   , needle ( 190 ) penetrates the sclera (S) of the eye (E) and at least a portion of distal tip ( 192 ) is positioned in the suprachoroidal space (SCS). With at least a portion of distal tip ( 192 ) positioned in the suprachoroidal space (SCS), the operator may actuate plunger ( 20 ) distally relative to body ( 30 ), thereby expelling the therapeutic agent contained in hollow interior region ( 34 ) of barrel ( 32 ) into the suprachoroidal space (SCS) via needle ( 190 ). 
     In some versions, at least a portion of distal tip ( 192 ) reaches the choroid (Ch) (e.g., contacting the choroid (Ch) without necessarily piercing the choroid (Ch)) when distal face ( 110 ) is fully seated against the eye (E). In such scenarios, the therapeutic agent contained in hollow interior region ( 34 ) of barrel ( 32 ) may nevertheless still reach the suprachoroidal space (SCS) when the operator actuates plunger ( 20 ) distally relative to body ( 30 ). The bevel angle of distal tip ( 192 ) may assist in directing fluid that is expelled from needle ( 190 ) into the suprachoroidal space (SCS), even if a portion of distal tip ( 192 ) is in contact with the choroid (Ch) at the time the fluid is expelled. Moreover, the exit angle ( 0 ) of needle ( 190 ), as provided by distal portion ( 142 ) of passageway ( 140 ) of head ( 100 ), is also configured to promote distal tip ( 192 ) reaching the suprachoroidal space (SCS) when distal face ( 110 ) is fully seated against the eye (E). The length of the portion of needle ( 190 ) that is exposed relative to distal face ( 110 ) also provides positioning of distal tip ( 192 ) in the suprachoroidal space (SCS) when distal face ( 110 ) is fully seated against the eye (E). Thus, the successful delivery of therapeutic agent to the suprachoroidal space (SCS) is influenced by a combination of the bevel angle of distal tip ( 192 ), the exit angle ( 0 ) of needle ( 190 ), and length of the portion of needle ( 190 ) that is exposed relative to distal face ( 110 ). 
     In the present example, distal tip ( 192 ) never penetrates the retina (R) and never reaches the vitreous chamber (V). Thus, distal tip ( 192 ) penetrates no further than the choroid (Ch). In some other variations, at least a portion of distal tip ( 192 ) penetrates the retina (R). Moreover, distal tip ( 192 ) may reach the vitreous chamber (V) in some variations. 
     In the procedure described above, the fluid is delivered to the anterior region of the eye (E). In some scenarios, after the fluid is delivered to the anterior region of the eye (E), at least some of the fluid (e.g., including a therapeutic agent) may eventually disperse through the suprachoroidal space (SCS) toward the posterior region of the eye (E). This may be beneficial when treating ocular conditions associated with the posterior region of the eye (E) (e.g., macular degeneration, etc.). 
     While plunger ( 20 ) is described herein as being utilized to drive fluid from hollow interior region ( 34 ) out through needle ( 190 ), any other suitable kind of fluid driving feature(s) may be used in addition to, or in lieu of, plunger ( 20 ) to serve such purposes. 
     B. Example of Instrument with Translating Needle and Sensor 
     In some instances, it may be desirable to provide a variation of instrument ( 10 ) where needle ( 190 ) is contained within head ( 100 ) until distal face ( 110 ) is fully seated against the eye (E), such that needle ( 190 ) will only be advanced distally through the sclera (S) after distal face ( 110 ) is fully seated against the eye (E). To that end,  FIGS.  8 A- 8 B  depicts an alternative example of a head ( 200 ) that may be integrated into instrument ( 10 ) as a substitute for head ( 100 ). Head ( 200 ) of this example may be configured and operable just like head ( 100 ) except for the differences described below. Head ( 200 ) of this example includes a distal face ( 210 ) that is configured just like distal face ( 110 ); and a passageway ( 240 ) extending from interior region ( 34 ) of barrel ( 32 ) to distal face ( 210 ). Head ( 200 ) of this example also includes a needle ( 290 ) with a sharp distal tip ( 292 ). 
     Unlike needle ( 190 ) of head ( 100 ), needle ( 290 ) of head ( 200 ) is configured to translate longitudinally relative to passageway ( 240 ). To provide such translation, needle ( 290 ) is coupled with an actuator ( 250 ). By way of example only, actuator ( 250 ) may include a slider, a dial, a knob, a lever, or any other suitable kind of actuator as will be apparent to those skilled in the art in view of the teachings herein. While actuator ( 250 ) is shown as being integrated into head ( 200 ), actuator ( 250 ) may instead be positioned at any other suitable location, including but not limited to body ( 30 ), etc. Regardless of the location of actuator ( 250 ), actuator ( 250 ) may be coupled with needle ( 250 ) in any suitable fashion as will be apparent to those skilled in the art in view of the teachings herein. 
     When actuator ( 250 ) is in a pre-actuated state as shown in  FIG.  8 A , distal tip ( 292 ) of needle ( 290 ) is positioned proximally in relation to distal face ( 210 ). This retraction of needle ( 290 ) into head ( 200 ) may help protect distal tip ( 292 ) from inadvertent damage; and may protect the operator and patient from inadvertent trauma that might otherwise be provided by distal tip ( 292 ). Head ( 200 ) may remain in this state up until the point at which distal face ( 210 ) is fully seated against the eye (E) as shown in  FIG.  8 A . Once distal face ( 210 ) is fully seated against the eye (E), the operator may manipulate actuator ( 250 ) to reach an actuated state as shown in  FIG.  8 B . In this actuated state, needle ( 290 ) has penetrated the sclera (S) and distal tip ( 292 ) is positioned in the suprachoroidal space (SCS). With distal tip ( 292 ) positioned in the suprachoroidal space (SCS), the operator may actuate plunger ( 20 ) distally relative to body ( 30 ), thereby expelling the therapeutic agent contained in hollow interior region ( 34 ) of barrel ( 32 ) into the suprachoroidal space (SCS) via needle ( 290 ) as described above. 
     During the transition from the state shown in  FIG.  8 A  to the state shown in  FIG.  8 B , the curved distal portion ( 242 ) of passageway ( 242 ) may guide needle ( 290 ) to achieve a desired exit angle (θ), as also described above. In addition to curved distal portion ( 242 ) of passageway ( 242 ) guiding needle ( 290 ) to achieve a desired exit angle (θ), or as an alternative to curved distal portion ( 242 ) of passageway ( 242 ) guiding needle ( 290 ) to achieve a desired exit angle (θ), needle ( 290 ) may include a resilient pre-formed bend that assists needle ( 290 ) in achieving the desired exit angle (θ) as the distal portion of needle ( 290 ) is exposed relative to distal face ( 210 ) in the actuated state. 
     As with needle ( 190 ) of head ( 100 ), the successful delivery of therapeutic agent to the suprachoroidal space (SCS) via needle ( 290 ) of head ( 200 ) is influenced by a combination of the bevel angle of distal tip ( 292 ), the exit angle (θ) of needle ( 290 ), and length of the portion of needle ( 290 ) that is exposed relative to distal face ( 210 ). In some versions, actuator ( 250 ) is configured to arrest distal advancement of needle ( 290 ) at a point where actuator ( 250 ) will prevent distal tip ( 292 ) from penetrating the retina (R) and/or reaching the vitreous chamber (V). In some versions where actuator ( 250 ) is operated manually, actuator ( 250 ) may provide the operator with tactile feedback that will enable the operator to feel when distal tip ( 292 ) has reached the suprachoroidal space (SCS), such that the operator may arrest actuation of actuator ( 250 ) once the operator feels (via actuator ( 250 )) distal tip ( 292 ) reaching the suprachoroidal space (SCS). For instance, as distal tip ( 292 ) traverses the sclera (S), the operator may feel substantial resistance from the relatively tough tissue of the sclera (S); but then a sudden reduction in resistance once distal tip ( 292 ) has fully penetrated the sclera (S) and reached the suprachoroidal space (SCS). Some versions may provide a mechanism that amplifies the tactile feedback felt through actuator ( 250 ) as distal tip ( 292 ) traverses the sclera (S) and ultimately reaches the suprachoroidal space (SCS). Such tactile feedback amplification mechanisms may include one or more gears and/or other components as will be apparent to those skilled in the art in view of the teachings herein. 
     In addition to, or as an alternative to, providing tactile feedback through actuator ( 250 ), a version of instrument ( 10 ) with head ( 200 ) may include one or more components that are operable to sense the depth position of needle ( 290 ) within the eye (E), to thereby determine when distal tip ( 292 ) has reached the suprachoroidal space (SCS). To that end, in the example shown in  FIGS.  8 A- 8 B , a strain sensor ( 260 ) is in communication with needle ( 290 ). Strain sensor ( 260 ) is operable to sense the strain on needle ( 290 ) as needle is advanced distally from the position shown in  FIG.  8 A  to the position shown in  FIG.  8 B . Strain sensor ( 260 ) is thus operable to generate a signal that is indicative of when distal tip ( 292 ) has reached the suprachoroidal space (SCS), as the strain in needle ( 290 ) will suddenly drop once distal tip ( 292 ) reaches the suprachoroidal space ( 292 ). Various suitable forms that strain sensor ( 260 ) may take will be apparent to those skilled in the art in view of the teachings herein. 
     In the present example, strain sensor ( 260 ) is in communication with a processing module ( 262 ), which is also in communication with a response module ( 264 ). Processing module ( 262 ) is operable to process signals from strain sensor ( 260 ) and drive response module ( 264 ) based on the signals from strain sensor ( 260 ). By way of example only, processing module ( 262 ) may include a microprocessor, an application specific integrated circuit (ASIC), and/or any other suitable components as will be apparent to those skilled in the art in view of the teachings herein. Response module ( 264 ) is configured to provide one or more responses in response to a command signal that is issued by processing module ( 262 ) based on strain sensor ( 260 ) indicating that distal tip ( 292 ) has reached the suprachoroidal space (SCS). Strain sensor ( 260 ), processing module ( 262 ), and response module ( 264 ) may positioned at any suitable location(s) within instrument ( 10 ), including but not limited to head ( 200 ) and/or body ( 30 ). 
     In some versions, response module ( 264 ) is operable to provide user feedback to the operator to indicate that distal tip ( 292 ) has reached the suprachoroidal space (SCS). For instance, response module ( 264 ) may include a tactile feedback feature that provides haptic feedback (e.g., a vibration, etc.) to the operator via actuator ( 250 ) and/or via body ( 30 ), etc., to indicate that distal tip ( 292 ) has reached the suprachoroidal space (SCS). In addition, or in the alternative, response module ( 264 ) may illuminate a light or provide some other form of visual feedback to indicate that distal tip ( 292 ) has reached the suprachoroidal space (SCS). In addition, or in the alternative, response module ( 264 ) may emit an audible tone or provide some other form of audible feedback to indicate that distal tip ( 292 ) has reached the suprachoroidal space (SCS). Various suitable components that may be integrated into response module ( 264 ) to provide tactile, visual, and/or audible feedback to the operator to indicate that distal tip ( 292 ) has reached the suprachoroidal space (SCS) will be apparent to those skilled in the art in view of the teachings herein. 
