Patent Publication Number: US-2021178081-A1

Title: Device and method for intraocular fluid injection

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/706,538, entitled, “DEVICE AND METHOD FOR INTRAOCULAR FLUID INJECTION,” filed Dec. 6, 2019, which is a continuation of and claims priority to International Patent Application No. PCT/US2019/027358, entitled, “DEVICE AND METHOD FOR INTRAOCULAR FLUID INJECTION,” filed Apr. 12, 2019, which claims the benefit of priority under 35 U.S.C. § 119 from U.S. Provisional Application No. 62/656,818, entitled “FLUID INJECTION FOR TRABECULECTOMY,” filed Apr. 12, 2018, the entirety of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Disclosed embodiments relate in general to medical devices and procedures, and more particularly to a surgical instrument and method for intraocular fluid injection. 
     BACKGROUND OF THE DISCLOSURE 
     Glaucoma refers to a group of eye conditions that cause damage to an eye&#39;s optic nerve, typically due to increased intraocular pressure (pressure in the eye). Millions of people suffer from glaucoma with symptoms that include vision loss, or in extreme cases, irreversible blindness. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide further understanding of the subject technology and are incorporated in and constitute a part of this description, illustrate aspects of the subject technology and, together with the specification, serve to explain principles of the subject technology. 
         FIGS. 1A-1C  illustrate various views of an example of a medical instrument, in accordance with some embodiments.  FIG. 1A  is a side view of the medical instrument with a coupled fluid source.  FIG. 1B  is an isometric view of the medical instrument with the fluid source removed and a fluid connector interface exposed.  FIG. 1C  is a side view of the medical instrument with a cap covering the fluid connector. 
         FIGS. 2A-2B  illustrates examples of modes of operating a medical instrument.  FIG. 2A  depicts a mode of operation in which a user actuates a button of the medical instrument using a thumb.  FIG. 2B  depicts a mode of operation in which a user actuates a button of the medical instrument using an index finger. 
         FIG. 3  illustrates a longitudinal cross-section view of a medical instrument showing an example of a fluid transfer mechanism. 
         FIGS. 4A-4B  illustrate isometric views of a medical instrument with portions of a housing removed to show a fluid transfer mechanism in various stages of operation.  FIG. 4A  illustrates the fluid transfer mechanism with the button in an upwards and non-actuated position.  FIG. 4B  illustrates the fluid transfer mechanism with the button in a depressed and actuated position. 
         FIGS. 5A-5G  illustrate various views of an example of a pre-fill component of a medical instrument.  FIG. 5A  is a side view showing the pre-fill component coupled to a handle of the medical instrument.  FIG. 5B  is a longitudinal cross-section view showing the pre-fill component coupled to the handle.  FIG. 5C  is a side view of the pre-fill component at a first stage of operation.  FIG. 5D  is a side view of the pre-fill component at a second stage of operation.  FIG. 5E  is a side view of a sealing member and an interface member of the pre-fill component.  FIG. 5F  is a longitudinal cross-section view of the sealing member of the pre-fill component.  FIG. 5G  is a side view of the interface member of the pre-fill component. 
         FIG. 6  illustrates a flow chart of an example of a method of operating a medical instrument. 
         FIG. 7  illustrates an isometric view of an example of an ophthalmic blade having a lumen. 
         FIG. 8  illustrates a side view of an example of an ophthalmic blade having a lumen. 
         FIG. 9  illustrates a front view of an example of an ophthalmic blade having a lumen. 
         FIG. 10  illustrates a rear view of an example of an ophthalmic blade having a lumen. 
         FIG. 11  illustrates an isometric view of an example of an ophthalmic blade having a lumen. 
         FIG. 12  illustrates a bottom view of an example of an ophthalmic blade having a lumen. 
         FIG. 13  illustrates a side view of an example of an ophthalmic blade having a lumen. 
         FIG. 14  illustrates a side view of an example of an ophthalmic blade having a lumen. 
         FIGS. 15A-15D  illustrate a process flow of an example of a method of operation. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below is intended as a description of various implementations and is not intended to represent the only implementations in which the subject technology may be practiced. As those skilled in the art would realize, the described implementations may be modified in various different ways, all without departing from the scope of the present disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. 
     Embodiments disclosed herein may be implemented as instruments or devices suitable for ophthalmic procedures, including, for example, devices having blades or other tools configured to cut or remove portions of tissue from a trabecular meshwork or other intraocular tissue. Some examples of such devices are disclosed in U.S. Non-Provisional application Ser. No. 15/791,204, filed on Oct. 23, 2017, and U.S. Non-Provisional application Ser. No. 15/389,328, filed on Dec. 22, 2016, the entirety of each of which is incorporated herein by reference. Embodiments disclosed herein may be implemented as devices having microcannulas or orifices configured to inject a substance into Schlemm&#39;s canal or other intraocular sites. Some examples of such devices are disclosed in U.S. Provisional Application No. 62/750,151, filed on Oct. 28, 2018, and U.S. Non-Provisional application Ser. No. 15/847,770, filed on Dec. 19, 2017, the entirety of each of which is incorporated herein by reference. 
     To facilitate the understanding of the present disclosure, a number of terms are defined below. 
     Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present disclosure. Terms such as “a,” “an,” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. 
     As used herein, the term “patient” or “subject” refers to a living mammalian organism, such as a human, monkey, cow, sheep, goat, dog, cat, mouse, rat, guinea pig, or transgenic species thereof. In certain embodiments, the patient or subject is a primate. Non-limiting examples of human subjects are adults, juveniles, infants and fetuses. 
     “Prevention” or “preventing” includes: (1) inhibiting the onset of a disease in a subject or patient which may be at risk and/or predisposed to the disease but does not yet experience or display any or all of the pathology or symptomatology of the disease, and/or (2) slowing the onset of the pathology or symptomatology of a disease in a subject or patient which may be at risk and/or predisposed to the disease but does not yet experience or display any or all of the pathology or symptomatology of the disease. 
     The term “therapeutically effective amounts” or “pharmaceutically effective amounts”, as used herein means that amount which, when administered to a subject or patient for treating a disease, is sufficient to effect such treatment for the disease or to ameliorate one or more symptoms of a disease or condition (e.g. ameliorate pain). 
     As used herein, the terms “treat” and “treating” are not limited to the case where the subject (e.g. patient) is cured and the disease is eradicated. Rather, embodiments of the present disclosure also contemplate treatment that merely reduces symptoms, improves (to some degree) and/or delays disease progression. It is not intended that embodiments of the present disclosure be limited to instances wherein a disease or affliction is cured. It is sufficient that symptoms are reduced. 
     As used herein “goniotomy” refers to a surgical procedure primarily used to treat various types of glaucoma (e.g., primary open angle glaucoma). 
     As used herein “trabecular meshwork” refers to area of tissue in the eye located around the base of the cornea, near the ciliary body, (between the scleral spur and Schwalbe&#39;s line) and is responsible for draining the aqueous humor from the eye via the anterior chamber (the chamber on the front of the eye covered by the cornea). The tissue is spongy and lined by trabeculocytes; it allows fluid to drain into a circular channel in the eye called Schlemm&#39;s canal and eventually flowing into the blood system. 
