Patent Publication Number: US-2018042768-A1

Title: Subretinal fluid drainage instruments, systems, and methods

Description:
TECHNICAL FIELD 
     The present disclosure is directed to instruments, systems, and methods for draining fluid from behind a retinal membrane of an eye. 
     BACKGROUND 
     Under normal conditions in the human eye, the retina is physically attached to the choroid. Vitreous humor, a transparent jellylike material, fills the posterior segment of the eye and also helps secure the retina against the choroid. 
     Some ophthalmic conditions are characterized by detachment of the retina from the retinal pigment epithelium (RPE) and choroid. This typically happens when there is a tear in the retina. Retinal tears may allow vitreous humor or aqueous humor to flow between the retina and the RPE/choroid, resulting in an undesirable buildup of subretinal fluid. This may detach a portion of the retina from the choroid. However, when the retina detaches from the RPE/choroid, the detached portion of the retina is no longer able to receive nourishment from the choroid, which may cause the detached portions of the retina to be permanently damaged, resulting in loss of vision. 
     Repairing these conditions typically requires a surgical intervention. A surgeon may insert a probe or other instrument into the posterior segment of the eye via a sclerotomy, an incision through the sclera at the pars plana. While viewing the posterior segment under a microscope, the surgeon may cut and aspirate vitreous using a vitrectomy probe in order to gain access to the retinal detachment or tear. The surgeon may manipulate and flatten the detached or torn portion of the retina against the RPE/choroid in its proper location. An additional fluid, such as a gas or a silicone oil can be injected into the eye to serve as a retinal tamponade fluid to maintain the detached portion of the retina against the RPE/choroid. 
     The surgeon then typically drains any subretinal fluid present between the retina and the choroid through a retinal break or a purpose-made retinotomy and then initiates fluid air exchange while continuing drainage of subretinal fluid. After the detached or torn portion of the retina is properly located and the subretinal fluid is drained, the surgeon may take additional steps to secure the retina in place typically by applying laser energy to the retinal defects. 
     SUMMARY 
     The present disclosure is directed to instruments, systems, and methods of removing unwanted material from subretinal space in the eye. 
     Exemplary medical instruments and systems are provided herein. An exemplary surgical instrument for removal of subretinal fluid may include a handle coupleable to an aspiration pressure source. The handle may have a rotational structure rotatable around an axis of a handle body when manipulated by a user. The surgical instrument may include a first elongate tubular member having a first proximal end and a first distal end and may include a second elongate tubular member having a second proximal end and a second distal end. The first proximal end of the first elongate tubular member may be coupled to the rotational structure such that the first elongate tubular member is rotatable around the axis of the handle body. The second proximal end of the second elongate tubular member may be coupled to the first distal end of the first elongate tubular member and may be curved when exposed to body temperature. The surgical instrument may further include a port formed through a wall of the second elongate tubular member for aspirating material from a body cavity through the first and second elongate tubular members. 
     Another exemplary surgical instrument may include a handle that may be coupled to a conduit. The handle may have a rotational structure rotatable around an axis of a handle body of the handle. The surgical instrument may further include a first elongate tubular member having a first proximal end; a first distal end; and a first lumen extending through the first elongate tubular member. The first proximal end may be coupled to the rotational structure such that the first elongate tubular member is rotatable around the axis. A second elongate tubular member may also be included in the surgical instrument and may have a second proximal end; a second distal end; and a second lumen extending through the second elongate tubular member. The first lumen may be in fluid communication with the second lumen. The second proximal end of the second elongate tubular member may be coupled to the first distal end of the first elongate tubular member. The second distal end may be a rounded, closed distal tip. The surgical instrument may also include a port formed on one side of the second elongate tubular member and through a wall of the second elongate tubular member. The port may be operable to aspirate material from a body cavity through the first lumen and the second lumen. The body cavity may be a subretinal space. 