     In addition to providing user feedback, or in the alternative to providing user feedback, response module ( 264 ) may affect communication of fluid from interior region ( 34 ) of barrel ( 32 ) to needle ( 290 ) based on whether distal tip ( 292 ) has reached the suprachoroidal space (SCS). For instance, response module ( 264 ) may include a valve interposed between interior region ( 34 ) of barrel ( 32 ) and needle ( 290 ), with the valve remaining in a closed state until a strain sensor ( 260 ) detects distal tip ( 292 ) reaching the suprachoroidal space (SCS). With the valve in the closed state, fluid may not be communicated from interior region ( 34 ) of barrel ( 32 ) to needle ( 290 ). Once strain sensor ( 260 ) detects that distal tip ( 292 ) has reached the suprachoroidal space (SCS), processing module ( 262 ) may send a command signal to response module ( 264 ) to open the valve, thereby enabling fluid to be communicated from interior region ( 34 ) of barrel ( 32 ) to needle ( 290 ). In some versions having a valve as part of response module ( 264 ), the valve may provide misalignment between a fluid channel from interior region ( 34 ) of barrel ( 32 ) leading to needle ( 290 ), such that the misalignment provides a closed state for the valve. Once strain sensor ( 260 ) detects distal tip ( 292 ) reaching the suprachoroidal space (SCS), processing module ( 262 ) may activate the valve of response module ( 264 ) to provide alignment between the fluid channel from interior region ( 34 ) of barrel ( 32 ) and needle ( 290 ), such that the alignment provides an open state for the valve. 
     In addition, or in the alternative, response module ( 264 ) may include a pump or other feature that is operable to actively drive fluid from interior region ( 34 ) of barrel ( 32 ) to needle ( 290 ) in response to a signal indicating that distal tip ( 292 ) has reached the suprachoroidal space (SCS). In such versions, plunger ( 20 ) may be omitted. Various suitable components that may be integrated into response module ( 264 ) to provide the above-describe fluid communication effects will be apparent to those skilled in the art in view of the teachings herein. Similarly, other suitable kinds of responses that may be carried out by response module ( 264 ), and components that may be incorporated into response module ( 264 ) for carrying out such other responses, will be apparent to those skilled in the art in view of the teachings herein. 
     While strain sensor ( 260 ), processing module ( 262 ), and response module ( 264 ) are described above in the context of head ( 200 ), such components are optional and may be omitted in some versions of instrument ( 10 ) that include head ( 200 ). Similarly, the other variations of instrument ( 10 ) that are described herein, including but not limited to the variations including head ( 100 ,  300 ,  400 ,  500 ,  700 ) may include strain sensor ( 260 ), processing module ( 262 ), and response module ( 264 ), if desired. 
     C. Example of Instrument with Translating Pre-Curved Needle 
     In the above-described examples of heads ( 100 ,  200 ), the obliquely oriented exit axis (EA) of needle ( 190 ,  290 ) is provided by the curved distal portion ( 142 ,  242 ) of passageway ( 140 ,  240 ). In such versions, needle ( 190 ,  290 ) may in fact be resiliently biased to assume a straight configuration, with the curved distal portion ( 142 ,  242 ) of passageway ( 140 ,  240 ) imparting lateral stress on needle ( 190 ,  290 ) in order to deform needle ( 190 ,  290 ) to achieve the oblique exit angle (θ) from distal face ( 110 ,  210 ) of head ( 100 ,  200 ). In some other variations, the needle itself may be resiliently biased to have a bent distal end, such that the needle is pre-curved. An example of such a variation is shown in  FIGS.  9 A- 9 B . 
       FIGS.  9 A- 9 B  show an alternative example of a head ( 300 ) that may be integrated into instrument ( 10 ) as a substitute for head ( 100 ). Head ( 300 ) of this example may be configured and operable just like head ( 100 ) except for the differences described below. Head ( 300 ) of this example includes a distal face ( 310 ) and a passageway ( 340 ) extending from interior region ( 34 ) of barrel ( 32 ) to distal face ( 310 ). Head ( 300 ) of this example also includes a needle ( 390 ) with a sharp distal tip ( 392 ). Needle ( 390 ) is configured to translate longitudinally relative to passageway ( 340 ). To provide such translation, needle ( 390 ) is coupled with an actuator ( 350 ). By way of example only, actuator ( 350 ) may be configured and operable like actuator ( 250 ) described above. Other suitable configurations and operabilities for actuator ( 350 ) will be apparent to those skilled in the art in view of the teachings herein. 
     In the present example, distal face ( 310 ) is substantially flat, such that distal face ( 310 ) is not contoured to complement the curvature of the eye (E). In some other versions, distal face ( 310 ) is in fact contoured to complement the curvature of the eye (E). Distal face ( 310 ) may thus be configured and operable similar to distal face ( 110 ,  210 ) of head ( 110 ,  210 ). In versions where distal face ( 310 ) is flat, the operator may pivot head ( 300 ) at the interface between distal face ( 310 ) and the eye (E) to effectively adjust the angle at which needle ( 390 ) enters the eye (E). Regardless of whether distal face ( 310 ) is flat or contoured, distal face ( 310 ) may include an upper distal edge or other guidance feature that is configured to facilitate indexing of head ( 300 ) relative to the limbus (L) of the eye (E) to thereby ensure that needle ( 390 ) enters the eye at the desired position between the limbus (L) and the equator (Eq). 
     The entire length of passageway ( 340 ) is straight in this example. In some versions, the entire length of passageway ( 340 ) is coaxial with the central longitudinal axis of head ( 300 ) and/or body ( 30 ). In some versions where the entire length of passageway ( 340 ) is straight, the resilient bias in the distal portion ( 394 ) of needle ( 390 ) is enough to achieve the desired oblique exit axis (EA) as distal portion ( 394 ) of needle ( 390 ) exits distal face ( 310 ) ( FIG.  9 B ). In some other versions, a distal portion of passageway ( 340 ) is curved or otherwise bent. For instance, a distal portion of passageway ( 340 ) may be configured similar to distal portion ( 142 ,  242 ) of passageway ( 140 ,  240 ). In such versions, the resilient bias in the distal portion ( 394 ) of needle ( 390 ), together with deformation induced by a curved distal portion of passageway ( 340 ), may provide the desired oblique exit axis (EA) as distal portion ( 394 ) of needle ( 390 ) exits distal face ( 310 ). 
     When actuator ( 350 ) is in a pre-actuated state as shown in  FIG.  9 A , distal tip ( 392 ) of needle ( 390 ) is positioned proximally in relation to distal face ( 310 ). This retraction of needle ( 390 ) into head ( 300 ) may help protect distal tip ( 392 ) from inadvertent damage; and may protect the operator and patient from inadvertent trauma that might otherwise be provided by distal tip ( 392 ). With passageway ( 340 ) being straight in this example, and with distal portion ( 394 ) being resiliently biased to achieve a curved configuration, passageway ( 340 ) may hold distal portion ( 394 ) in a stressed state while actuator ( 350 ) is in a pre-actuated state as shown in  FIG.  9 A . Head ( 300 ) may remain in this state up until the point at which distal face ( 310 ) is placed in contact with the eye (E) as shown in  FIG.  9 A . 
     Once distal face ( 310 ) is in sufficient contact with the eye (E), the operator may manipulate actuator ( 350 ) to reach an actuated state as shown in  FIG.  9 B . During such actuation, as the distal portion ( 394 ) exits distal face ( 310 ), the resilient bias of distal portion ( 394 ) will cause the length of distal portion ( 394 ) that is exposed relative to distal face ( 310 ) to bend, thereby causing distal tip ( 392 ) to deflect laterally along an obliquely oriented exit axis (EA). During this actuation, needle ( 390 ) penetrates the sclera (S) and distal tip ( 392 ) is eventually positioned in the suprachoroidal space (SCS). In some versions, the pre-formed bend in distal portion ( 394 ) of needle ( 390 ) may be carefully configured to promote the bevel angle of distal tip ( 392 ) remaining substantially parallel with the boundaries of the layers of tissue (S, Ch, R) in the eye (E). Regardless of the configuration of distal tip ( 392 ), the pre-formed bend in distal portion ( 394 ) of needle ( 390 ) may be carefully configured to promote entry of distal tip ( 392 ) into the suprachoroidal space (SCS) at an optimal angle. With distal tip ( 392 ) positioned in the suprachoroidal space (SCS), the operator may actuate plunger ( 20 ) distally relative to body ( 30 ), thereby expelling the therapeutic agent contained in hollow interior region ( 34 ) of barrel ( 32 ) into the suprachoroidal space (SCS) via needle ( 390 ) as described above. 
     In some versions of head ( 300 ), needle ( 390 ) is formed of nitinol. Alternatively, any other suitable material or combination of materials may be used to form needle ( 390 ). Other suitable material(s) that may be used to form needle ( 390 ) will be apparent to those skilled in the art in view of the teachings herein. 
     D. Example of Instrument with Adjustable Angle Needle 
     In the examples described above, a curved distal portion ( 142 ,  242 ) of passageway ( 140 ,  240 ) and/or a pre-formed bend in distal portion ( 394 ) of needle ( 390 ) is used to achieve a desired exit angle (θ) for needle ( 190 ,  290 ,  390 ). In the example of heads ( 100 ,  200 ), the curvature of curved distal portion ( 142 ,  242 ) of passageway ( 140 ,  240 ) may be fixed, such that the operator may be unable to make adjustments to the exit angle (θ) if such adjustments are necessary to reach the suprachoroidal space (SCS) of a particular patient at hand. Similarly, in the example of head ( 300 ), the curvature of the pre-formed bend in distal portion ( 394 ) of needle ( 390 ) may be fixed, such that the operator may be unable to make adjustments to the exit angle (θ) if such adjustments are necessary to reach the suprachoroidal space (SCS) of a particular patient at hand. It may therefore be desirable to provide a variation of instrument ( 10 ) that allows the operator to adjust the exit angle (θ) of a needle if such adjustments are necessary to reach the suprachoroidal space (SCS) of a particular patient at hand. 
       FIG.  10    depicts an alternative example of a head ( 400 ) that may be integrated into instrument ( 10 ) as a substitute for head ( 100 ). Head ( 400 ) of this example may be configured and operable just like head ( 100 ) except for the differences described below. Head ( 400 ) of this example includes a distal face ( 410 ) and an adjustment member ( 470 ) rotatably supported by a body ( 402 ) of head ( 400 ). Distal face ( 410 ) is shown as being flat in the present example, though other versions of distal face ( 410 ) may be contoured to complement the curvature of the eye (E) (e.g., similar to distal face ( 110 ,  210 ). As will be described in greater detail below, a needle ( 490 ) passes through adjustment member ( 470 ), with adjustment member ( 470 ) being operable to adjust the exit angle (θ) of needle ( 490 ). In some versions, the longitudinal position of needle ( 490 ) is fixed relative to the body ( 402 ) of head ( 400 ) (e.g., similar to the relationship between needle ( 190 ) and body ( 102 ) of head ( 100 )). In some other versions, an actuator (e.g., similar to actuator ( 290 ,  390 )) is operable to drive longitudinal translation of needle ( 490 ) relative to body ( 402 ) of head ( 400 ). 
     Adjustment member ( 470 ) includes a wheel ( 472 ) with an axle ( 474 ). Wheel ( 472 ) is pivotably coupled with body ( 402 ) via axle ( 474 ) such that wheel ( 472 ) is rotatable relative to body ( 402 ) about the rotation axis defined by axle ( 474 ). A portion of wheel ( 472 ) is exposed relative to body ( 402 ) to thereby enable an operator to engage wheel ( 472 ) with a finger or thumb and thereby rotate wheel ( 472 ) relative to body ( 402 ). Wheel ( 472 ) further defines a passageway ( 476 ). A needle ( 490 ) is disposed in passageway ( 476 ). In the present example, passageway ( 476 ) is positioned such that passageway ( 476 ) perpendicularly intersects the rotation axis defined by axle ( 474 ). In other versions, passageway ( 476 ) may be offset in relation to the rotation axis defined by axle ( 474 ) such that the rotation axis defined by axle ( 474 ) does not intersect passageway ( 476 ). 