     As used herein “Schlemm&#39;s canal” refers to a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream via the collector channels and anterior ciliary veins. 
     As used herein “eye diseases” refers to various conditions of the eye including, but not limited to Glaucoma—optic neuropathy, Glaucoma suspect—ocular hypertension, Primary open-angle glaucoma, Primary angle-closure glaucoma, primary open angle glaucoma, normal or low tension glaucoma, pseudoexfoliation glaucoma, pigment dispersion glaucoma, angle closure glaucoma (acute, subacute, chronic), neovascular or inflammatory glaucoma, ocular hypertension, and other types of glaucoma that are related to dysregulation of intraocular pressure. 
     As used herein “hypotony” refers to reduced intraocular pressure. The statistical definition of hypotony is intraocular pressure (“TOP”) less than 6.5 mmHg, which is more than 3 standard deviations below the mean TOP. The clinical definition of hypotony is TOP low enough to result in pathology (vision loss). The vision loss from low TOP may be caused by corneal edema, astigmatism, cystoid macular edema, maculopathy, or other condition. Hypotony maculopathy is characterized by a low TOP associated with fundus abnormalities, including chorioretinal folds, optic nerve head edema in the acute setting, and vascular tortuosity. 
     As used herein “Schwalbe&#39;s line” refers to the anatomical line found on the interior surface of the eye&#39;s cornea, and delineates the outer limit of the corneal endothelium layer. Specifically, it represents the termination of Descemet&#39;s membrane. 
     As used herein “Descemet&#39;s membrane” refers to the basement membrane that lies between the corneal proper substance, also called stroma, and the endothelial layer of the cornea. 
     As used herein “scleral spur” refers to an annular structure composed of collagen in the human eye, a protrusion of the sclera into the anterior chamber. It is the origin of the longitudinal fibers of the ciliary muscle and is attached anteriorly to the trabecular meshwork. Open-angle glaucoma (OAG) and closed-angle glaucoma (CAG) may be treated by muscarinic receptor agonists (e.g., pilocarpine), which cause rapid miosis and contraction of the ciliary muscles, this pulls the scleral spur and results in the trabecular meshwork being stretched and separated. This opens the fluid pathways and facilitates drainage of the aqueous humour into the canal of Schlemm and ultimately decreasing intraocular pressure. 
     As used herein “Trabectome®” refers to a minimally invasive glaucoma surgical electrosurgical or ablation tool for the surgical management of adult, juvenile and infantile glaucoma. Unlike a trabeculectomy, the surgery with a Trabectome® should not create an external filtering bleb or require leaving a permanent hole in the eye. Instead, the Trabectome® electro-surgical handpiece opens access to the eyes natural drainage system. 
     Minimally invasive surgical procedures involving ocular incisions and/or intraocular fluid injection can be useful for treating glaucoma and other eye conditions. For example, in a Trabeculectomy, a surgeon can use an ophthalmic blade inserted through an incision in the eye to remove a portion of the trabecular meshwork, thereby improving outflow of the aqueous humour (AH) and relieving intraocular pressure contributing to glaucoma. 
     During the removal of the trabecular meshwork using an ophthalmic blade, some cases have been observed in which minor bleeding occurs. When bleeding occurs during the surgery, the blood can cover up the trabecular meshwork and Schlemm&#39;s canal, creating a visual obstruct. One method of dealing with the blood reflux involves removing the ophthalmic blade from the eye and inserting a viscoelastic syringe. The viscoelastic syringe can be used to push the blood reflux back into the Schlemm&#39;s canal and collecting channels or move the blood away from the trabecular meshwork. Once the blood is pushed away from the trabecular meshwork, the viscoelastic syringe is removed from the eye and ophthalmic blade is re-inserted to continue the surgery. 
     Embodiments disclosed herein include medical instruments and related methods that may be used in an ophthalmological procedure without a need for inserting and removing a separate viscoelastic syringe when such bleeding occurs. The disclosed embodiments include, among other things, a surgical instrument having an ophthalmic blade and integrated fluid delivery mechanism for intraocular injection of a viscoelastic fluid. It will be appreciated that various embodiments and principles disclosed herein may additionally or alternatively be employed for other purposes or for other medical or surgical procedures. 
     Turning now to the figures,  FIGS. 1A-1C  illustrate various views of an example medical instrument  100  that may employ principles of this disclosure.  FIG. 1A  is a side view of the instrument  100  in a configuration with a removable syringe attached.  FIG. 1B  is an isometric view of the instrument  100  in a configuration without the removable syringe and with a connector exposed.  FIG. 1C  is a side view of the instrument  100  in a configuration with a removable cap attached. 
     Referring to  FIGS. 1A-1C , the instrument  100  generally includes a tool section  102  and a handle  104 . The handle  104  is configured to interface with a fluid source  108 , and the instrument  100  is generally configured to deliver fluid to a target site. In particular, the instrument  100  may be configured to deliver fluid from the fluid source  108 , through the handle  104 , and through the tool section  102  to a target site of the patient upon actuating a fluid transfer mechanism in the handle  104 . Additionally or alternatively, the instrument  100  may be configured to transfer fluid through a channel in the handle  104  upon depressing a plunger  120  (e.g., via force applied by a finger to the proximal end of the plunger) or otherwise ejecting fluid from the fluid source  108 . 
     The handle  104  includes a housing  112  having a connector or interface for coupling to the fluid source  108 . More particularly, the housing  112  includes a luer lock connector  128  configured to removably attach to a component of the fluid source  108 , such as a syringe  124  and/or a pre-fill component  300  ( FIGS. 5A-5G ) that contains a fluid compartment (e.g., a barrel) for holding a desired liquid or substance. As appropriate, the syringe  124  may be attached or removed from the housing  112  via the luer lock connector  128  through rotational or twisting motion between the housing  112  and the syringe  124 . In some embodiments, the syringe  124  is implemented as a viscoelastic syringe for holding a viscoelastic fluid or substance of a type useful for ophthalmic procedures. The instrument  100  may be designed to handle cohesive, dispersive, or both cohesive and dispersive viscoelastic materials. Additionally or alternatively, the instrument  100  may be compatible with other fluids (e.g., saline, medicinal liquids, etc.) suitable for a variety of ocular or other medical procedures. 
     As shown in  FIG. 1C , the instrument may be further provided with a removable cap  132  that attaches to the housing  112  via the luer lock connector  128 , and which may, for example, serve to protect or isolate components of the instrument during transport or periods of non-use. It will be appreciated that while a luer lock connector  128  is shown, any of a variety of other standard or non-standard connectors may be included for fluidic coupling, as appropriate. Further, while a connector facilitating removable attachment of the fluid source  108  is shown, in some embodiments the handle  104  or the housing  112  may additionally or alternatively be provided with an integral fluid compartment for holding a desired fluid. More generally, in various embodiments the tool section  102 , handle  104 , and fluid source  108  may be removably attached, or any two or more of these components may be integrally formed or provided as a single unit. 