     An exemplary ophthalmic surgical system may include an aspiration pressure source coupled to a conduit and a surgical handpiece coupled to the aspiration pressure source by the conduit. The surgical handpiece may include a handle body coupled to the conduit. The handle body may have a rotational structure rotatable around an axis of the handle body. The surgical handpiece may further include a first elongate tubular member having a first proximal end; a first distal end; and a first lumen extending through the first elongate tubular member. The surgical handpiece may also include a second elongate tubular member having a second proximal end; a second distal end forming a closed distal tip; and a second lumen extending through the second elongate tubular member and in fluid communication with the first lumen. The first proximal end may be coupled to the rotational structure such that the first elongate tubular member is rotatable around the axis, and the second proximal end of the second elongate tubular member may be coupled to the first distal end of the first elongate tubular member. The second elongate tubular member may be more flexible than the first elongate tubular member. The surgical handpiece may also include a port formed through a wall of the second elongate tubular member for aspirating material from a body cavity through the first lumen and the second lumen. 
     Exemplary methods of cleaning a tissue surface are provided. An exemplary method may include introducing a surgical instrument, such as an implementation of the exemplary surgical instruments described herein, into the eye of a patient. A distal region of the instrument may be positioned into subretinal space by a user. An aspiration pressure source may be activated to cause fluid to exit the subretinal space. A distal region of the instrument may be rotated by user manipulation of a rotational structure on a handle body of the instrument. A portion of the instrument outside the eye may be manipulated so that a second elongate tubular member of the instrument travels along the retina while the pressure gradient is used to aspirate material from the eye. As a result, the port of the second elongate tubular member travels along the retinal surface while the pressure gradient is used to aspirate material from the eye. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory in nature and are intended to provide an understanding of the present disclosure without limiting the scope of the present disclosure. In that regard, additional aspects, features, and advantages of the present disclosure will be apparent to one skilled in the art from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate implementations of the instruments, systems, and methods disclosed herein and together with the description, serve to explain the principles of the present disclosure. 
         FIG. 1  illustrates a perspective view of an exemplary surgical system. 
         FIG. 2  is an illustration of an exemplary block diagram of the exemplary surgical system of  FIG. 1 . 
         FIG. 3  is an illustration of an exemplary surgical instrument in situ in an eye. 
         FIGS. 4A and 4B  illustrate the exemplary surgical instrument of  FIG. 3  in two different states. 
         FIGS. 5A and 5B  illustrate rotational capabilities of the exemplary surgical instrument of  FIG. 3 . 
         FIG. 6  is a flowchart of an example method for using the surgical instrument of  FIG. 3  to clean the surface of a membrane. 
         FIG. 7  shows a distal end of an elongate tubular member of the example surgical instrument of  FIG. 3  oriented relative to an eye and, particularly, to the retina of the eye. 
     
    
    
     The accompanying drawings may be better understood by reference to the following detailed description. 
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the implementations illustrated in the drawings. Specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is intended. Any alterations and further modifications to the described instruments, systems, methods, and any further application of the principles of the present disclosure are fully contemplated as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one implementation may be combined with the features, components, and/or steps described with respect to other implementations of the present disclosure. For example, although explanatory references are made to ophthalmic applications, other medical applications are included within the scope of the present disclosure. For simplicity, in some instances the same reference numbers are used throughout the drawings to refer to the same or like parts. 
     The present disclosure is directed to instruments, systems, and methods for removing subretinal fluid in order to reattach a torn or detached retina. The instruments and systems may include instruments having specially formed distal regions. In some examples, the distal region may be curved in a manner corresponding to the curvature of the eye. Some distal region implementations may include a side port on a single side of the distal region. Having the port, or in some implementations multiple ports, on a single side may prevent incarceration of the retina or other tissues and may simplify use of the instruments. A pressure gradient may cause the subretinal fluid to flow into the single side port for removal from the eye. Depending on the implementation, the pressure gradient may be naturally occurring, such as when pressure present in the eye (e.g., the intraocular pressure) is greater than pressure present within the instrument, thereby causing subretinal fluid to move toward the lower pressure, out of the eye. In additional implementations, the pressure gradient may be artificially induced by any aspiration pressure source, such as a pump, a vacuum, or other pressure gradient inducing device. 
     The single-side port of the disclosed instruments may permit the distal region to rotate within the eye while minimizing the chance of incarcerating the retina within the instrument. In contrast, when multiple ports are provided on an instrument, such as two ports that are laterally opposite each other, the instrument can grasp the retina and retinal pigment epithelium (RPE) as the instrument is rotated. This can cause further damage to the delicate tissues in the eye. 