     As shown in  FIG.  11   , when the operator rotates wheel ( 472 ) relative to body ( 402 ), the operator may effectively reposition needle ( 490 ) at various exit angles ( 0 ), thereby achieving a variety of alternative use positions ( 490   a ,  490   b ,  490   c ). In alternative use position ( 490   c ), distal tip ( 492   c ) is positioned entirely in the sclera (S), such that therapeutic agent expelled via distal tip ( 492   c ) may not necessarily reach the suprachoroidal space (SCS) In alternative use position ( 490   b ), distal tip ( 492   b ) is closer to reaching the suprachoroidal space (SCS), but is still positioned entirely in the sclera (S), such that therapeutic agent expelled via distal tip ( 492   b ) may again not necessarily reach the suprachoroidal space (SCS). However, in alternative use position ( 490   a ), distal tip ( 492   a ) is within the suprachoroidal space (SCS), such that therapeutic agent expelled via distal tip ( 492   a ) will effectively reach the suprachoroidal space (SCS). 
     During use of an instrument ( 10 ) incorporating head ( 400 ), the operator may advance distal face ( 410 ) into engagement with the eye ( 410 ), with adjustment member ( 470 ) set to provide a first exit angle (θ) for needle ( 490 ). In versions where the longitudinal position of needle ( 490 ) is fixed relative to body ( 402 ), the operator may advance distal tip ( 492 ) into the eye (E) simply by urging distal face ( 410 ) into contact with the eye (E). In versions where an actuator is used to longitudinally translate needle ( 490 ) relative to body ( 402 ), the operator may first bring distal face ( 410 ) into contact with the eye (E), then operate the actuator to advance distal tip ( 492 ) into the eye (E). In either case, the operator may rely on any suitable form of feedback to determine whether the advanced distal tip ( 492 ) successfully reached the suprachoroidal space (SCS). By way of example only, the operator may rely on tactile feedback via the hand grasping instrument ( 10 ). Alternatively, the operator may rely on feedback from another feature like response module ( 264 ). Other suitable ways in which the operator may determine whether the advanced distal tip ( 492 ) successfully reached the suprachoroidal space (SCS) will be apparent to those skilled in the art in view of the teachings herein. 
     If the operator determines that the advanced distal tip ( 492 ) has not successfully reached the suprachoroidal space (SCS), the operator may retract needle ( 490 ) from the eye (E) and then manipulate wheel ( 472 ) to adjust the exit angle (θ). To assist in this adjustment process, wheel ( 472 ) of the present example includes indicia ( 478 ) and body ( 478 ) defines a window ( 404 ) through which indicia ( 478 ) may be visually observed. Indicia ( 478 ) may indicate the exit angle (θ) associated with the current angular position of wheel ( 472 ). Wheel ( 472 ) and body ( 402 ) may further include detents or other features that assist in releasably maintaining wheel ( 472 ) at certain discrete angular positions associated with corresponding exit angles ( 0 ). Once the operator has adjusted the exit angle (θ) by manipulating wheel ( 472 ), the operator may again advance distal tip ( 492 ) into the eye (E) at the adjusted exit angle (θ). The above-described process may be repeated until the operator determines that distal tip ( 492 ) has successfully reached the suprachoroidal space (SCS). Once the operator determines that distal tip ( 492 ) has successfully reached the suprachoroidal space (SCS), the operator may administer the therapeutic agent to the suprachoroidal space (SCS) via the needle as described above. 
     While a wheel ( 472 ) is described above as an example of a structure that may be used to provide adjustability of the exit angle (θ) of a needle ( 490 ), any other suitable kind of structures may be used. Other suitable structures that may be used to provide adjustability of the exit angle (θ) of a needle ( 490 ) will be apparent to those skilled in the art in view of the teachings herein. While adjustment member ( 470 ) is described herein in the context of head ( 400 ), adjustment member ( 470 ) or variations thereof may be readily incorporated into any of the other various heads ( 100 ,  200 ,  300 ,  500 ,  800 ) described herein. 
     E. Example of Instrument with Voltage Sensing 
     As described above in the context of head ( 200 ), a strain sensor ( 260 ) may be used to detect the position of needle ( 290 ) within the layers of tissue (S, Ch, R) in the eye (E) as a function of the stress encountered by needle ( 290 ) during advancement of needle ( 290 ) into the eye (E).  FIG.  12    depicts another example of how an instrument may detect the position of needle ( 290 ) within the layers of tissue (S, Ch, R) in the eye (E). In particular,  FIG.  12    depicts a head ( 500 ) that may be integrated into instrument ( 10 ) as a substitute for head ( 100 ). Head ( 500 ) of this example may be configured and operable just like head ( 100 ) except for the differences described below. Head ( 500 ) of this example includes a needle ( 590 ), a set of distal electrodes ( 504 ), a processing module ( 580 ), and a response module ( 582 ). Needle ( 590 ) is formed of an electrically conductive material such that needle ( 590 ) is operable to serve as an electrode (e.g., at a different polarity from electrodes ( 504 )). Processing module ( 580 ) is in electrical communication with needle ( 590 ) and electrodes ( 504 ). 
     Electrodes ( 504 ) are positioned and configured to contact tissue of the eye (E) as head ( 500 ) is urged into contact with the eye (E). In some versions, electrodes ( 504 ) include one or more electrodes ( 504 ) that are spaced apart from each other in an angularly spaced array about the longitudinal axis of body ( 502 ) or needle ( 590 ). In some other versions, electrodes ( 504 ) are provided in the form of one or more annular electrodes that is/are coaxially positioned about the longitudinal axis of body ( 502 ) or needle ( 590 ). Other suitable forms that electrodes ( 504 ) may take will be apparent to those skilled in the art in view of the teachings herein. 
     When needle ( 590 ) and electrodes ( 504 ) are simultaneously in contact with tissue, processing module ( 580 ) may detect an electrical potential or voltage in the tissue.  FIG.  13    shows a plot ( 600 ) depicting an example of how such voltage may vary based on the position of distal tip ( 592 ) of needle ( 590 ) within the layers of tissue (S, Ch, R) in the eye (E). During initial insertion of needle ( 590 ) into the eye (E), a first portion ( 602 ) of the plot ( 600 ) shows a relatively low voltage as distal tip ( 592 ) traverses the sclera (S). As distal tip ( 592 ) reaches the suprachoroidal space (SCS), the plot ( 600 ) shows a sharp increase ( 604 ) in voltage, with the final portion ( 606 ) of plot ( 600 ) showing a relatively high voltage with distal tip ( 592 ) in the suprachoroidal space (SCS). 
     In some versions, needle ( 590 ) is configured to translate longitudinally relative body ( 502 ) such that distal tip ( 592 ) is retracted proximally in body ( 502 ) when distal electrodes ( 504 ) make initial contact with the eye (E). Once distal electrodes ( 504 ) are in contact with the eye (E), needle ( 590 ) may be advanced distally into the eye (E) as described in other examples herein, with processing module ( 580 ) tracking the voltage value as needle ( 590 ) is advanced distally. 
     When processing module ( 580 ) detects a voltage associated with distal tip ( 592 ) successfully reaching the suprachoroidal space (SCS) (e.g., consistent with the final portion ( 606 ) of plot ( 600 ) in  FIG.  13   ), processing module ( 580 ) may activate response module ( 582 ) to provide a corresponding response. Response module ( 582 ) may be configured and operable like response module ( 264 ) described above. Thus, response module ( 582 ) may provide tactile, visual, and/or audible feedback to the operator to indicate that distal tip ( 592 ) has reached the suprachoroidal space (SCS); may open a valve, activate a pump, and/or provide other fluid communication effects in response to distal tip ( 592 ) reaching the suprachoroidal space (SCS); and/or provide any other suitable kind(s) of response(s) as will be apparent to those skilled in the art in view of the teachings herein. 
     While electrodes ( 504 ), needle ( 590 ), and processing module ( 580 ) are described herein as being used to track changes in voltage as a function of the depth of insertion of needle ( 590 ) into the eye (E), these components may instead be used to track any other suitable electrical parameter (e.g., impedance or electrical resistance, etc.) as a function of the depth of insertion of needle ( 590 ) into the eye (E), as will be apparent to those skilled in the art in view of the teachings herein. While electrodes ( 504 ), processing module ( 580 ), and response module ( 582 ) are described herein in the context of head ( 500 ), these components or variations thereof may be readily incorporated into any of the other various heads ( 100 ,  200 ,  300 ,  400 ,  800 ) described herein. 
     F. Example of Instrument with Sclera Tensioning Feature 
     In some scenarios, an operator may inadvertently press the head of an instrument against an eye (E) with too much force, which may cause deformation in the layers of the eye (E). An example of such a scenario is shown in  FIG.  14   . As shown in  FIG.  14   , a head ( 700 ) of an instrument includes a needle ( 790 ) projecting distally from a body ( 702 ), with a distal face ( 710 ) being pressed into the eye (E) with substantial force. This pressure imposed by distal face ( 710 ) has caused the sclera (S) to deform and thereby press against the choroid (Ch), thereby compressing the suprachoroidal space (SC). While distal tip ( 792 ) of needle ( 790 ) may still be successfully positioned in the suprachoroidal space (SCS) and thereby delivery therapeutic agent to the suprachoroidal space (SCS), the compressed state of the suprachoroidal space (SCS) may adversely impact the ability of the therapeutic agent to be received and dispersed within the suprachoroidal space (SCS). 
     Thus, with a configuration of head ( 700 ) similar to that shown in  FIG.  14   , the success of the procedure may be substantially dependent on the skill of the operator, based on the extent to which the operator can avoid creating the conditions depicted in  FIG.  14    by pressing head ( 700 ) into the eye (E) with too much force. It may therefore be desirable to provide an alternative configuration for head ( 700 ) that is less sensitive to the skill of the operator, such that the suprachoroidal space (SCS) is less likely to be compressed even if the operator presses the head into the eye (E) with substantial force.  FIG.  15    depicts an example of such an alternative. 
     In particular,  FIG.  15    depicts a head ( 800 ) that may be integrated into instrument ( 10 ) as a substitute for head ( 100 ). Head ( 800 ) of this example may be configured and operable just like head ( 100 ) except for the differences described below. Head ( 800 ) of this example includes a needle ( 890 ) extending distally from a distal surface ( 810 ), a first distal projection ( 830 ), and a second distal projection ( 840 ). Distal projections ( 830 ,  840 ) are laterally offset from needle ( 890 ). Each distal projection ( 830 ,  840 ) includes an eye engaging surface ( 832 ,  842 ). Distal surface ( 810 ) is located proximally in relation to eye engaging surfaces ( 832 ,  842 ). Thus, when head ( 800 ) is pressed against an eye (E) as shown in  FIG.  15   , eye engaging surfaces ( 832 ,  842 ) engage the sclera (S) while distal surface ( 810 ) remains recessed relative to the sclera (S), with a gap ( 824 ) being defined between distal surface ( 810 ) and the sclera (S). With eye engaging surfaces ( 832 ,  842 ) being laterally offset from needle ( 890 ), the pressure applied to the eye (E) by head ( 800 ) is laterally offset from the point at which needle ( 890 ) is inserted into the eye (E). Moreover, eye engaging surfaces ( 832 ,  842 ) maintain tension in the sclera (S); and the pressure imposed by head ( 800 ) on the eye (E) is distributed over a larger surface area of the eye (E) as compared to the pressure from head ( 700 ). Thus, the sclera (S) is less likely to deform in the region where needle ( 890 ) enters the sclera (S); and head ( 800 ) does not tend to compress the suprachoroidal space (SCS) in the region where distal tip ( 892 ) of needle ( 890 ) dispenses therapeutic agent to the suprachoroidal space (SCS). This may improve the ability of the therapeutic agent to be received and dispersed within the suprachoroidal space (SCS), as compared to the scenario with head ( 700 ) depicted in  FIG.  14   . 