       FIGS. 2A-2B  are illustrations showing example modes of operating the instrument  100 . 
     As shown in  FIGS. 1A-2B , the handle  104  is equipped with a button  136  that may be used to actuate a fluid transfer mechanism. In particular, when pressed the button  136  may be configured to deliver a dosage of fluid from the syringe  124  through actuation of a fluid transfer mechanism employed in the handle  104 . The housing  112  may have a shape that permits gripping of the instrument by a human hand  140  or otherwise permits manipulation of the surgical instrument by an operator. For example, as illustrated the housing  112  may be configured as an elongate tubular or cylindrical member that permits grasping of the instrument, which facilitates precise control over incisions made with the tool section  102  or accurate insertion of the tool section  102  into a fluid injection site of a patient. An exterior surface or lateral side of the housing  112  further includes grip-enhancing features  144 , including a contoured profile and a series of ring indentations. 
     As shown in  FIGS. 2A-2B , the button  136  is disposed on a lateral side of the handle  104 . In particular, the button  136  is disposed on a lateral side of the housing  112 . This may facilitate pressing of the button  136  with ease or without a need for repositioning of the instrument  100  using a digit of the hand  140  while the instrument is manipulated using a grip that also facilitates precise control. For example, as shown in  FIG. 2A  the button  136  may be positioned in a user&#39;s hand  140  for actuation using a thumb  152 . As another example, as shown in  FIG. 2B  the button  136  may be positioned in a user&#39;s hand  140  for actuation using an index finger  148 . 
       FIG. 3  is a side view cross section of the instrument  100  illustrating components of a fluid transfer mechanism in detail.  FIG. 3  shows the handle  104  of the instrument  100  with a removable cap  132  attached and with the tool section  102  attached. In  FIG. 3 , the housing  112  is shown as being composed of several pieces rigidly fixed together, but in other embodiments, the housing  112  may be composed of one integral piece. The housing  112  may be made from any of a variety of suitable materials, such as plastics, metals, and the like. 
     As shown in  FIG. 3 , the fluid transfer mechanism includes a piston  156  disposed in an interior of the housing  112 . The piston  156  is generally configured to move relative to the housing  112 , and more particularly, is configured to reciprocate within the housing for pumping or otherwise transferring fluid. As shown in  FIG. 3 , the housing  112  is configured as an elongate tubular housing defining a longitudinal axis  160  (e.g., cylindrical axis), and the piston  156  is configured to reciprocate back and forth within an interior cavity of the housing  112  along the longitudinal axis  160  an axial direction of the housing  112 . 
     The interior cavity of the housing  112  includes one or more sealed chambers  164   a,b  that may be implemented as cylinders for compression and expansion by the piston  156 . More particularly, the interior cavity of the housing  112  includes a pair of complementary chambers, including a fluid entry chamber  164   a  and a fluid exit chamber  164   b  disposed on opposing sides of the piston  156 . The chambers are configured in a complementary fashion such that a compression stroke of the piston  156  for one of the chambers corresponds to an expansion stroke for the other chamber, and vice versa. 
     As illustrated, the entry chamber  164   a  may be sealed with an O-ring  168   a  disposed between a lateral exterior surface of the piston  156  and an interior surface of the cavity. The second chamber  164   b  may be sealed with an O-ring  168   b  disposed between a lateral exterior surface of the piston  156  and an interior surface of the cavity. More generally, in various embodiments either or both of the chambers  164   a,b  may be sealed using any of a variety of other appropriate seals or sealing elements. 
     The fluid transfer mechanism also generally includes a series of valves  172   a - d  and a fluidic channel  180  extending through the piston to facilitate compression, expansion, and transfer of the fluid within the mechanism as appropriate. As further described below, the fluid transfer mechanism may be designed to transfer fluid in a forward direction, from a proximal end to a distal end. 
     Referring to  FIG. 3 , an entry valve  172   a  is disposed at a fluid entry port of the entry chamber  164   a . The fluid entry port may be disposed at the position of the luer lock connector  128 . As shown in  FIG. 3 , the entry valve  172   a  may be fixedly attached to the housing  112  and disposed at a proximal end of the entry chamber  164   a . Alternatively, the entry valve  172   a  may be provided as part of the syringe  124  or fluid source  108  (not shown in  FIG. 3 ), or the fluid entry port may be disposed in another physical location relative to the entry chamber  164   a . The entry valve  172   a  may be a check valve (or one-way valve) of a type that permits fluid flow across it in a direction into the entry chamber  164   a  but prevents fluid flow across it in a direction out of the entry chamber  164   a.    
     An exit valve  172   b  is disposed at a fluid exit port of the exit chamber  164   b , which corresponds to the position of the tool section  102  or a tool interface  116  configured to couple to a tool section  102 . The tool interface  116  can be configured as a luer lock connector for coupling to a removable tool or provide a fixed fastening mechanism (e.g., welding, adhesives, screws, etc.) As shown in  FIG. 3 , the exit valve  172   b  may be fixedly attached to the housing  112  and disposed at a distal end of the exit chamber  164   b . Alternatively, the exit valve  172   b  may be provided as part of the tool section  102 =, or the fluid exit port may be disposed in another physical location relative to the exit chamber  164   b . The exit valve  172   b  may be a check valve of a type that permits fluid flow across it in a direction out of the exit chamber  164   b  but prevents fluid flow across it in a direction into the exit chamber  164   b.    
     One or more piston valves  172   c,d  are disposed on the piston  156  in a fluidic pathway extending through the piston  156 . In particular, the piston  156  includes a channel  180  extending through it for transferring fluid from the entry chamber  164   a  to the exit chamber  164   b , with one or more piston valves  172   c,d  disposed in the piston channel  180  or otherwise disposed in the fluidic pathway defined by the piston channel  180 . Each of the piston valves  172   c,d  may be a check valve (or one-way valve) of a type that permits fluid flow across it in a forward direction, e.g., towards a distal side or in direction extending from the entry chamber  164   a  to exit chamber  164   b , but prevents fluid flow across it in the opposite direction. 
     The piston channel  180  may optionally be segmented into a plurality of sub-channels, each terminating in a respective piston valve. For example, the piston channel  180  may include a first sub-channel terminating in a first piston valve that feeds fluid into a second sub-channel terminating in a second piston valve, and so forth. To facilitate manufacturing thereof, the piston  156  itself may be segmented into a plurality of components or pieces that are fixedly attached to one another, which may facilitate manufacturing of a piston having multiple piston channels. Alternatively, the piston  156  may be a unitary and integral construction. 