     Some of the instruments of the present disclosure may have a distal region formed from a shape memory alloy, such as nitinol. In general, the distal regions may be formed from a material that is generally less rigid than stainless steel but more rigid than a conventional soft tip, which may be made of polyimide, for example. The distal region of the instrument may be in a relatively straight state or shape while it is introduced into the eye and may then take on a relatively curved state or shape after being introduced into the eye. For example, the temperature within the eye (e.g., body temperature around 25-37 degrees Celsius) may cause the distal tip of the instrument to return to a desired state, such as for example, a curved state, formed during fabrication of the device. 
     The present disclosure may also include methods of using such exemplary instruments to remove subretinal fluid material safely from the surface of the retina. For example, during an ophthalmic operation, such as a vitreoretinal operation, the distal tip may be placed in contact with the retina and activated to aspirate material from the surface of the retina, off of the retina, and out of the vitreous chamber of the eye. For example, during an operation, droplets of silicone oil, perfluorocarbon, blood products, or other droplets may be deposited on the retinal surface. These may be removed from the surface of the retina using the systems, methods, and instruments disclosed herein. The orientation of the side port may prevent the retina from being drawn into the side port, thereby preventing or minimizing the likelihood of harm to the retina itself. 
       FIG. 1  illustrates an exemplary implementation of an ophthalmic surgical system, generally designated as surgical system  100 . While the present disclosure applies to many different types of surgical systems other than the exemplary ophthalmic surgical system  100 , the surgical system  100  is described herein to provide appropriate context for the instruments, systems, and methods described herein. As illustrated, the surgical system  100  includes a base housing or console  102  and an associated display screen  104  that may be used to show data relating to system operation and performance during an ophthalmic surgical procedure. In some implementations, the console  102  may be mobile. For example, some implementations may include wheels or casters  106  to facilitate movement about an operating room. In some implementations, the console  102  may not include wheels. The console  102  may contain several subsystems that cooperate to enable a surgeon or other user to perform a variety of surgical procedures, such as ophthalmic surgical procedures. 
     An exemplary surgical instrument, which is illustrated as an instrument  110 , may be coupled to the console  102  by a conduit  108  and may form a part of the surgical system  100 . Embodiments of the surgical system  100  may include more than one instrument  110 . The instrument  110  represents any number of medical and/or surgical instruments, including, for example, a vitrectomy probe, an illumination probe, an aspiration probe, an irrigation probe, a drainage cannula, a phacoemulsification device, a diathermy probe, or other types of medical instruments. The instrument  110  may be a handpiece, in some implementations, such that instrument  110  is configured to be held comfortably in a user&#39;s hand for manipulation thereby. The instrument  110  may be coupled to one or more subsystems included in the console  102 . For example, the instrument  110  may be coupled to a fluidics subsystem  120  (see  FIG. 2 ) that facilitates control of a pump and/or a vacuum for use in the removal of materials, such as subretinal fluid, from the posterior segment of an eye. In some embodiments, an instrument subsystem  112  (see  FIG. 2 ) may also provide power to the instrument  110  and/or control operation of the instrument  110 . The conduit  108  may include cables, tubes, wires, fibers, or conductors, among other carriers, to provide for the operation of the instrument  110 . Some implementations may further include a footpedal  109  which can be manipulated by a user to control various aspects of the surgical system  100 , including operational parameters, such as flow rates, speeds, irrigation or aspiration, and other parameters of the instrument  110 . 
     As illustrated in  FIG. 1 , the instrument  110  may be a drainage cannula that may be used in any of a variety of ophthalmic procedures, such as an anterior segment procedure, a posterior segment procedure, a vitreoretinal procedure, a vitrectomy procedure, a cataract procedure, and/or other procedures to drain fluid from the eye. Surgical procedures other than these ophthalmic procedures may be performed by the system  100  and the instrument  110 . 