     While head ( 800 ) of the present example is described as including two distal projections ( 830 ,  840 ), head ( 800 ) may include any other suitable number of distal projections ( 830 ,  840 ). For instance, head ( 800 ) may include three or more distal projections that are angularly spaced apart from each other about a central longitudinal axis of head ( 800 ) and/or needle ( 890 ). As another example, distal projections ( 830 ,  840 ) may be substituted or supplemented with a single distal projection that continuously spans a full circumference about needle ( 890 ), such that the single distal projection and distal surface ( 810 ) together define a cup-like shape. Other suitable configurations and variations will be apparent to those skilled in the art in view of the teachings herein. While distal projections ( 830 ,  840 ) are described herein in the context of head ( 800 ), distal projections ( 830 ,  840 ) or variations thereof may be readily incorporated into any of the other various heads ( 100 ,  200 ,  300 ,  400 ,  500 ) described herein. 
     G. Example of Instrument with Fixed Position Needle and Flexible Conduit for Syringe Coupling 
     In some scenarios, it may be desirable to utilize a separate syringe to deliver fluid via an instrument to a suprachoroidal space (SCS), where the delivery instrument is coupled with the syringe via a flexible conduit. This may enable the operator to grasp the delivery instrument with one hand while grasping the syringe with another hand. Alternatively, this may enable a first operator to grasp the delivery instrument with one hand and another operator (e.g., an assistant) to grasp the syringe. In either scenario, it may be easier for the delivery instrument operator to maintain the position, orientation, and stabilization of the delivery instrument if the operator does not need to use the same hand that is grasping the delivery instrument to perform other functions (e.g., driving a plunger to deliver fluid, etc.).  FIGS.  16 - 18 C  show an example of a delivery instrument ( 900 ) that may be grasped and manipulated by a single hand of an operator while another hand of the same operator (or the hand of another operator) grasps and operates a syringe ( 980 ). 
     As shown in  FIG.  16   , instrument ( 900 ) of this example includes a shaft ( 910 ) that is configured for grasping with a single hand of the operator (e.g., via a pencil grip). A proximal end of shaft ( 910 ) includes an integral marking assembly ( 920 ), which includes a pair of proximally extending marking prongs ( 922 ) that are laterally spaced apart from each other. Prongs ( 922 ) of this example are blunt or otherwise atraumatic, such that prongs ( 922 ) may be pressed against a patient&#39;s eye (E) without piercing the sclera (S). The distal end of shaft ( 910 ) includes a head ( 930 ) that is used to engage an eye (E) of a patient to thereby deliver fluid (e.g., therapeutic agent, etc.) to the eye (E) as described herein. Head ( 930 ) includes a concave distal face ( 932 ). Distal face ( 932 ) is oriented generally transversely relative to the longitudinal axis of shaft ( 910 ). Distal face ( 932 ) is bounded by an upper edge region ( 934 ) and a lower edge region ( 936 ), with regions ( 934 ,  936 ) together defining an outer perimeter of distal face ( 932 ). Similar to distal face ( 110 ) of head ( 100 ) described above, distal face ( 932 ) of head ( 930 ) has a concave curvature along longitudinal and lateral dimensions. The curvature of distal face ( 932 ) is configured to complement the curvature of the exterior surface of the patient&#39;s eye (E). 
     Instrument ( 900 ) of the present example further includes a laterally facing guidance feature ( 940 ) and a laterally extending grip feature ( 950 ) along an intermediate region of shaft ( 910 ). Laterally facing guidance feature ( 940 ) includes a concave face ( 942 ) having a curvature that is configured to complement the curvature of a limbus (L) of a patient&#39;s eye (E). As described in greater detail below, this configuration may enable concave face ( 942 ) to be used to visually facilitate alignment of instrument ( 900 ) relative to the eye (E). Grip feature ( 950 ) is configured to promote grasping of instrument ( 900 ) with a single hand, particularly using a pencil grip. Alternatively, instrument ( 900 ) may be grasped in any other suitable fashion. A laterally facing surface ( 952 ) extends between concave face ( 942 ) of laterally facing guidance feature ( 940 ) and upper edge region ( 934 ) of distal face ( 932 ). Surface ( 952 ) is obliquely oriented relative to the longitudinal axis of shaft ( 910 ) and has a concave curvature. Surface ( 952 ) is configured to avoid or minimize contact with the cornea of the eye (E) during use of instrument ( 900 ), as will be described in greater detail below. 
     A needle ( 960 ) extends distally from head ( 930 ). A portion of needle ( 960 ) is positioned in a laterally presented recess or trough ( 938 ) that is formed in distal face ( 932 ). Needle ( 960 ) has a sharp, beveled tip ( 962 ) that is exposed relative to head ( 930 ). Needle ( 960 ) may comprise stainless steel and/or any other suitable material(s). In the present example, needle ( 960 ) is resiliently flexible, such that the region of needle ( 960 ) that is exposed relative to head ( 930 ) may deform laterally (e.g., as described below with reference to  FIG.  19   ). In some scenarios, a portion of needle ( 960 ) may flex laterally out of trough ( 938 ) and away from trough ( 938 ). Trough ( 938 ) may thus provide clearance for lateral deformation of needle ( 960 ). Needle ( 960 ) may be approximately 30 gauge or any other suitable size. In this example, needle ( 960 ) is straight and extends along a needle axis (NA) that is parallel with the longitudinal axis of shaft ( 912 ). In some versions, the needle axis (NA) is coaxial with the longitudinal axis of shaft ( 912 ). In some other versions, the needle axis is laterally offset from (yet still parallel with) the longitudinal axis of shaft ( 912 ). In the present example, the position of needle ( 960 ) relative to shaft ( 910 ) is fixed, such that needle ( 960 ) does not translate longitudinally relative to shaft ( 910 ). In some other versions, needle ( 960 ) is translatable relative to shaft ( 910 ) (e.g., between a proximal retracted position and a distal exposed position). 
     A flexible conduit ( 970 ) extends from shaft ( 910 ) and provides a path for fluid communication with the lumen of needle ( 960 ) as will be described in greater detail below. Flexible conduit ( 970 ) may comprise a transparent flexible tube or may take any other suitable form. The interior of shaft ( 910 ) may define a lumen providing a pathway for fluid communication from flexible conduit ( 970 ) to needle ( 960 ). In some variations, flexible conduit ( 970 ) is received such a lumen and connects with a hub at the proximal end of needle ( 960 ). In some other variations, flexible conduit ( 970 ) distally terminates in the lumen in shaft ( 910 ) and needle ( 960 ) proximally terminates in shaft ( 910 ), such that fluid is communicated from flexible conduit ( 970 ) to needle ( 960 ) via the lumen. Alternatively, flexible conduit ( 970 ) may be fluidically coupled with needle ( 960 ) in any other suitable fashion. 
     As shown in  FIG.  17   , instrument ( 900 ) may be positioned in relation to an eye (E) such that distal face ( 932 ) of head ( 930 ) is fully seated against the exterior surface of the eye (E). Needle ( 960 ) enters the sclera (S) at an entry point (EP) that is a predetermined distance from the limbus (L) of the eye (E). By way of example only, this predetermined distance from the limbus (L) to the entry point (EP) ranges from approximately 3.0 mm to approximately 4.0 mm; or may be approximately 3.5 mm. 
     In some scenarios, this predetermined distance from the limbus (L) to the entry point (EP) is achieved by the operator aligning upper edge region ( 934 ) of head ( 930 ) along the limbus (L), such that upper edge region ( 934 ) serves as an indexing feature. In addition, or in the alternative, this predetermined distance may also be achieved using marking prongs ( 922 ). The spacing between marking prongs ( 922 ) may be selected to indicate the appropriate distance between the limbus (L) and the entry point (EP), such that marking assembly ( 920 ) may be used like calipers. In some such scenarios, the operator may first press marking prongs ( 922 ) against a pad having biocompatible ink to thereby ink the prongs ( 922 ); then press the inked marking prongs ( 922 ) against the eye (E) to thereby mark the entry point (EP) with ink. In some other scenarios, the operator may press marking prongs ( 922 ) against the eye (E), without ink on marking prongs ( 922 ), with sufficient force to cause a marking indentation in the sclera (S) (without piercing the sclera (S)). Alternatively, marking prongs ( 922 ) may be used in any other suitable fashion. Alternatively, still, the entry point (EP) may be marked in any other suitable fashion. 
     Still referring to the arrangement shown in  FIG.  17   , due to the structural configuration and arrangement of distal face ( 932 ) and needle ( 960 ), the needle axis (NA) defines a predetermined angle (θ) with a tangent line (TL) at the entry point (EP). The tangent line (TL) is tangent to the exterior surface of the eye (E) at the entry point (EP). In the present example, this predetermined angle (θ) is oblique. By way of example only, the angle (θ) may range from approximately 0 degrees to approximately 40 degrees; or may be approximately 5 degrees. While the angle (θ) is fixed in the present example, other versions may allow the operator to selectively vary the angle (θ), as described in various examples provided above. 
     With distal face ( 932 ) of head ( 930 ) fully seated against the exterior surface of the eye (E), needle ( 960 ) passes fully through the sclera (S) such that tip ( 962 ) is positioned in the suprachoroidal space (SCS). The length of needle ( 960 ) that is exposed relative to distal face ( 932 ), in view of the angle (θ), is selected to allow tip ( 962 ) to reach the suprachoroidal space (SCS) without penetrating the choroid (Ch). However, in some scenarios, tip ( 962 ) may incidentally engage the choroid (Ch) without passing fully through the choroid (Ch) and reaching the subretinal space between the choroid (Ch) and the retina (R). By way of example only, the length of needle ( 960 ) that is exposed relative to distal face ( 932 ) may range from approximately 0.5 mm to approximately 5.0 mm; or may be approximately 1.25 mm. The length of needle ( 960 ) that is exposed relative to distal face ( 932 ), in combination with the oblique angle (θ) at which needle ( 960 ) enters the eye (E), may reduce the risk of needle ( 960 ) undesirably traversing the choroid (Ch). In other words, providing an oblique angle (θ) for entry of needle ( 960 ) may provide less risk of undesirable choroid (Ch) penetration as compared to the risk of undesirable choroid (Ch) penetration that may be presented by a perpendicular angle (θ) for entry of needle ( 960 ). Similarly, the length of needle ( 960 ) that is exposed relative to distal face ( 932 ), in combination with the oblique angle (θ) at which needle ( 960 ) enters the eye (E), may reduce the risk of needle ( 960 ) only reaching an insertion depth where tip ( 962 ) remains in the sclera (S), without reaching the suprachoroidal space (SCS). The configuration and orientation of needle ( 960 ) may thus accommodate different sclera (S) thicknesses in different patients, with little to no risk of needle ( 960 ) being inserted to a depth that is too shallow (i.e., not reaching the suprachoroidal space (SCS)) or too deep (i.e., passing completely through the choroid (Ch) and perhaps even the retina (R)). 