     A useful metric of a chamber may be a compression ratio (or its inverse, a expansion ratio) corresponding to a ratio of the internal volume of the chamber at is maximum and minimum points, which may correspond to a position of the piston at each end of its stroke. In various embodiments, the compression ratio or expansion ratio of a chamber may be determined by the location of the valves and diameter of the piston in the chamber. Segmenting the channel may be useful, for example, for increasing or tuning an effective compression and/or expansion ratio of one or more of the chambers for a given interior volume or piston stroke. For example, with reference to  FIG. 3 , the expansion ratio of the entry chamber  164   a  is made greater by the existence of the piston valve  172   c  between the piston valve  172   d  and entry valve  172   a , relative to if this piston valve  172   c  were omitted. Since the internal volume of the sub-channel between piston valves  172   c  and  172   d  is essentially held constant during the expansion stroke of the piston  156 , this internal volume is effectively removed from the equation. As a result, a greater expansion ratio in the entry chamber  164   a , and thus, a greater suction force across the entry valve  172   a , may be achieved for a given length of the stroke for the piston. It will be appreciated that while the example shows two piston valves and segmentation into two sub-channels, more or fewer sub-channels or piston valves may be utilized in various embodiments, as appropriate. Additionally or alternatively, adjusting the compression ratio can modify the volume of each dosage provided by the mechanism by changing a volume of fluid held in the exit chamber  164   b  that is ejected upon actuation of the piston  156 . 
     According to some embodiments, a dose adjustment member  139  can be included in the handle  104 . The dose adjustment member  139  can be, for example, a removable component or a movable component (e.g., slidable, twistable, etc.) that is configured to permit adjustment of the compression ratio. For example, the dose adjustment member  139  may be a removable component in the interior cavity of the housing  112  that can be swapped by a user or during manufacturing to tune the length of travel of the piston to adjust the compression ratio, and thereby the dosage delivered at each piston stroke or button press. As another example, the dose adjustment member  139  can be coupled to a user interface components, such as a slider or twist mechanism on the handle, that is configured to move the dose adjustment member  139  to various positions along the inner cavity of the housing  112  to constrain the travel of the piston to change the length of the piston stroke to two or more different user defined dosage volumes. 
     It will be appreciated that while a pair of complementary compression/expansion chambers  164   a,b  and corresponding valves  172   a,b  are shown, in various embodiments more or fewer chambers or valves may be included, as appropriate. For example, by eliminating one or the other of the entry chamber  164   a  or exit chamber  164   b , the cost and complexity of the device may be reduced. Control of fluid flow may be greater with an increased number of chambers and valves. 
     Referring again to  FIG. 3 , the fluid transfer mechanism may further include or otherwise cooperate with a button  136 . The button  136  is implemented as a mechanical button that is coupled to the piston  156  and configured to generate axial motion of the piston  156 . In particular, the button  136  includes an engagement member  176   a  coupled to a corresponding engagement member  176   b  of the piston  156 . The engagement members  176   a ,  176   b  can be, for example, sloped surfaces and/or wheels that are configured to engage each other to drive motion of the piston upon depression of the button  136 . For example, the engagement member  176   a  of the button  136  can be a sloped surface, such as a ramp disposed on an interior surface of the button  136 , while the engagement member  176   b  of the piston can be a complementary sloped surface, such as a ramp disposed on an exterior surface of the piston  156 . Sliding engagement between the corresponding sloped surfaces may generate axial motion of the piston  156 , as the button is depressed to convert depression of the button to distal motion of the piston. As another example, one of the button or the piston can include a sloped surface and the other of the button or the piston can include a wheel to facilitate engagement by rolling contact between the button and the piston that drives the motion of the piston upon depression of the button. Such a rolling engagement mechanism may reduce friction to facilitate smoother operation and actuation by the user. In the example shown in  FIG. 3 , the engagement member  176   a  of the button  136  includes a sloped surface, and the engagement member  176   b  of the piston includes a wheel. However, it is contemplated that these engagement members can be switched so that the button includes a wheel and the piston includes a sloped surface, for example. In the example shown, the button  136  is also pivotally attached to the housing  112  via a hinge  184 , which may permit sliding or rolling engagement between the corresponding engagement members as the button  136  pivots about the hinge  184 . 
     The piston  156  is biased to a position at an end of its stroke. This may also bias the button  136  to an upward or release position. In particular, a return spring  188  is included that biases the piston  156  towards the proximal end of the housing  112 . The return spring  188  is implemented as a coil spring disposed around a shaft of the piston  156  and coupled between an axial surface of the housing and an axial surface  192  of the piston  156 . To permit coupling in this fashion, the piston  156  includes a step disposed on its exterior surface, as shown in  FIG. 3 . It will be understood that while a return spring  188  is shown in a particular configuration, it will be appreciated the return spring may be modified or positioned differently, or any of a variety of biasing elements (e.g., magnets, torsion springs, etc.) may be used to bias the piston  156 . As but one example, while the return spring  188  is shown as an axial coil spring abutting axial surfaces of the housing  112  and the piston  156 , a similar effect may be achieved by implementing the return spring as a torsion spring in the hinge  184 . In some embodiments, both an axial spring  188  and a torsion spring in the hinge  184  may be used, where the torsion spring returns the button to a non-actuated position more quickly than the axial spring  188  returns the piston to the proximal position, thereby providing for improved user experience. Biasing the button  136  and the piston  156  in this fashion may allow each button press to trigger a single stroke of the piston  156  and, accordingly, dispense a single dosage of fluid via the fluid transfer mechanism. 
       FIGS. 4A-4B  show the instrument  100  in isometric view with portions of the housing  112  removed to allow for viewing of the fluid transfer mechanism in various stages of operation. In particular,  FIG. 4A  shows the mechanism with the piston  156  in a backwards and biased position and with the button  136  in an upwards and biased position.  FIG. 4B  shows the mechanism with the piston  156  in a forwards and actuated position and the button  136  in an actuated and depressed position.  FIGS. 4A-4B  also show in more detail an example of how engagement between the button  136  and the piston  156  can generate axial motion of the piston  156 . As the button  136  is depressed and moved from the position in  FIG. 4A  to the position in  FIG. 4B , the piston and button may roll or slide against each other to drive the piston forward. As shown in  FIG. 4A , the button  136  may further include a groove  194  for accommodating a shaft  198  of the piston and facilitating good contact between the corresponding engagement members  176   a,b  by permitting the engagement members  176   a,b  to be positioned around the shaft  198 . As shown in  FIGS. 3-4B , the piston  156  may include one or more wheels  129  that couple the piston to the housing so that the piston can roll along the housing as it translates axially, thereby reducing friction during reciprocating motion of the piston. Additionally or alternatively, it is contemplated that such the wheel  129  can be positioned on an interior side of the housing  112 . 
     It will also be appreciated that while a mechanical button is shown in various embodiments, the instrument  100  may additionally or alternatively employ any of a variety of other actuators, such as other mechanical actuators, electronic actuators, touch sensitive buttons, or the like. 