       FIG. 2  is a block diagram according to an example implementation of the surgical system  100 . The surgical system  100  may include the console  102  and several subsystems contained therein. In this example, the console  102  includes a computer subsystem  103  configured to communicate with the display screen  104  (shown in  FIG. 1 ) and with a number of subsystems that are used together to perform ophthalmic surgical procedures, such as vitreoretinal surgical procedures, for example. The computer subsystem  103  may include one or more processing devices, such as a central processing unit or central processor, and a data storage system. The data storage system may include one or more types of memory, such as RAM, ROM, flash memory, a disk-based hard drive, and/or a solid-state hard drive. The processing devices and data storage system may communicate over a bus, which may also permit communication with and between one or more of the subsystems of the surgical system  100 . 
     Some examples of subsystems in the implementation shown in  FIG. 2  may include the instrument subsystem  112 , the fluidics subsystem  120 , and a footpedal subsystem  130  including, for example, the footpedal  109 . The fluidics subsystem  120  may provide an aspiration pressure source and an irrigation pressure source. For example, in the implementation shown, the fluidics subsystem  120  includes a vacuum pump  122  and/or an irrigation pump  124 . The instrument  110  may be connected to the fluidics subsystem  120  via a fluid conduit  126 . In some instances, an instrument connected to the console  120  may be connected to one of the vacuum pump  122  or irrigation pump  124 . In other instances, an instrument connected to the console  120  may be connected to both the vacuum pump  122  and the irrigation pump  124  via respective conduits. All or a portion of the one or more fluid conduits connecting the instrument  110  to the console  120 , such as the fluid conduit  126 , may extend through the conduit  108  ( FIG. 1 ). The surgical system  100  may further include a control subsystem  140  that is coupled to a communication module  142 . The control subsystem  140  and the communication module  142  may facilitate control of the instrument  110  and/or the subsystems and other features illustrated in  FIG. 2 , such as control of the vacuum pump  122  and the irrigation pump  124  of the fluidics subsystem  120 . 
       FIG. 3  shows an exemplary instrument  110  inserted into an eye  250 . The instrument  110 , which may be referred to as a drainage cannula, includes a handle  200  having a proximal end coupled to the conduit  108  ( FIG. 1 ). The handle  200  may include a rotational structure  202  at a distal region of the handle  200 . The rotational structure  202  may rotate about a longitudinal axis  203  of the handle  200  and may have a textured or knurled surface to facilitate gripping and rotational movement by a user. The rotational structure  202  may be coupled to a first elongate tubular member  204  that extends distally from the body of the handle  200 . The first elongate tubular member  204  has a lumen extending therethrough. The lumen connects to the conduit  108  so as to be coupled to the fluidics subsystem  120 , as shown in  FIG. 2 . 
     A distal end of the first elongate tubular member  204  is coupled to a second elongate tubular member  208 . As shown, the second elongate tubular member  208  may be curved with a curvature that substantially corresponds to the radius of curvature of the interior of the eye  250 . In some instances, the radius of curvature may be around 12 mm. A 12 mm radius of curvature may correspond to the curvature of an eye of adults. In some embodiments, a portion of the second elongate tubular member  208  may have a curvature substantially corresponding to the radius of curvature of the eye  250 , while another portion of the second elongate tubular member  208  may have a curvature that does not substantially correspond to the radius of curvature of the eye  250 . The second elongate tubular member  208  may include an opening or port  210  formed through a sidewall of the elongate tubular member  208  that provides access to a lumen  212  extending within the second elongate tubular member  208  and connecting to the lumen of the elongate tubular member  204  so as to form a continuous lumen. In some implementations, the port  210  may have an oblong shape or elliptical shape and may have a smoothed edge to prevent damage to the retina. The port  210  may be an oblong or elongate port having a longitudinal or major axis extending longitudinally along a portion of the tubular member  208 . 
     In some embodiments, the port  210  may be a collection of smaller ports that function collectively to drain subretinal fluid at one location of the second elongate tubular member  208 . The port  210  may be sized such that the port  210  occupies less than a total of 90 degrees of the circumference of the second elongate tubular member  208 , in some implementations. Other implementations, the port  210  may be sized such that the port  210  occupies more or less of the circumference of the second elongate tubular member  208 . The port  210  may be the only port formed in the second elongate tubular member  208  around the circumference thereof. That is, the second elongate tubular member  208  may include a single port, i.e., port  210 . The distal tip  214  of the second elongate tubular member  208  may be capped and rounded to avoid snagging or otherwise damaging the retina  251  or RPE of the eye  250 . 