     In the present example, the bevel angle of tip ( 962 ) is selected to promote communication of fluid out from tip ( 962 ) into the suprachoroidal space (SCS). By way of example only, this bevel angle may range from approximately 8 degrees to approximately 20 degrees; or may be approximately 14 degrees. Tip ( 962 ) may have a tri-bevel configuration or any other suitable configuration. The bevel of tip ( 962 ) in the present example is angularly oriented to face the choroid (C), to thereby promote communication of fluid to the suprachoroidal space (SCS) as the fluid exits tip ( 962 ) when tip is positioned at or near the suprachoroidal space (SCS). 
       FIGS.  18 A- 18 C  show instrument ( 900 ) coupled with a syringe ( 980 ) for use in a procedure to deliver fluid (e.g., therapeutic agent, etc.) to an eye (E). Syringe ( 980 ) of this example includes a conventional syringe, such that syringe ( 980 ) includes a barrel ( 982 ) containing fluid, a distal luer fitting ( 984 ), and a plunger ( 986 ) that is slidably disposed in barrel ( 982 ). Conduit ( 970 ) includes a luer fitting ( 972 ) that removably couples with luer fitting ( 984 ) of syringe ( 980 ). An operator may thus drive fluid from barrel ( 982 ) of syringe ( 980 ) into conduit ( 970 ), and thereby drive the fluid to needle ( 960 ) of instrument ( 900 ), by advancing plunger ( 986 ) distally relative to barrel ( 982 ). 
     As shown in  FIG.  18 A , the operator may initially position instrument ( 900 ) relative to the eye (E) by positioning distal tip ( 962 ) of needle ( 960 ) at the desired entry point (EP). As noted above, marking assembly ( 920 ) may be used like calipers to mark the entry point (EP) relative to the limbus (L) before the operator positions distal tip ( 962 ) of needle ( 960 ) at the entry point (EP). At the stage shown in  FIG.  18 A , the operator may refrain from fully advancing needle ( 960 ) through the sclera (S). For instance, the operator may just initially penetrate the sclera (S) with distal tip ( 962 ) at this stage, or minimally contact the sclera (S) with distal tip ( 962 ), to maintain the position of distal tip ( 962 ) at the entry point (EP) before fully advancing distal tip ( 962 ) into the eye (E) as described below. At this stage, head ( 930 ) is still spaced away from the eye (E), such that the only portion of instrument ( 900 ) contacting the eye (E) is needle ( 960 ). 
     Once the operator has appropriately positioned distal tip ( 962 ) at the entry point (E), the operator may then pivot instrument ( 900 ) relative to the eye (E), with the interface of needle ( 960 ) and the entry point (EP) providing the pivot point for such pivotal motion. The operator may pivot instrument ( 900 ), while visually observing instrument ( 900 ) along the length of shaft ( 910 ) from the proximal end, until instrument ( 900 ) reaches a point where upper edge region ( 934 ) of distal face ( 932 ) is generally aligned with the limbus (L). As noted above, concave face ( 942 ) of guidance feature ( 940 ) may facilitate visual observation of upper edge region ( 934 ) of distal face ( 932 ) in relation to the limbus (L) during this pivotal movement. Upon reaching the appropriate pivotal alignment of instrument ( 900 ) in relation to the eye (E), the operator may complete distal advancement of instrument ( 900 ) relative to the eye (E) until distal face ( 932 ) is fully seated against the eye (E), as shown in  FIG.  18 B . With distal face ( 932 ) fully seated against the eye (E), needle ( 960 ) may be positioned such that distal tip ( 962 ) is located precisely at (or substantially at) the suprachoroidal space (SCS) as shown in  FIG.  17   . In some scenarios, as described below with reference to  FIG.  19   , the sclera (S) may deform during the transition from the state shown in  FIG.  18 A  to the state shown in  FIG.  18 B . In some other scenarios, as described below with reference to  FIG.  20   , the distal portion of needle ( 960 ) may deform during the transition from the state shown in  FIG.  18 A  to the state shown in  FIG.  18 B . In still other scenarios, both the sclera (S) and the distal portion of needle ( 960 ) may deform during the transition from the state shown in  FIG.  18 A  to the state shown in  FIG.  18 B . 
     With distal tip ( 962 ) located precisely at (or substantially at) the suprachoroidal space (SCS) as shown in  FIG.  17   , the operator may then advance plunger ( 986 ) distally relative to barrel ( 982 ), as shown in  FIG.  18 C . Such advancement of plunger ( 986 ) may drive fluid from barrel ( 982 ) through flexible conduit ( 970 ), and further through needle ( 960 ), such that the fluid ultimately exits distal tip ( 962 ) into the suprachoroidal space (SCS). 
     In the present example, since the needle axis (NA) is oriented at an angle (θ) that is not perpendicular to the suprachoroidal space (SCS), the fluid delivered via distal tip ( 962 ) may diffuse more easily within the suprachoroidal space (SCS) than the fluid might otherwise diffuse in a scenario where the fluid is delivered via a needle that is oriented perpendicular to the suprachoroidal space (SCS). In other words, the oblique angle (θ) of the needle axis (NA) may promote diffusion of the delivered fluid within the suprachoroidal space (SCS). The oblique angle (θ) of the needle axis (NA) may also reduce a risk of the choroid (C) being acutely stretched at the injection site, which might otherwise occur in scenarios where the fluid is delivered via a needle that is oriented perpendicular to the suprachoroidal space (SCS). Moreover, the oblique angle (θ) of the needle axis (NA) may reduce the risk of the retina (R) being undesirably penetrated by distal tip ( 962 ). 
     While instrument ( 900 ) is described above as being coupled with syringe ( 980 ) via conduit ( 970 ), instrument ( 900 ) may instead be coupled with any other suitable kind of fluid delivery device or system. For instance, instrument ( 900 ) may instead be coupled with an automated fluid delivery system. Instrument ( 900 ) may also incorporate any of the various other features described herein, including but not limited to the integral plunger ( 20 ) of instrument ( 10 ), actuator ( 250 ) of head ( 200 ) and associated components, adjustment member ( 470 ) of head ( 400 ), electrodes ( 504 ) of head ( 500 ) and associated components, and/or distal projections ( 830 ,  840 ) of head ( 800 ). 
     In the present example, distal tip ( 962 ) never penetrates the retina (R) and never reaches the vitreous chamber (V). Thus, distal tip ( 962 ) penetrates no further than the suprachoroidal space (SCS) or the choroid (Ch). In some other variations, at least a portion of distal tip ( 962 ) penetrates the retina (R). Moreover, distal tip ( 962 ) may reach the vitreous chamber (V) in some variations. 
     The configuration of instrument ( 900 ) as described above with reference to  FIGS.  16 - 17   , and the operation of instrument as described above with reference to  FIGS.  18 A- 18 C , may facilitate use of instrument ( 900 ) in eyes (E) having different sclera (S) thicknesses. In other words, instrument ( 900 ) may be just as suitable for use in an eye (E) having a thick sclera (S) as it is for use in an eye (E) having a thin sclera (S). This is illustrated in  FIGS.  19 - 20   . In particular,  FIG.  19    shows instrument ( 900 ) being used in an eye (E) having a relatively thin sclera (S). In such an eye (E), when instrument ( 900 ) is pivoted from the position shown in  FIG.  18 A  to the position shown in  FIG.  18 B , the resilience of needle ( 960 ) may overcome the resilience of the sclera (S), such that the distal end of needle ( 960 ) may cause some degree of deformation of the adjacent region of the sclera (S), without causing deformation of needle ( 960 ). Tip ( 962 ) of needle ( 960 ) may still reach, and remain in, the suprachoroidal space (SC S) to administer a therapeutic agent, etc., to the suprachoroidal space (SCS). As shown in  FIG.  19   , tip ( 962 ) does not traverse the choroid (Ch) during the procedure. In some cases, tip ( 962 ) does not even engage the choroid (Ch) during the procedure. 
       FIG.  20    shows instrument ( 900 ) being used in an eye (E) having a relatively thick sclera (S). In such an eye (E), when instrument ( 900 ) is pivoted from the position shown in  FIG.  18 A  to the position shown in  FIG.  18 B , the resilience of the sclera (S) may overcome the resilience of needle ( 960 ), such that the sclera (S) may cause the distal end of needle ( 960 ) to flexibly deform, without causing deformation of sclera (S). Tip ( 962 ) of needle ( 960 ) may still reach, and remain in, the suprachoroidal space (SCS) to administer a therapeutic agent, etc., to the suprachoroidal space (SCS). As shown in  FIG.  20   , tip ( 962 ) does not traverse the choroid (Ch) during the procedure. In some cases, tip ( 962 ) does not even engage the choroid (Ch) during the procedure. 
     While  FIG.  19    shows deformation of the sclera (S) without deformation of needle ( 960 ), and  FIG.  20    shows deformation of needle ( 960 ) without deformation of the sclera (S), there may be scenarios (e.g., where the sclera (S) has a thickness somewhere between the thickness shown in  FIG.  19    and the thickness shown in  FIG.  20   ) where the sclera (S) and needle ( 960 ) both deform to some degree. Again, regardless of whether the sclera (S) deforms, needle ( 960 ) deforms, or both the sclera (S) and needle ( 960 ) deform, tip ( 962 ) of needle ( 960 ) may still reach, and remain in, the suprachoroidal space (SCS) to administer a therapeutic agent, etc., to the suprachoroidal space (SCS). Moreover, regardless of whether the sclera (S) deforms, needle ( 960 ) deforms, or both the sclera (S) and needle ( 960 ) deform, tip ( 962 ) of needle ( 960 ) may avoid imparting undue trauma to the choroid (Ch). Thus, needle ( 960 ) may reach, and remain in, the suprachoroidal space (SCS) to administer a therapeutic agent, and avoid imparting undue trauma to the choroid (Ch), regardless of the thickness of the sclera (S). The length of needle ( 960 ) that is exposed relative to distal face ( 932 ), in combination with the oblique angle (θ) at which needle ( 960 ) enters the eye (E), in further combination with the resilient flexibility of needle ( 960 ) may further reduce the risk of tip ( 962 ) failing to reach the suprachoroidal space (SCS) (e.g., where tip ( 962 ) may otherwise fail to fully traverse the sclera (S)). 
     II. Examples of Combinations 
     The following examples relate to various non-exhaustive ways in which the teachings herein may be combined or applied. It should be understood that the following examples are not intended to restrict the coverage of any claims that may be presented at any time in this application or in subsequent filings of this application. No disclaimer is intended. The following examples are being provided for nothing more than merely illustrative purposes. It is contemplated that the various teachings herein may be arranged and applied in numerous other ways. It is also contemplated that some variations may omit certain features referred to in the below examples. Therefore, none of the aspects or features referred to below should be deemed critical unless otherwise explicitly indicated as such at a later date by the inventors or by a successor in interest to the inventors. If any claims are presented in this application or in subsequent filings related to this application that include additional features beyond those referred to below, those additional features shall not be presumed to have been added for any reason relating to patentability. 