       FIGS. 4A-4B  also show a lock mechanism  190  that may be included in or otherwise cooperate with the housing  112  be configured to lock the button  136  down or lock the piston  156  in a forward position. In the example shown, the lock mechanism  190  includes a tab  189  on the button  136  that can be slide into a corresponding slot  187  on the housing  112  to hold the button  136  in a depressed position upon moving or sliding the tab. Positioning the moving tab  189  on the button may facilitate ergonomic one-handed operation, allowing the user to depress the button and operate the lock mechanism in one seamless movement. However, it is contemplated the tab is instead included on the housing  112 , which can hold the button down with or without a slot on the button (e.g., the tab can slide on top of the button when the button is depressed to avoid a need for a button slot). It is also contemplated that various other lock mechanisms may be suitably used. For example, the lock mechanism  190  can have a stop member disposed on the piston  156  (e.g., on an exterior surface thereof), a groove for accommodating the stop member when in an unlocked or biased position, and twistable member on the handle that is twistable relative to an axis of the piston  156 . Twisting the twistable member may move the lock groove out of position where it can accommodate the stop member and cause the stop member to abut a surface and hold the piston in a forward position. 
       FIGS. 5A-5G  illustrate various views of an example of a pre-fill component  300  that can be included in the medical instrument  100 .  FIG. 5A  is a side view and  FIG. 5B  is a longitudinal cross-section view showing the pre-fill component coupled to the handle of the instrument.  FIGS. 5C-5D  are side views of the pre-fill component showing movement of a sliding seal at various stages of operation.  FIGS. 5E-5G  show various views of sub-components of the pre-fill component  300  in unassembled configurations. 
     As seen in the figures, the pre-fill component  300  can contain a pre-fill chamber  330  that provides a fluid compartment from which the fluid transfer mechanism can draw fluid. The pre-fill chamber  330  can be filled with a desired fluid by coupling a syringe  124  or other fluid source to the pre-fill component during a priming or initial stage prior to a procedure. The syringe may be then removed once the pre-fill chamber  330  is filled. The pre-fill component  300  may be useful to, for example, reduce a total length of the instrument  100  by allowing the fluid transfer mechanism to draw fluid from a smaller sized or lower volume fluid compartment than in configurations where the syringe or other larger fluid source is maintained attached to the device during a medical procedure. 
     Referring to  FIGS. 5A-5B , the pre-fill component  300  can have a chamber body  340  that is coupled to the handle  104  and to the fluid transfer mechanism via an interface such as luer lock connector  128 . For example, the pre-fill component  300  can be coupled to the housing  112  via luer lock connector  128  in a manner similar to how the syringe  124  can be coupled to the luer lock connector  128  in embodiments where the syringe  124  is directly coupled to the handle (e.g., as seen in  FIG. 1A ). It is also contemplated that the pre-fill chamber body  340  may be an integral part of the handle  104  or may otherwise be fixedly coupled to the handle. 
     The pre-fill component  300  can also include another luer connector  350  (e.g., at a proximal end thereof) for connecting to the syringe  124  or other fluid source that is used to fill the pre-fill component with the desired volume of fluid. For example, the syringe  124  may be attached to the pre-fill component  300  via luer connector  350 , and the plunger  120  of the syringe may be depressed to first fill the pre-fill chamber  330  with a volume of fluid. Further depression of the plunger  120  may be used to bypass the mechanism as described above (e.g., to fully prime the instrument). 
     The pre-fill component  300  includes a mechanism to maintain a seal within the pre-fill chamber  330  upon removal of the syringe. The mechanism may be useful to, for example, avoid the potential introduction of air bubbles within the chamber or mitigate other undesirable effects upon removal of the syringe.  FIGS. 5C-5D  illustrate an operation of the mechanism of the pre-fill component  300  before and after detachment of a fluid source, such as syringe  124  (detached syringe not visible in  FIGS. 5C-5D ).  FIGS. 5E-5G  show various sub-components of the pre-fill component  300  that can be used to fill and seal the pre-fill chamber  330 . These sub-components are also shown in various assembled configurations in  FIGS. 5A-5D . 
     The pre-fill component  300  can include a sealing member  320  and an interface member  310 . The sealing member  320  is configured to seal the pre-fill chamber  330  and permit the pre-fill chamber  330  to be filled via a fill port  360  of the interface member  310 . The interface member  310  provides an interface between the pre-fill chamber  330  and the syringe used to fill the pre-fill chamber, which can be attached to the connector  350  of the interface member  310 . The mechanism can be positioned as shown in  FIG. 5C  (and  FIG. 5B ) during delivery of fluid into the pre-fill chamber  330 , where the fill port  360  is in fluid communication with the pre-fill chamber  330 . The mechanism can be configured to then move the interface member  310  and the sealing member  320  apart from each other upon detachment of the syringe, to isolate the fill port  360  from the pre-fill chamber  330 , as shown in  FIG. 5D . 
     The pre-fill component  300  can be configured as follows to facilitate isolation of the fill port  360 . The sealing member  320  can be slidably disposed in the chamber body  340 , such that it can translate axially along a longitudinal axis thereof (which can correspond to the longitudinal axis  160  of the handle). The sealing member  320  can be configured to seal the chamber, for example, via an outer O-ring  304  that is coupled between an outer surface of the sealing member  320  and an inner surface of the chamber body  340 . The outer O-ring  304  can be fixed to an outer surface of the sealing member  320  or the inner surface of the chamber body  340 . 
     The sealing member  320  can also be rotatably fixed with respect to the chamber body  340  and the handle. For example, the sealing member  320  can include one or more anti-rotation tabs  363 , which can protrude radially outward from the sealing member  320 . The anti-rotation tabs  363  can be slotted in longitudinal slots of the chamber body  340  to constrain rotational movement of the anti-rotation tabs  363  about the longitudinal axis against the longitudinal slots, while permitting axial translation of the anti-rotation tabs  363  along the longitudinal slots. It will be appreciated that this configuration can be reversed, such that the anti-rotation tabs  363  are included on the chamber body and protrude radially inward into longitudinal slots of the sealing member  320 . Various other mechanisms can be used to constrain the movement as desired. 
     The interface member  310  includes the connector  350  at its proximal end for coupling to the fluid source, and a projection  314  at its distal end that extends through an opening in the sealing member  320 . The fill port  360  is disposed on the projection  314 , and configured as a side port positioned on a lateral side of the projection  314  proximal to the terminal end at the distalmost end of the projection  314 . This configuration allows an inner O-ring  308 , disposed between an inner surface of the sealing member  320  and an outer surface of the projection  314 , to pass over the fill port  360  with relative movement between the sealing member  320  and the interface member  310 , thereby sealing the fill port  360  from the pre-fill chamber  330  or permitting the fill port  360  to fluidly communicate with the pre-fill chamber  330  depending on the relative positions of the sealing member  320  and interface member  310 . The fill port  360  can be coupled to the luer connector  350  via a lumen  311  extending partially through the interface member  310 . The inner O-ring can, for example, be held in place via a hollow set screw  322  of the sealing member, located on a distal side of the inner O-ring  308 , which can permit the projection  314  to extend therethrough. Alternatively, any other suitable mechanism can be used to hold the inner O-ring in place, such as, for example, a circumferential groove along the inner surface of the sealing member  320 . 