     The first and second elongate tubular members  204  and  208  may be coupled to the rotational structure  202  such that rotation of the rotational structure  202  may simultaneously cause the first and second elongate tubular members  204  and  208  to rotate as well. For example, the first and second elongate tubular members  204  and  208  may be fixed to the rotational structure  202  so that the first elongate tubular member  204 , the second elongate tubular member  208 , and the rotational structure  202  all rotate together. In some implementations, the first and second elongate tubular members  204  and  208  may be formed from different materials that have different material properties. For example and without limitation, the first elongate tubular member  204  may be formed from stainless steel, while the second elongate tubular member  208  may be formed from nitinol or another shape memory alloy. In some implementations, the first elongate tubular member  204  may generally be more rigid than the second elongate tubular member  208 . In some implementations, the second elongate tubular member  208  may be made from the shape memory alloy or a deformable polymeric material that is more rigid than silicone. More generally, the second elongate tubular member  208  may be formed from a material that may be deformed temporarily and then return to an original shape without application of an external force. 
     A benefit of the rigidity of the second elongate tubular member  208 , particularly a rigidity that is greater than one associated with soft-tipped instruments, is that the second elongate tubular member  208  is less prone to buckle or bend under pressures required to remove subretinal fluid. As a consequence, a risk associated with deflection of the second elongate tubular member  208  to one side or another during a surgical procedure, which may otherwise cause incarceration of the retina in the port  210 , may be substantially reduced or eliminated. This is an important benefit as uncontrolled buckling of an instrument towards the retina can result in incarceration of the retina, e.g., via a port formed in the instrument, or otherwise contact and injure the retina. 
     A distal region  206  of the instrument  110 , which includes the second elongate tubular member  208 , may be positioned within the vitreous chamber  252  of the eye  250  by passing through a trocar cannula  254  (shown in cross-section in  FIG. 3 ). The trocar cannula  254  may be used to form and maintain an opening through the sclera  256 . In some implementations, the trocar cannula  254  may have an interior diameter of up to 1 mm. The first and second elongate tubular members  204  and  208  may have an outer diameter ranging from about 0.3 mm to about 0.7 mm. In some implementations, the outer diameter of both the first and second elongate tubular members  204  and  208  are the same. In other implementations, the outer diameter of first and second elongate tubular members  204  and  208  may be different. For example, in some implementations, the first elongate tubular member  204  may be a 25 gauge needle, with an outer diameter less than 0.55 mm. In such implementations, the first and second elongate tubular members  204  and  208  may both have an outer diameter less than 0.55 mm. Further, the outer diameters of the first elongate tubular member  204  and the second elongate tubular member  208  may be substantially the same, and, in some implementations, the first and second elongate tubular members  204  and  208  may abut each other and be fixedly coupled together. 
     In operation, the curved second elongate tubular member may be straightened such that the second elongate tubular member  208  is longitudinally straight and aligned with the first elongate tubular member  204 . Altering the shape of the second elongate tubular member  208  in this manner provides for ease in passing the first and second elongate tubular members  204  and  208  through a lumen  258  of the trocar cannula  254 . In some implementations, the lumen  258  may be a cylindrical lumen. After the tubular member  208  has passed through the lumen  258 , tubular member  208  may return to its curved shape or state without application of external force. For example, some implementations of the second elongate tubular member  208  are deformable and biased toward a curved state. However, in such implementations, the second elongate tubular members  208  may be deformable into a straight shape to facilitate passing the second elongate tubular member  208  through the lumen  258  of the trocar cannula  254  and into the eye  250  of a patient. In still other implementations, once placed into a straightened shape, the second elongate tubular member  208  may return to a curved shape due to a change in temperature of the second elongate tubular member  208  once inserted into the eye  250 . For example, once inserted into the eye, the second elongate tubular member  208  may be warmed by the eye  250 , thereby raising a temperature of the elongate tubular member  208  above a transition temperature at which the second elongate tubular member  208  returns to its initial, curved shape. 