     Example 1 
     An apparatus, comprising: (a) a body defining a fluid reservoir, the body having a distal end; and (b) a head at the distal end of the body, the head including: (i) a distal face, the distal face being configured to engage an exterior surface of a patient&#39;s eye at an anterior region of the patient&#39;s eye, (ii) a needle, the needle being configured to extend distally from the distal face, the needle having a length sufficient to extend through a sclera layer of the patient&#39;s eye and thereby position at least a portion of a distal tip of the needle in a suprachoroidal space of the patient&#39;s eye at an anterior region of the patient&#39;s eye, the needle being in fluid communication with the fluid reservoir such that the needle is operable to deliver fluid from the fluid reservoir into the suprachoroidal space of the patient&#39;s eye, and (iii) an indexing feature, the indexing feature being configured to complement a landmark of the patient&#39;s eye to thereby position the needle at a predetermined location in relation to the landmark of the patient&#39;s eye. 
     Example 2 
     The apparatus of Example 1, the distal face having a three-dimensional concave curvature such that the distal face is configured to complement a curvature of the patient&#39;s eye. 
     Example 3 
     The apparatus of any one or more of Examples 1 through 2, the distal face defining a longitudinal axis, the needle being configured to extend distally from the distal face along an exit axis that is obliquely oriented in relation to the longitudinal axis. 
     Example 4 
     The apparatus of Example 3, the exit axis being configured to define an exit angle with the longitudinal axis, the exit angle ranging from approximately 30 degrees to approximately 0 degrees. 
     Example 5 
     The apparatus of any one or more of Examples 1 through 4, further comprising a plunger slidably coupled with the body, the plunger being operable to drive fluid from the fluid reservoir out through the needle. 
     Example 6 
     The apparatus of any one or more of Examples 1 through 5, the distal face having three distal edges joined by corners. 
     Example 7 
     The apparatus of Example 6, at least one of the distal edges having a concave curvature. 
     Example 8 
     The apparatus of any one or more of Examples 6 through 7, the indexing feature being formed by at least one of the distal edges. 
     Example 9 
     The apparatus of any one or more of Examples 6 through 8, the corners being rounded. 
     Example 10 
     The apparatus of any one or more of Examples 1 through 9, the indexing feature including a distal edge of the distal face. 
     Example 11 
     The apparatus of any one or more of Examples 1 through 10, the indexing feature being configured to complement a limbus of the patient&#39;s eye. 
     Example 12 
     The apparatus of Example 11, the indexing feature having a curvature configured to complement a curvature of the limbus of the patient&#39;s eye. 
     Example 13 
     The apparatus of any one or more of Examples 1 through 12, the needle being longitudinally fixed relative to the distal face. 
     Example 14 
     The apparatus of any one or more of Examples 1 through 13, the needle extending along a curve. 
     Example 15 
     The apparatus of any one or more of Examples 1 through 14, the needle having a beveled distal tip, the beveled distal tip defining a bevel angle. 
     Example 16 
     The apparatus of Example 15, the bevel angle being configured to be parallel with boundaries of layers of the patient&#39;s eye as the needle is inserted into the patient&#39;s eye. 
     Example 17 
     The apparatus of any one or more of Examples 1 through 16, the needle being operable to translate relative to the distal face. 
     Example 18 
     The apparatus of Example 17, the needle being configured to translate between a proximal position and a distal position, the needle in the proximal position being positioned such that a distal tip of the needle is positioned proximally in relation to the distal face, the needle in the distal position being positioned such that a distal tip of the needle is positioned distally in relation to the distal face. 
     Example 19 
     The apparatus of any one or more of Examples 17 through 18, further comprising an actuator, the actuator being operable to drive translation of the needle relative to the distal face. 
     Example 20 
     The apparatus of Example 19, the actuator comprising a slider. 
     Example 21 
     The apparatus of any one or more of Examples 19 through 20, the actuator being positioned on the head. 
     Example 22 
     The apparatus of any one or more of Examples 1 through 21, further comprising a strain sensor, the strain sensor being operable to sense strain encountered by the needle as the needle penetrates the eye of the patient. 
     Example 23 
     The apparatus of Example 22, further comprising a response module, the response module being operable to provide a response based on a signal from the strain sensor. 
     Example 24 
     The apparatus of Example 23, the response module being configured to provide a response based on a signal from the strain sensor indicating that a distal tip of the needle has reached a suprachoroidal space in the eye of the patient. 
     Example 25 
     The apparatus of any one or more of Examples 23 through 24, the response module being configured to provide a response including one or more of tactile, visual, or audible feedback to an operator. 
     Example 26 
     The apparatus of any one or more of Examples 23 through 25, the response module being configured to provide a response including selectively permitting fluid communication from the fluid reservoir to the needle. 
     Example 27 
     The apparatus of Example 26, further comprising a valve interposed between the fluid reservoir and the needle, the response module being configured to selectively open the valve. 
     Example 28 
     The apparatus of any one or more of Examples 26 through 27, further comprising a pump operable to drive fluid from the fluid reservoir to the needle, the response module being configured to activate the pump. 
     Example 29 
     The apparatus of any one or more of Examples 1 through 28, the head defining a passageway containing at least a portion of the needle, a distal portion of the passageway defining a curve, the needle extending along the curve of the distal portion of the passageway. 
     Example 30 
     The apparatus of Example 29, the head further defining a longitudinal axis, the curve of the distal portion of the passageway orienting a distal portion of the needle along an exit axis that is obliquely oriented relative to the longitudinal axis of the head. 
     Example 31 
     The apparatus of any one or more of Examples 1 through 30, the needle including a distal portion that is resiliently biased to extend along a curve. 
     Example 32 
     The apparatus of Example 31, the needle being configured to translate between a proximal position and a distal position, the needle in the proximal position being positioned such that a distal tip of the needle is positioned proximally in relation to the distal face, the needle in the distal position being positioned such that a distal tip of the needle is positioned distally in relation to the distal face. 
     Example 33 
     The apparatus of Example 32, the head defining a passageway containing at least a portion of the needle, the needle being configured to translate along the passageway between the distal and proximal positions. 
     Example 34 
     The apparatus of Example 33, the passageway having a straight configuration, the passageway being configured to deform the distal portion of the needle into a straight configuration when the needle is in the proximal position. 
     Example 35 
     The apparatus of Example 34, the resilient bias of the distal portion of the needle being configured to urge the distal portion of the needle along a curve as the distal portion is exposed relative to the distal face during movement of the needle from the proximal position to the distal position. 
     Example 36 
     The apparatus of any one or more of Examples 1 through 35, further comprising an adjustment member, the head defining a longitudinal axis, the adjustment member being operable to adjust a needle exit axis in relation to the longitudinal axis to thereby adjust an oblique needle exit angle defined between the longitudinal axis and the needle exit axis. 
     Example 37 
     The apparatus of Example 36, the adjustment member being integrated into the head. 
     Example 38 
     The apparatus of any one or more of Examples 36 through 37, the adjustment member including a wheel, the wheel being rotatable to adjust the needle exit angle. 
     Example 39 
     The apparatus of Example 38, the adjustment member further comprising an axle defining a rotation axis, the wheel being rotatable about the rotation axis. 
     Example 40 
     The apparatus of Example 39, the wheel defining a needle passageway, the needle extending along the needle passageway. 
     Example 41 
     The apparatus of Example 40, the needle passageway being positioned such that the rotation axis passes through the needle passageway. 
     Example 42 
     The apparatus of any one or more of Examples 36 through 41, the adjustment member including indicia, the indicia being configured to provide visual feedback indicating the needle exit angle. 
     Example 43 
     The apparatus of any one or more of Examples 1 through 42, further comprising electrodes and a processing module, the electrodes being configured to contact tissue, the processing module being configured to detect a position of the needle in the patient&#39;s eye based on signals from the electrodes. 
     Example 44 
     The apparatus of Example 43, the processing module being configured to detect a position of the needle in the patient&#39;s eye based on an electrical potential picked up by the electrodes. 
     Example 45 
     The apparatus of any one or more of Examples 43 through 44, the electrodes including at least one electrode on the head, the at least one electrode on the head being configured to operate at a first polarity. 
     Example 46 
     The apparatus of Example 45, the needle forming another one of the electrodes, the needle being configured to operate at a second polarity. 
     Example 47 
     The apparatus of any one or more of Examples 1 through 46, the head further including at least one distal projection, the at least one distal projection being laterally offset from the needle, the distal face being proximally offset from the distal projection such that the distal projection and the distal face are configured to define a gap, the needle being configured to extend through the gap. 
     Example 48 
     The apparatus of Example 47, the at least one distal projection comprising a plurality of distal projections positioned in an angularly spaced apart array about the needle. 
     Example 49 
     The apparatus of any one or more of Examples 47 through 48, the at least one distal projection comprising a distal projection that continuously spans a full circumference about the needle. 
     Example 50 
     The apparatus of any one or more of Examples 47 through 49, the at least one distal projection being configured to engage the eye at one or more corresponding positions that are laterally spaced away from a location where the needle penetrates the eye, such that the at least one distal projection is configured to maintain tension in a sclera layer of the eye in the location where the needle penetrates the eye. 
     Example 51 
     An apparatus, comprising: (a) a body defining a fluid reservoir, the body having a distal end; and (b) a head at the distal end of the body, the head including: (i) a distal face, the distal face being configured to engage an exterior surface of a patient&#39;s eye at an anterior region of the patient&#39;s eye, the distal face having a three-dimensional concave curvature such that the distal face is configured to complement a curvature of the patient&#39;s eye, and (ii) a needle, the needle being configured to extend distally from the distal face, the needle having a length sufficient to extend through a sclera layer of the patient&#39;s eye and thereby position at least a portion of a distal tip of the needle in a suprachoroidal space of the patient&#39;s eye at an anterior region of the patient&#39;s eye, the needle being in fluid communication with the fluid reservoir such that the needle is operable to deliver fluid from the fluid reservoir into the suprachoroidal space of the patient&#39;s eye. 
     Example 52 
     The apparatus of Example 51, further comprising an indexing feature, the indexing feature being configured to complement a landmark of the patient&#39;s eye to thereby position the needle at a predetermined location in relation to the landmark of the patient&#39;s eye. 
     Example 53 
     The apparatus of Example 52, the distal face having three distal edges joined by corners. 
     Example 54 
     The apparatus of Example 53, at least one of the distal edges having a concave curvature. 
     Example 55 
     The apparatus of any one or more of Examples 53 through 54, the indexing feature being formed by at least one of the distal edges. 
     Example 56 
     The apparatus of any one or more of Examples 52 through 55, the indexing feature including a distal edge of the distal face. 
     Example 57 
     The apparatus of any one or more of Examples 52 through 56, the indexing feature being configured to complement a limbus of the patient&#39;s eye. 
     Example 58 
     The apparatus of Example 57, the indexing feature having a curvature configured to complement a curvature of the limbus of the patient&#39;s eye. 
     Example 59 
     The apparatus of any one or more of Examples 51 through 58, the distal face defining a longitudinal axis, the needle being configured to extend distally from the distal face along an exit axis that is obliquely oriented in relation to the longitudinal axis. 
     Example 60 
     The apparatus of Example 59, the exit axis being configured to define an exit angle with the longitudinal axis, the exit angle ranging from approximately 30 degrees to approximately 0 degrees. 
     Example 61 
     The apparatus of any one or more of Examples 51 through 60, further comprising a plunger slidably coupled with the body, the plunger being operable to drive fluid from the fluid reservoir out through the needle. 
     Example 62 
     The apparatus of any one or more of Examples 51 through 61, the distal face having three distal edges joined by corners. 
     Example 63 
     The apparatus of Example 62, at least one of the distal edges having a concave curvature. 
     Example 64 
     The apparatus of any one or more of Examples 62 through 63, the corners being rounded. 