     The interface member  310  can be translatably fixed relative to the handle and chamber body via a retention groove  333 . A guide member  343 , such as a set screw, can be positioned in the retention groove  333 , and the retention groove can be configured as a circumferential groove on an outer surface of the interface member  310  to permit the rotation of the interface member  310  as the guide member slides along the circumferential groove. The retention groove  333  can have stops positioned at ends thereof that permit rotation of the interface member  310  within only a limited range of motion, such as 180 degrees, which corresponds to half of a circumference of the outer surface of the interface member  310 , but prevent rotation of the interface member beyond that limited range of motion upon the guide member  343  abutting the stop at the end of the groove. It will be appreciated that this can be tuned to any other limited range of rotation desired. 
     Each of the sealing member  320  and the interface member  310  include complementary spiral ramps  390 ,  392 , which are configured to mate with each other. For example, sealing member  320  can include a first spiral ramp  392  facing a proximal direction, and the interface member  310  can include a second spiral ramp  390  facing a distal direction. The mating spiral ramps are configured to urge the interface member  310  and the sealing member  320  apart from each other with relative rotation therebetween, thereby sliding the inner O-ring over the fill port  360  to isolate the fill port  360  from the pre-fill chamber. For example, as the mated spiral ramps  390 ,  392  slide over each other with rotation of the interface member  310 , the longitudinal translation constraint of the interface member coupled with the rotational constraint of the sealing member  320  causes the spiral ramp  390  of the interface member  310  to drive the sealing member  320  in a distal direction to thereby slide the inner O-ring  308  over the fill port  360 , as seen in  FIG. 5D . 
     An operation of the pre-fill component may thus be as follows. First, a user may attach a syringe to the luer connector  350  of the interface member  310 , by rotating the syringe about the longitudinal axis in a first direction (e.g., clockwise). The guide member  343  may abut against a first stop at a first end of the circumferential retention groove  333  to permit the syringe to be tightened against the luer connector  350  as it is rotated in the first direction. 
     Next, the user may depress the plunger of the syringe to deliver fluid into the pre-fill chamber  330  through the luer connector. The user may further depress the plunger to prime the fluid transfer mechanism downstream from the pre-fill chamber after the pre-fill chamber has been filled, where depression of the plunger bypasses the check valves in the fluid transfer mechanism. 
     Once the instrument is primed, the user may begin to remove the syringe by rotating the syringe in a second direction, opposite the first direction (e.g., counter-clockwise). The rotation to remove the syringe may have two phases. 
     During the first phase, the interface member  310  rotates together with the syringe, as the guide member slides along the retention groove away from the first stop, along the groove, and towards the second step. As the interface member  310  rotates about the longitudinal axis together with the syringe, the spiral ramp  392  of the interface member urges movement of the sealing member  320  distally along the longitudinal axis, causing the interface member  310  and the sealing member  320  to separate from each other until the inner O-ring  308  slides past the fill port  360  to isolate the fill port  360  from the pre-fill chamber  330 , and thus isolate the pre-fill chamber  330  from the syringe. As the syringe has been rotating together with the interface member  310  thus far, the seal between the syringe and the luer connector  350  remains intact and no air is introduced into the device. 
     After the inner O-ring passes over the fill port  360 , the interface member  310  reaches the end of its limited rotational travel as the guide member  343  abuts the second stop at the opposite end of the retention groove  333  from the first stop. After this, the second phase of rotation is reached. During this second phase, the further rotation of the syringe disconnects the syringe from the luer connector  350  of the interface member, as the interface member is constrained from further rotation by the second stop. As the fill port  360  is now isolated from the pre-fill chamber, any air introduced by the disconnection of the syringe is prevented from reaching the pre-fill chamber. 
     Finally, after the syringe has been removed, the user (e.g., surgeon or medical practitioner) may operate the fluid transfer mechanism to deliver doses of fluid from the pre-fill chamber. The sealing member  320  may operate as a plunger at this stage, where each dosage of fluid caused by actuating the button draws the sealing member  320  forward distally by an amount of one dosage volume unit. 
     Referring now to  FIG. 6 , an example method of operation is depicted.  FIG. 6  shows a process flow and a schematic diagram of the surgical instrument  100  with various details omitted for simplicity. In  FIG. 6 , valves  172   a - d  are depicted schematically as open or closed during each stage, with corresponding arrows depicting a direction of fluid flow across the valve where appropriate. 
     At step  202 , a user may attach a syringe  124  to the housing  112 . The syringe  124  may be attached using a luer lock connector or other suitable connection interface, as described above. At this stage, the fluid transfer mechanism is in a steady state and no fluid is flowing through the fluid transfer mechanism. 
     At step  206 , a user may prime the instrument  100 . In particular, the plunger  120  of the syringe  124  may be depressed, or fluid  204  may otherwise be ejected from the syringe  124 , which may cause a cracking pressure of each of the valves  172   a - d  to be exceeded and cause fluid to flow through each of the valves  172   a - d , and through the entire housing  112 , in the forward direction. Once fluid is ejected from the tool or tip of the instrument, air bubbles may be removed and the instrument may be primed for fluid delivery to the intended target site, as appropriate. Additionally or alternatively, a similar process of depressing the plunger  120  may be used to bypass the fluid transfer mechanism and deliver a steady dosage of fluid, as desired. In particular, a cracking pressure of each of the valves  172   a - d  may be configured to be exceeded upon a depression of the plunger  120 . In the example shown, the syringe  124  remains attached to the instrument during the remainder of the procedure to supply the fluid  204  delivered by the piston pump mechanism. In other embodiments, priming the instrument  100  may fill a pre-fill chamber as described herein. This may allow the syringe  124  to be removed at this stage, as fluid  204  delivered during the procedure via the piston pump mechanism can be drawn from the pre-fill chamber in the remaining steps. 
     At step  210 , a user may press the button, or a forward stroke of the piston  156  may be otherwise actuated. As shown in  FIG. 6 , during the forward stroke of the piston  156  the entry chamber  164   a  may expand, generating a pressure differential or suction force across the entry valve  172   a  that exceeds its cracking pressure and causes fluid to be drawn into the entry chamber  164   a  from the fluid compartment. Simultaneously, or during the same forward stroke, the exit chamber  164   b  compresses, causing a cracking pressure of the exit valve  172   b  to be exceeded and causing fluid to be ejected from the chamber  164   b . In this fashion, a dosage of viscoelastic fluid or other fluid may be delivered to a blade, or other surgical tool, or otherwise delivered to a target site. Since the piston valves  172   c,d  restrict entry to only the forward direction, they remain closed during the forward stroke and facilitate compression and expansion of the chambers  164   a,b , as described above. 