     For example, the tubular member  208  may be formed from nitinol or another material having a shape that is affected or controllable by temperature. The temperature at which the tubular member  208  transitions from a relatively straight state to a relatively curved state may be controlled by the proportions of nickel and titanium used in the alloy and/or by the annealing temperature used to form the tubular member  208 . As noted herein, other implementations of the tubular member  208  may be formed from other shape memory alloys or other shape memory polymers. 
     For example, the tubular member  208  may be straight or relatively straighter when at the ambient temperature of an operating room environment. After the tubular member  208  passes through the lumen  258  of the trocar cannula  254 , the exposure to body temperature within the eye  250  may cause the tubular member  208  to assume a predetermined shape or curvature. 
       FIGS. 4A and 4B  illustrate an implementation of the instrument  110 . In  FIG. 4A , the instrument  110  is shown partially inserted through the central lumen  258  of the trocar cannula  254 . The second elongate tubular member  208  is illustrated in a straightened state. This straightened state may be provided by the physical constraints of the central lumen  258  and/or by the physical properties, of the material from which the second elongate tubular member  208  is formed, e.g., temperature sensitivity associated with shape-memory materials that change shape as a result of changes in temperature.  FIG. 4B  depicts the instrument  110  as being inserted further through the trocar cannula  254  such that a portion of the first elongate tubular member  204  and the second elongate tubular member  208  extend beyond the trocar cannula  254 . For example, the first and second elongate tubular members  204  and  208  may protrude into the vitreous chamber  252  of the eye  250 , shown in  FIG. 3 . Either due to the lack of constraint imposed by the walls of the lumen  258  of the trocar cannula  254  or due to the ambient temperature within the eye  250  (or a combination thereof), the second elongate tubular member  208  assumes a curved shape. The curvature of the second elongate tubular member  208  may correspond at least in part to the curvature of the eye  250 . The shape of the port  210  may change according to the straightened or curved state of the elongate tubular member  208 . 
     Referring now to  FIGS. 5A and 5B , as shown therein, a user may manipulate the rotational structure  202  in order to rotate the first and second elongate tubular members  204  and  208  about the longitudinal axis  203 . For example, the user may desire to reorient the port  210  for insertion through a tear or opening in the retina  251  in order to drain subretinal fluid so that the retina  251  may be repositioned and reattached to the RPE/choroid. As shown in  FIG. 5A , the user may rotate the rotational structure  202  according to the arrow  500 A. By rotating the rotational structure  202  by approximately 90°, the second elongate tubular member  208  may be repositioned as seen in  FIG. 5B , such that the port  210  is in view. By moving the rotational structure  202  according to the arrow  500 B, the user may further adjust the positioning of the port  210  within the eye  250 . Thus, in some implementations, the rotational structure  202  and, hence, the first and second elongate tubular members  204  and  208  may be rotated about the longitudinal axis  203  in either of the directions corresponding to arrows  500 A and  500 B. 
     While some implementations of the instrument  110  may have a limited range of rotation, some implementations of the instrument  110  may permit the rotational structure  202  to rotate freely in either direction (clockwise or counterclockwise). Unrestricted rotation of the rotational structure may allow a user, for example, to avoid incarcerating the retina within the port  210  when draining subretinal fluid. The user may turn the rotational structure  202  to align the distal tip of the second elongate tubular member  208  with an opening in the retina. The user may also turn the rotational structure  202  in order to conform the curvature of the second elongate tubular member  208  to the curvature of the eye  250  in order to remove material from the surface of the retina, for example. 
       FIG. 6  is a flowchart of an example method  600  for utilizing an instrument, such as a drainage cannula which may be similar to instrument  110 , to remove subretinal fluid and/or material from a delicate surface, like the surface of the retina of the eye, such as the eye  250  shown in  FIG. 3 . Method  600  is illustrated in  FIG. 6  as several enumerated operations or steps. Implementations of the method  600  may include additional operations, before, after, in between, or as sub-operations of the enumerated operations. Additionally, some implementations of the method  600  may omit one or more of the enumerated operations. 