     Example 65 
     The apparatus of any one or more of Examples 51 through 64, the needle being longitudinally fixed relative to the distal face. 
     Example 66 
     The apparatus of any one or more of Examples 51 through 65, the needle extending along a curve. 
     Example 67 
     The apparatus of any one or more of Examples 51 through 66, the needle having a beveled distal tip, the beveled distal tip defining a bevel angle. 
     Example 68 
     The apparatus of Example 67, the bevel angle being configured to be parallel with boundaries of layers of the patient&#39;s eye as the needle is inserted into the patient&#39;s eye. 
     Example 69 
     The apparatus of any one or more of Examples 51 through 68, the needle being operable to translate relative to the distal face. 
     Example 70 
     The apparatus of Example 69, the needle being configured to translate between a proximal position and a distal position, the needle in the proximal position being positioned such that a distal tip of the needle is positioned proximally in relation to the distal face, the needle in the distal position being positioned such that a distal tip of the needle is positioned distally in relation to the distal face. 
     Example 71 
     The apparatus of any one or more of Examples 69 through 70, further comprising an actuator, the actuator being operable to drive translation of the needle relative to the distal face. 
     Example 72 
     The apparatus of Example 71, the actuator comprising a slider. 
     Example 73 
     The apparatus of any one or more of Examples 71 through 72, the actuator being positioned on the head. 
     Example 74 
     The apparatus of any one or more of Examples 51 through 73, further comprising a strain sensor, the strain sensor being operable to sense strain encountered by the needle as the needle penetrates the eye of the patient. 
     Example 75 
     The apparatus of Example 74, further comprising a response module, the response module being operable to provide a response based on a signal from the strain sensor. 
     Example 76 
     The apparatus of Example 75, the response module being configured to provide a response based on a signal from the strain sensor indicating that a distal tip of the needle has reached a suprachoroidal space in the eye of the patient. 
     Example 77 
     The apparatus of any one or more of Examples 75 through 76, the response module being configured to provide a response including one or more of tactile, visual, or audible feedback to an operator. 
     Example 78 
     The apparatus of any one or more of Examples 75 through 77, the response module being configured to provide a response including selectively permitting fluid communication from the fluid reservoir to the needle. 
     Example 79 
     The apparatus of Example 78, further comprising a valve interposed between the fluid reservoir and the needle, the response module being configured to selectively open the valve. 
     Example 80 
     The apparatus of any one or more of Examples 78 through 79, further comprising a pump operable to drive fluid from the fluid reservoir to the needle, the response module being configured to activate the pump. 
     Example 81 
     The apparatus of any one or more of Examples 51 through 80, the head defining a passageway containing at least a portion of the needle, a distal portion of the passageway defining a curve, the needle extending along the curve of the distal portion of the passageway. 
     Example 82 
     The apparatus of Example 81, the head further defining a longitudinal axis, the curve of the distal portion of the passageway orienting a distal portion of the needle along an exit axis that is obliquely oriented relative to the longitudinal axis of the head. 
     Example 83 
     The apparatus of any one or more of Examples 51 through 82, the needle including a distal portion that is resiliently biased to extend along a curve. 
     Example 84 
     The apparatus of Example 83, the needle being configured to translate between a proximal position and a distal position, the needle in the proximal position being positioned such that a distal tip of the needle is positioned proximally in relation to the distal face, the needle in the distal position being positioned such that a distal tip of the needle is positioned distally in relation to the distal face. 
     Example 85 
     The apparatus of Example 84, the head defining a passageway containing at least a portion of the needle, the needle being configured to translate along the passageway between the distal and proximal positions. 
     Example 86 
     The apparatus of Example 85, the passageway having a straight configuration, the passageway being configured to deform the distal portion of the needle into a straight configuration when the needle is in the proximal position. 
     Example 87 
     The apparatus of Example 86, the resilient bias of the distal portion of the needle being configured to urge the distal portion of the needle along a curve as the distal portion is exposed relative to the distal face during movement of the needle from the proximal position to the distal position. 
     Example 88 
     The apparatus of any one or more of Examples 51 through 87, further comprising an adjustment member, the head defining a longitudinal axis, the adjustment member being operable to adjust a needle exit axis in relation to the longitudinal axis to thereby adjust an oblique needle exit angle defined between the longitudinal axis and the needle exit axis. 
     Example 89 
     The apparatus of Example 88, the adjustment member being integrated into the head. 
     Example 90 
     The apparatus of any one or more of Examples 88 through 89, the adjustment member including a wheel, the wheel being rotatable to adjust the needle exit angle. 
     Example 91 
     The apparatus of Example 90, the adjustment member further comprising an axle defining a rotation axis, the wheel being rotatable about the rotation axis. 
     Example 92 
     The apparatus of Example 91, the wheel defining a needle passageway, the needle extending along the needle passageway. 
     Example 93 
     The apparatus of Example 92, the needle passageway being positioned such that the rotation axis passes through the needle passageway. 
     Example 94 
     The apparatus of any one or more of Examples 88 through 93, the adjustment member including indicia, the indicia being configured to provide visual feedback indicating the needle exit angle. 
     Example 95 
     The apparatus of any one or more of Examples 51 through 94, further comprising electrodes and a processing module, the electrodes being configured to contact tissue, the processing module being configured to detect a position of the needle in the patient&#39;s eye based on signals from the electrodes. 
     Example 96 
     The apparatus of Example 95, the processing module being configured to detect a position of the needle in the patient&#39;s eye based on an electrical potential picked up by the electrodes. 
     Example 97 
     The apparatus of any one or more of Examples 95 through 96, the electrodes including at least one electrode on the head, the at least one electrode on the head being configured to operate at a first polarity. 
     Example 98 
     The apparatus of Example 97, the needle forming another one of the electrodes, the needle being configured to operate at a second polarity. 
     Example 99 
     The apparatus of any one or more of Examples 51 through 98, the head further including at least one distal projection, the at least one distal projection being laterally offset from the needle, the distal face being proximally offset from the distal projection such that the distal projection and the distal face are configured to define a gap, the needle being configured to extend through the gap. 
     Example 100 
     The apparatus of Example 99, the at least one distal projection comprising a plurality of distal projections positioned in an angularly spaced apart array about the needle. 
     Example 101 
     The apparatus of any one or more of Examples 99 through 100, the at least one distal projection comprising a distal projection that continuously spans a full circumference about the needle. 
     Example 102 
     The apparatus of any one or more of Examples 99 through 101, the at least one distal projection being configured to engage the eye at one or more corresponding positions that are laterally spaced away from a location where the needle penetrates the eye, such that the at least one distal projection is configured to maintain tension in a sclera layer of the eye in the location where the needle penetrates the eye. 
     Example 103 
     An apparatus, comprising: (a) a body defining a fluid reservoir, the body having a distal end; and (b) a head at the distal end of the body, the head including: (i) a distal face, the distal face being configured to engage an exterior surface of a patient&#39;s eye at an anterior region of the patient&#39;s eye, the distal face defining a longitudinal axis, and (ii) a needle, the needle being configured to extend distally from the distal face along an exit axis that is obliquely oriented in relation to the longitudinal axis, the needle having a length sufficient to extend through a sclera layer of the patient&#39;s eye and thereby position at least a portion of a distal tip of the needle in a suprachoroidal space of the patient&#39;s eye at an anterior region of the patient&#39;s eye, the needle being in fluid communication with the fluid reservoir such that the needle is operable to deliver fluid from the fluid reservoir into the suprachoroidal space of the patient&#39;s eye. 
     Example 104 
     The apparatus of Example 103, further comprising an indexing feature, the indexing feature being configured to complement a landmark of the patient&#39;s eye to thereby position the needle at a predetermined location in relation to the landmark of the patient&#39;s eye. 
     Example 105 
     The apparatus of Example 104, the distal face having three distal edges joined by corners. 
     Example 106 
     The apparatus of Example 105, at least one of the distal edges having a concave curvature. 
     Example 107 
     The apparatus of any one or more of Examples 105 through 106, the indexing feature being formed by at least one of the distal edges. 
     Example 108 
     The apparatus of any one or more of Examples 104 through 107, the indexing feature including a distal edge of the distal face. 
     Example 109 
     The apparatus of any one or more of Examples 104 through 108, the indexing feature being configured to complement a limbus of the patient&#39;s eye. 
     Example 110 
     The apparatus of Example 109, the indexing feature having a curvature configured to complement a curvature of the limbus of the patient&#39;s eye. 
     Example 111 
     The apparatus of any one or more of Examples 103 through 110, the exit axis being configured to define an exit angle with the longitudinal axis, the exit angle ranging from approximately 30 degrees to approximately 0 degrees. 
     Example 112 
     The apparatus of any one or more of Examples 103 through 111, further comprising a plunger slidably coupled with the body, the plunger being operable to drive fluid from the fluid reservoir out through the needle. 
     Example 113 
     The apparatus of any one or more of Examples 103 through 112, the distal face having three distal edges joined by corners. 
     Example 114 
     The apparatus of Example 113, at least one of the distal edges having a concave curvature. 
     Example 115 
     The apparatus of any one or more of Examples 113 through 114, the corners being rounded. 
     Example 116 
     The apparatus of any one or more of Examples 103 through 115, the needle being longitudinally fixed relative to the distal face. 
     Example 117 
     The apparatus of any one or more of Examples 103 through 116, the needle extending along a curve. 
     Example 118 
     The apparatus of any one or more of Examples 103 through 117, the needle having a beveled distal tip, the beveled distal tip defining a bevel angle. 
     Example 119 
     The apparatus of Example 118, the bevel angle being configured to be parallel with boundaries of layers of the patient&#39;s eye as the needle is inserted into the patient&#39;s eye. 
     Example 120 
     The apparatus of any one or more of Examples 103 through 119, the needle being operable to translate relative to the distal face. 
     Example 121 
     The apparatus of Example 120, the needle being configured to translate between a proximal position and a distal position, the needle in the proximal position being positioned such that a distal tip of the needle is positioned proximally in relation to the distal face, the needle in the distal position being positioned such that a distal tip of the needle is positioned distally in relation to the distal face. 
     Example 122 
     The apparatus of any one or more of Examples 120 through 121, further comprising an actuator, the actuator being operable to drive translation of the needle relative to the distal face. 
     Example 123 
     The apparatus of Example 122, the actuator comprising a slider. 
     Example 124 
     The apparatus of any one or more of Examples 122 through 123, the actuator being positioned on the head. 
     Example 125 
     The apparatus of any one or more of Examples 103 through 124, further comprising a strain sensor, the strain sensor being operable to sense strain encountered by the needle as the needle penetrates the eye of the patient. 
     Example 126 
     The apparatus of Example 125, further comprising a response module, the response module being operable to provide a response based on a signal from the strain sensor. 
     Example 127 
     The apparatus of Example 126, the response module being configured to provide a response based on a signal from the strain sensor indicating that a distal tip of the needle has reached a suprachoroidal space in the eye of the patient. 
     Example 128 
     The apparatus of any one or more of Examples 126 through 127, the response module being configured to provide a response including one or more of tactile, visual, or audible feedback to an operator. 
     Example 129 
     The apparatus of any one or more of Examples 126 through 128, the response module being configured to provide a response including selectively permitting fluid communication from the fluid reservoir to the needle. 
     Example 130 
     The apparatus of Example 129, further comprising a valve interposed between the fluid reservoir and the needle, the response module being configured to selectively open the valve. 
     Example 131 
     The apparatus of any one or more of Examples 129 through 130, further comprising a pump operable to drive fluid from the fluid reservoir to the needle, the response module being configured to activate the pump. 