     At step  214 , a user may release the button, or a backward stroke of the piston  156  may be otherwise initiated. As shown in  FIG. 6 , during the backward stroke of the piston  156  the exit chamber  164   b  expands and the entry chamber  164   a  compresses. At the same time, the piston valves  172   c,d  open and permit forward fluid flow across them, thus transferring fluid from the entry chamber  164   a  to the exit chamber  164   b  as the entry valve  172   a  and exit valve  172   b  remain closed. This may return the piston  156  to its biased position where it is ready to deliver another dosage of fluid. 
     It will be appreciated that embodiments disclosed herein may be useful for medical and surgical procedures. There are numerous medical and surgical procedures in which it is desirable to cut and remove a strip of tissue of controlled width from the body of a human or veterinary patient. For example, it may sometimes be desirable to form an incision of a controlled width (e.g., an incision that is wider than an incision made by a typical scalpel, cutting blade or needle) in the eye, skin, mucous membrane, tumor, organ or other tissue or a human or animal. In addition, it may sometimes be desirable to remove a strip or quantity of tissue from the body of a human or animal for use as a biopsy specimen, for chemical/biological analysis, for retention or archival of DNA identification purposes, etc. In addition, some surgical procedures require removal of a strip of tissue of a known width from an anatomical location within the body of a patient. 
     One surgical procedure wherein a strip of tissue of a known width is removed from an anatomical location within the body of a patient is an ophthalmological procedure used to treat glaucoma. This ophthalmological procedure is sometimes referred to as a goniotomy. In a goniotomy procedure, a device that is operative to cut or ablate a strip of tissue of approximately 2-10 mm in length or more and about 50-230 μm in width is inserted into the anterior chamber of the eye and used to remove a full thickness strip of tissue from the trabecular meshwork. The trabecular meshwork is a loosely organized, porous network of tissue that overlies a collecting canal known as Schlemm&#39;s canal. A fluid, known as aqueous humor, is continually produced in the anterior chamber of the eye. In healthy individuals, aqueous humor flows through the trabecular meshwork, into Schlemm&#39;s canal and out of the eye through a series of ducts called collector channels. In patients who suffer from glaucoma, the drainage of aqueous humor from the eye may be impaired by elevated flow resistance through the trabecular meshwork, thereby resulting in an increase in intraocular pressure. The goniotomy procedure can restore normal drainage of aqueous humor from the eye by removing a full thickness segment of the trabecular meshwork, thus allowing the aqueous humor to drain through the open area from which the strip of trabecular meshwork has been removed. 
     Embodiments disclosed herein can be used for surgical medicinal intervention. For example, some embodiments relate to a microsurgical device and methods of its use for treatment of various medical conditions including but not limited to eye diseases, such as glaucoma, using minimally invasive surgical techniques. In some embodiments, the device may be a dual-blade device for cutting the trabecular meshwork (“TM”) in the eye. For example, the device may have a device tip providing entry into the Schlemm&#39;s canal via its size (i.e., for example, between approximately 0.2-0.3 mm width) and a configuration where the entry blade tip ramps upwardly providing a wedge or ramp-like action for cutting the TM. Alternatively, a single incision device tip such as a microvitreoretinal (“MVR”) blade (BD, Franklin Lakes, N.J., USA) or a cautery device tip such as a Trabectome® device may be used. In some embodiments, the tool section  102  of the device can include a cannula, a microcannula, or dual-blade tool having a lumen for delivering fluid such as, for example those described in U.S. Non-Provisional application Ser. No. 15/791,204, filed on Oct. 23, 2017, U.S. Non-Provisional application Ser. No. 15/389,328, filed on Dec. 22, 2016, U.S. Provisional Application No. 62/750,151, filed on Oct. 28, 2018, or U.S. Non-Provisional application Ser. No. 15/847,770, filed on Dec. 19, 2017, the entirety of each of which is incorporated herein by reference. 
     Turning now to  FIG. 7 , an example dual blade tool for treatment of glaucoma is illustrated. In some embodiments, the tool may be included in the tool section  102  of the instrument  100 . In particular, the tool is illustrated to reveal the dual cutting blades (arrows) as well as the distal point (asterisk) that is designed to pierce the trabecular meshwork (“TM”) and enter into the Schlemm&#39;s canal. Once in the canal, the tool is advanced so that the TM moves up the ramp from the distal point toward the dual cutting blades, which then cleanly incise the presented TM. The distance between the dual blades is designed to closely match that of the width of the TM across a range of human eyes. 
     Referring now to  FIGS. 8-10 , a device  12  is shown. In some embodiments, the device  12  may be implemented as an ophthalmic blade that can be included in a distal end of the tool section  102  of the instrument  100  described above. The device  12  may further include a lumen  199  that provides a fluidic pathway for delivery or injection of fluid received from a fluid transfer mechanism included in a handle  104 . As shown in  FIG. 8 , a platform  5  of the device  12  can include a tip  6  at a distal side of the platform  5  and a top surface (e.g., ramp)  13  extending from the distal side of the platform  5  to a proximal side of the platform  5 , opposite the distal side of the platform  5 . For example, the top surface  13  can extend from the tip  6  to one or more lateral elements  10 ,  11 . 
     As further shown in  FIG. 8 , the platform  5  can include a bottom surface  15  extending from the tip  6  at the distal side of the platform  5  to a rear portion  7  of the platform  5 , opposite the tip  6 . The bottom surface  15  of the device  12  can be positioned opposite the top surface  13 . The bottom surface  15  can be configured to abut the outer wall of the Schlemm&#39;s canal during a procedure (see  FIGS. 15A-15C ). At least a portion of the bottom surface  15  can be flat and/or planar. The rear portion  7  can define a curved or round surface that transitions from the bottom surface  15  to a portion of the shaft  4 . 
     As shown in  FIGS. 9 and 10 , opposing sides  8 ,  9  of the platform  5  can extend downwardly from the top surface  13 . The opposing sides  8 ,  9  can be planar and/or parallel to each other. The top surface  13  can transition to the opposing sides  8 ,  9  with a transition feature. While a round bevel is shown in  FIGS. 8-10 , the transition feature can have one or more other shapes, including curved, round, chamfer, fillet, etc. 
     A transition feature can be provided between the bottom surface  15  and the opposing sides  8 ,  9 . For example, the bottom surface  15  can transition to the opposing sides  8 ,  9  with transition sections  28 ,  29 , respectively. While chamfers are shown for transition sections  28 ,  29  in  FIGS. 8-10 , the transition feature can have one or more other shapes, including curved, round, beveled, fillet, etc. Along the transition features, the width of the device  12  can transition from a first width, between the opposing sides  8 ,  9 , to a second width, less than the first width, across the bottom surface  15 . The transition from the first width to the second width can be gradual, linear, stepwise, or another type of transition. 