     At  602 , an instrument, such as a drainage cannula similar to the instrument  110  of  FIGS. 1-3, 4A, 4B, 5A, and 5B , may be introduced into the eye of a patient. The instrument may include a distal region with a port, which may be similar to the port  210 . At least a portion of the instrument may be inserted through a trocar cannula, which may be similar to the trocar cannula shown in  FIG. 3 , or through an incision made through the sclera of an eye. A distal region of the instrument may be positioned proximate the retina. In some implementations, the distal region of the instrument is configured to be in a straight state while passing through the incision or trocar cannula. In the case of an incision without a trocar cannula, a straight state of the distal region enables the incision to remain small, minimizing eye trauma. When within the posterior segment of the eye, a portion of the distal region may curve without the application of an external load to correspond to the shape of an average patient&#39;s eye. In some of these implementations, the port is disposed on the curved distal region. 
     At  604 , the distal region of the instrument may be positioned into subretinal space by a user. For example, the distal region of the instrument may be inserted through a retinal tear into a space occupied by subretinal fluid, as shown in  FIG. 3 . To reposition and reattach the retina, the subretinal fluid should be drained. At  606 , an aspiration pressure source may be activated to cause fluid to exit the subretinal space. For example, the aspiration pressure source may be provided by the fluidics subsystem  120  shown in  FIG. 2 . In some implementations, a naturally occurring pressure may cause the subretinal fluid to drain through the instrument. For example, if the pressure within the subretinal space is higher than the pressure within the instrument, the subretinal fluid may flow without the activation of an aspiration pressure source due to the naturally occurring pressure gradient. 
     In some implementations, the method  600  may further include  608  and  610 . These operations may be performed when the surface of the retina, or other delicate tissue, is to be cleaned. At  608 , the distal region of the instrument may be rotated by user manipulation of a rotational structure on a handle body of the instrument. For example, a second elongate tubular member, which may be similar to the second elongate tubular member  208  discussed herein, may be rotated as the rotational structure is manipulated by a user. Similarly, the rotational structure may be similar to the rotational structure  202  described herein. The second elongate tubular member may be rotated such that the port  210  is oriented perpendicular to a desired cleaning path. This orientation is illustrated in  FIG. 7 . As shown in  FIG. 7 , the first and second elongate tubular members  204 ,  208  are oriented such that the port  210  is substantially orthogonally to the retina  251 . “Substantially” is utilized here to describe the relative position of the port  251  relative to the retina  251  as both the retina  251  has a curved shape and the port  251  is formed in the second elongate tubular member  208  that also, in the implementation shown, has a tubular shape. The instrument  110  may be moved relative to the eye  250 , such as in directions into an out of the plane of the drawing and along the curvature of the eye  250  shown in  FIG. 7 . The orientation of the port  210  in the manner shown and described and movement of the instrument  110  relative to the eye as described reduces the risk of incarcerating the retina  251  within the port while removing subretinal fluid. As a result, injury to the retina is reduced. 
     In some instances, if the distal region of the instrument is oriented as desired upon insertion, it may not be necessary for the user to manipulate the instrument to rotate the second elongate tubular member as part of the method  600 . At  610 , the portion of the instrument outside the eye may be manipulated so that the second elongate tubular member travels along the retina while a pressure gradient is used to aspirate material from the eye. The instrument may work analogously to a vacuum cleaner; however, the opening of the instrument (e.g., the port in the tubular member, which may be similar to port  210  described herein) may be oriented orthogonally to or away from the surface of the retina, not oriented toward the retina. In this way, the instrument is prevented from grasping the retina itself, avoiding potential harm to the retina. Accordingly, the instrument  110  may be understood and used as a cleaning instrument configured to clean the surface of the retina. 
     The instruments, systems, and methods described herein enable a user to remove retinal fluids from between a retina and a choroid, helping retinal tissue maintain contact with the choroid after a retinal tear or detachment. As such, the retinal tissue may receive nourishment from the blood vessels within the eye and may begin to heal in place, providing a satisfactory outcome for a patient. 
     Persons of ordinary skill in the art will appreciate that the implementations encompassed by the present disclosure are not limited to the particular exemplary implementations described above. In that regard, although illustrative implementations have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.