     Example 132 
     The apparatus of any one or more of Examples 103 through 131, the head defining a passageway containing at least a portion of the needle, a distal portion of the passageway defining a curve, the needle extending along the curve of the distal portion of the passageway. 
     Example 133 
     The apparatus of Example 132, the head further defining a longitudinal axis, the curve of the distal portion of the passageway orienting a distal portion of the needle along the exit axis that is obliquely oriented relative to the longitudinal axis of the head. 
     Example 134 
     The apparatus of any one or more of Examples 103 through 133, the needle including a distal portion that is resiliently biased to extend along a curve. 
     Example 135 
     The apparatus of Example 134, the needle being configured to translate between a proximal position and a distal position, the needle in the proximal position being positioned such that a distal tip of the needle is positioned proximally in relation to the distal face, the needle in the distal position being positioned such that a distal tip of the needle is positioned distally in relation to the distal face. 
     Example 136 
     The apparatus of Example 135, the head defining a passageway containing at least a portion of the needle, the needle being configured to translate along the passageway between the distal and proximal positions. 
     Example 137 
     The apparatus of Example 136, the passageway having a straight configuration, the passageway being configured to deform the distal portion of the needle into a straight configuration when the needle is in the proximal position. 
     Example 138 
     The apparatus of Example 137, the resilient bias of the distal portion of the needle being configured to urge the distal portion of the needle along a curve as the distal portion is exposed relative to the distal face during movement of the needle from the proximal position to the distal position. 
     Example 139 
     The apparatus of any one or more of Examples 103 through 138, further comprising an adjustment member, the head defining a longitudinal axis, the adjustment member being operable to adjust a needle exit axis in relation to the longitudinal axis to thereby adjust an oblique needle exit angle defined between the longitudinal axis and the needle exit axis. 
     Example 140 
     The apparatus of Example 139, the adjustment member being integrated into the head. 
     Example 141 
     The apparatus of any one or more of Examples 139 through 140, the adjustment member including a wheel, the wheel being rotatable to adjust the needle exit angle. 
     Example 142 
     The apparatus of Example 141, the adjustment member further comprising an axle defining a rotation axis, the wheel being rotatable about the rotation axis. 
     Example 143 
     The apparatus of Example 142, the wheel defining a needle passageway, the needle extending along the needle passageway. 
     Example 144 
     The apparatus of Example 143, the needle passageway being positioned such that the rotation axis passes through the needle passageway. 
     Example 145 
     The apparatus of any one or more of Examples 139 through 144, the adjustment member including indicia, the indicia being configured to provide visual feedback indicating the needle exit angle. 
     Example 146 
     The apparatus of any one or more of Examples 103 through 145, further comprising electrodes and a processing module, the electrodes being configured to contact tissue, the processing module being configured to detect a position of the needle in the patient&#39;s eye based on signals from the electrodes. 
     Example 147 
     The apparatus of Example 146, the processing module being configured to detect a position of the needle in the patient&#39;s eye based on an electrical potential picked up by the electrodes. 
     Example 148 
     The apparatus of any one or more of Examples 146 through 147, the electrodes including at least one electrode on the head, the at least one electrode on the head being configured to operate at a first polarity. 
     Example 149 
     The apparatus of Example 148, the needle forming another one of the electrodes, the needle being configured to operate at a second polarity. 
     Example 150 
     The apparatus of any one or more of Examples 103 through 149, the head further including at least one distal projection, the at least one distal projection being laterally offset from the needle, the distal face being proximally offset from the distal projection such that the distal projection and the distal face are configured to define a gap, the needle being configured to extend through the gap. 
     Example 151 
     The apparatus of Example 150, the at least one distal projection comprising a plurality of distal projections positioned in an angularly spaced apart array about the needle. 
     Example 152 
     The apparatus of any one or more of Examples 150 through 151, the at least one distal projection comprising a distal projection that continuously spans a full circumference about the needle. 
     Example 153 
     The apparatus of any one or more of Examples 150 through 152, the at least one distal projection being configured to engage the eye at one or more corresponding positions that are laterally spaced away from a location where the needle penetrates the eye, such that the at least one distal projection is configured to maintain tension in a sclera layer of the eye in the location where the needle penetrates the eye. 
     Example 154 
     The apparatus of any one or more of Examples 103 through 153, the distal face having a three-dimensional concave curvature such that the distal face is configured to complement a curvature of the patient&#39;s eye. 
     Example 155 
     An apparatus, comprising: (a) a shaft having: (i) a proximal end, (ii) a distal end, and (iii) a fluid pathway; and (b) a head at the distal end of the shaft, the head including: (i) a distal face, the distal face being configured to engage an exterior surface of a patient&#39;s eye at an anterior region of the patient&#39;s eye, the distal face having a concave curvature contoured to complement a curvature of the patient&#39;s eye, and (ii) a needle, the needle being configured to extend distally from the distal face, the needle having a length sufficient to extend through a sclera layer of the patient&#39;s eye and thereby position at least a portion of a distal tip of the needle in a suprachoroidal space of the patient&#39;s eye at an anterior region of the patient&#39;s eye while the distal face is seated against the patient&#39;s eye, the needle being in fluid communication with the fluid pathway such that the needle is operable to deliver fluid from the fluid pathway into the suprachoroidal space of the patient&#39;s eye. 
     Example 156 
     The apparatus of Example 155, the head further including an indexing feature, the indexing feature being configured to complement a landmark of the patient&#39;s eye to thereby position the needle at a predetermined location in relation to the landmark of the patient&#39;s eye. 
     Example 157 
     The apparatus of Example 156, the distal face having an edge, the edge defining the indexing feature. 
     Example 158 
     The apparatus of any of Examples 156 through 157, the indexing feature being configured to complement a limbus of the patient&#39;s eye. 
     Example 159 
     The apparatus of Example 158, the indexing feature having a curvature configured to complement a curvature of the limbus of the patient&#39;s eye. 
     Example 160 
     The apparatus of any of Examples 155 through 159, the needle being longitudinally fixed relative to the distal face. 
     Example 161 
     The apparatus of any of Examples 155 through 160, the distal face having a three-dimensional concave curvature. 
     Example 162 
     The apparatus of any of Examples 155 through 161, the shaft defining a longitudinal axis, the distal face being oriented transversely relative to the longitudinal axis. 
     Example 163 
     The apparatus of any of Examples 155 through 162, the shaft defining a longitudinal axis, the needle extending along an exit axis that is parallel with the longitudinal axis of the shaft. 
     Example 164 
     The apparatus of any of Examples 155 through 163, the needle having a straight configuration. 
     Example 165 
     The apparatus of any of Examples 155 through 164, the needle having a beveled distal tip, the beveled distal tip defining a bevel angle. 
     Example 166 
     The apparatus of Example 165, the bevel angle being configured to be parallel with boundaries of layers of the patient&#39;s eye as the needle is inserted into the patient&#39;s eye. 
     Example 167 
     The apparatus of any of Examples 155 through 166, the fluid pathway comprising a flexible conduit. 
     Example 168 
     The apparatus of Example 167, further comprising a syringe coupled with the flexible conduit. 
     Example 169 
     The apparatus of Example 168, the syringe being spaced apart from the shaft via the flexible conduit. 
     Example 170 
     The apparatus of any of Examples 155 through 169, the shaft further including a laterally facing guidance feature, the laterally facing guidance feature being configured to complement a landmark of the patient&#39;s eye to thereby position the needle at a predetermined orientation in relation to the patient&#39;s eye. 
     Example 171 
     The apparatus of Example 170, the laterally facing guidance feature including a concave face configured to complement the curvature of the landmark of the patient&#39;s eye. 
     Example 172 
     The apparatus of Example 171, the landmark including a limbus of the patient&#39;s eye. 
     Example 173 
     The apparatus of any of Examples 155 through 172, the shaft further including a marking assembly, the marking assembly being configured to mark a needle entry point in relation to a landmark of the patient&#39;s eye. 
     Example 174 
     The apparatus of Example 173, the marking assembly being positioned at the proximal end of the shaft. 
     Example 175 
     The apparatus of any of Examples 173 through 174, the marking assembly including two prongs fixedly spaced apart from each other by a predetermined distance. 
     Example 176 
     The apparatus of Example 175, each prong of the two prongs having an atraumatic configuration. 
     Example 177 
     The apparatus of any of Examples 173 through 176, the marking assembly being configured to mark a needle entry point in relation to a limbus of the patient&#39;s eye. 
     III. Miscellaneous 
     To the extent that several examples herein are described in the context of a cannula guide being positioned near an already-formed scleral incision ( 23 ), it should be understood that other kinds of procedures may be employed. For instance, in some variations of the procedures described herein, the cannula guide may be secured to the eye ( 20 ) first; and then the scleral incision ( 23 ) may be formed after the cannula guide has been secured to the eye ( 20 ). Other suitable steps and sequences that may be carried out in procedures that include a combination of a scleral incision ( 23 ) and a cannula guide will be apparent to those skilled in the art in view of the teachings herein. 
     It should be understood that any of the versions of the instruments described herein may include various other features in addition to or in lieu of those described above. By way of example only, any of the devices herein may also include one or more of the various features disclosed in any of the various references that are incorporated by reference herein. 
     It should be understood that any one or more of the teachings, expressions, embodiments, examples, etc. described herein may be combined with any one or more of the other teachings, expressions, embodiments, examples, etc. that are described herein. The above-described teachings, expressions, embodiments, examples, etc. should therefore not be viewed in isolation relative to each other. Various suitable ways in which the teachings herein may be combined will be readily apparent to those skilled in the art in view of the teachings herein. Such modifications and variations are intended to be included within the scope of the claims. 
     It should be appreciated that any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material. 
     Versions described above may be designed to be disposed of after a single use, or they can be designed to be used multiple times. Versions may, in either or both cases, be reconditioned for reuse after at least one use. Reconditioning may include any combination of the steps of disassembly of the device, followed by cleaning or replacement of particular pieces, and subsequent reassembly. In particular, some versions of the device may be disassembled, and any number of the particular pieces or parts of the device may be selectively replaced or removed in any combination. Upon cleaning and/or replacement of particular parts, some versions of the device may be reassembled for subsequent use either at a reconditioning facility, or by an operator immediately prior to a procedure. Those skilled in the art will appreciate that reconditioning of a device may utilize a variety of techniques for disassembly, cleaning/replacement, and reassembly. Use of such techniques, and the resulting reconditioned device, are all within the scope of the present application. 
     By way of example only, versions described herein may be sterilized before and/or after a procedure. In one sterilization technique, the device is placed in a closed and sealed container, such as a plastic or TYVEK bag. The container and device may then be placed in a field of radiation that can penetrate the container, such as gamma radiation, x-rays, or high-energy electrons. The radiation may kill bacteria on the device and in the container. The sterilized device may then be stored in the sterile container for later use. A device may also be sterilized using any other technique known in the art, including but not limited to beta or gamma radiation, ethylene oxide, or steam. 
     Having shown and described various embodiments of the present invention, further adaptations of the methods and systems described herein may be accomplished by appropriate modifications by one of ordinary skill in the art without departing from the scope of the present invention. Several of such potential modifications have been mentioned, and others will be apparent to those skilled in the art. For instance, the examples, embodiments, geometrics, materials, dimensions, ratios, steps, and the like discussed above are illustrative and are not required. Accordingly, the scope of the present invention should be considered in terms of the following claims and is understood not to be limited to the details of structure and operation shown and described in the specification and drawings.