     Referring now to  FIGS. 10-12 , the bottom surface  15  of the device  12  can include surface features that enhance interactions with the outer wall of the Schlemm&#39;s canal during a procedure. For example, the bottom surface  15  can be planar, convex, concave, or combinations thereof. By further example, as shown in  FIGS. 11 and 12 , the bottom surface  15  can include a recessed portion  40  between at least two protrusions. The recessed portion  40  can be defined by a gap, space, or void. A first protrusion  38  can be positioned below the first side  8  and/or the first transition section  28  of the platform  5 . The first protrusion  38  can be formed, at least in part, by at least a portion of the first transition section  28 . A second protrusion  39  can be positioned below the second side  9  and/or the second transition section  29  of the platform  5 . The second protrusion  39  can be formed, at least in part, by at least a portion of the second transition section  29 . Each of the protrusions  38 ,  39  can extend from the rear portion  7  of the platform  5  toward the tip  6 . The protrusions  38 ,  39  can be separated by a recessed portion  40  extending there between. As shown in  FIGS. 10 and 11 , a transition between the protrusions  38 ,  39  and the recessed portion  40  can be stepwise, forming one or more edges. Additionally or alternatively, a transition between the protrusions  38 ,  39  and the recessed portion  40  can be gradual, curved, round, beveled, chamfered, linear, or another type of transition. For example, the recessed portion  40  can include a concave feature. The recessed portion  40  can extend to and intersect the rear portion  7  of the platform  5 . 
     Adjacent to the tip  6 , the bottom surface  15  can provide a continuous (e.g., planar) portion  16  that is not interrupted by the recessed portion  40 . The tip  6  can be separated from the recessed portion  40  by the continuous portion  16 . Accordingly, the bottom surface  15  can include a planar distal portion and a non-planar proximal portion along the length thereof. The tip  6  and the region (e.g., continuous portion  16 ) immediately proximal to the tip  6  can be continuous, such that the recessed portion  40  does not intersect the tip  6 . The recessed portion  40  can extend distally from the rear portion  7 , for example, not farther than the opposing sides  8 ,  9  and/or the transition sections  28 ,  29 . As shown in  FIG. 12 , the recessed portion  40  can terminate on a distal end thereof with a transition feature that is, for example, gradual, curved, round, beveled, chamfered, linear, stepwise, or another type of transition. 
     The planar distal portion can provide an even surface to facilitate entry into tissue with the tip  6 . The nonplanar proximal portion (e.g., the protrusions  38 ,  39  and the recessed portion  40 ) can interact with the Schlemm&#39;s canal during a procedure. As the platform  5  is moved, at least some of the tissue can be received within the recessed portion  40  between the protrusions  38 ,  39 . The protrusions  38 ,  39  provide a smaller surface area for exposure to the tissue (e.g., Schlemm&#39;s canal). Accordingly, the nonplanar proximal portion of the bottom surface  15  provides greater maneuverability of the platform  5  as it moves along the tissue. 
     Referring now to  FIG. 13 , a cross section view of a device similar in some respects to that shown in  FIGS. 8-12  is depicted. The device further includes an angle (e.g., 4 degrees) on a vertical shaft that allows for a lumen  199  down the shaft. In particular, the angle between the bottom surface  15  and a back surface of the platform  5  is obtuse, and the back surface is positioned approximately 4 degrees apart relative to a normal of the bottom surface. 
     Referring now to  FIG. 14 , a cross section view of a device is depicted. In particular, the device is a tool containing an ophthalmic blade of a type similar to those described above with reference to  FIGS. 8-13 . The device further includes a lumen  199  that may be used for fluid delivery. For example, the lumen  199  may be configured to receive viscoelastic fluid from a fluid transfer mechanism and deliver the viscoelastic fluid to a trabecular meshwork or otherwise inject fluid to an intraocular cavity. 
       FIGS. 15A-15D  illustrate an example device and method of operation that may be employed in some embodiments of the instrument  100 . In particular,  FIGS. 15A-15D  show operation of an ophthalmic blade that may be integrated in the tip of the tool section  102  (see, e.g.,  FIG. 1 ) and applied to a trabecular meshwork.  FIGS. 15A-15D  also show a lumen  199  that may be used for fluid delivery during the method. 
     The device may be introduced through a clear corneal incision on an eye (e.g., incision size between 0.5 and 2.8 mm in width) and advanced through an anterior chamber of the eye, either across the pupil or across the body of the iris to engage the trabecular meshwork (TM) on the opposite side of the anterior chamber. The anterior chamber is filled with aqueous humor and, by way of example, may have a volume of approximately 0.25 milliliter (ml) and be approximately 3 millimeter (mm) deep. The anterior chamber may be filled with viscoelastic to replace the aqueous humor and stabilize the chamber during the procedure. Accordingly, approximately 0.25 ml may be injected into the chamber at this stage of the surgery. The viscoelastic may be injected into the anterior chamber using a syringe. In some embodiments, the viscoelastic may be injected by depressing plunger  120  or otherwise ejecting fluid from the syringe  124  in a manner that bypasses a fluid transfer mechanism in the instrument  100  (see  FIGS. 1-6 ) and causes fluid to flow through the lumen  199 . Additionally or alternatively, actuation of the fluid transfer mechanism (e.g., via button  136 ) may be used. In some embodiments, each button press may be configured to deliver only a small single dosage of fluid (e.g., approximately 0.03 to 0.05 ml of viscoelastic with each button press). In these cases, the bypass mechanism may be useful for allowing the anterior chamber to be initially filled with a larger volume of viscoelastic without a need for a separate syringe. Further, this may allow the fluid transfer to be used later during the procedure to deliver smaller dosages as appropriate, without a need for the surgeon to change their grip during operation. 
     As shown for example in  FIG. 15A , once the target tissue  20  (e.g., TM) is reached, the tip  6  of the device may be then used to enter into Schlemm&#39;s canal (“SC”)  22 . According to some embodiments, for example as shown in  FIG. 15A , the ramp  13  may be used to elevate the TM  20  away from the outer wall of the Schlemm&#39;s canal  22 . According to some embodiments, for example as shown in  FIG. 15B , the advancement of the platform  5  can stretch the TM  20  as it travels up the ramp  13  without tearing a strip  20   a  of the TM  20  that is on the ramp  13 . For example, the first side  8  and the second side  9  can allow the TM  20  on the ramp  13  (e.g., distal to the first and second lateral blades  10 ,  11 ) to remain connected to the TM  20  that is not elevated by the ramp  13 . As the TM  20  is elevated, it is under tension that is greater than the tension of the TM  20  when not elevated from the SC  22 . Advancement of the ramp  13  facilitates presentation of the TM  20  to the first and second lateral blades  10 ,  11 . According to some embodiments, for example as shown in  FIG. 15C , the TM  20  contacts the first and second lateral blades  10 ,  11  while the TM  20  is elevated (e.g., stretched and/or under tension). In this configuration, the first and second lateral blades  10 ,  11  incise first and second incisions into the TM  20  to form the strip  20   a  of the TM  20 . The incision is more easily and precisely made due to the elevation of the TM  20 . During advancement of the platform  5 , at least a portion of the strip  20   a  can be received within the gap  14  between the first and second lateral blades  10 ,  11 . The strip  20   a  can have a width W that corresponds to the distance D across the gap  14 . The width W can be measured along the X-axis, such as across the first and second incisions and transversely (e.g., orthogonally) to the direction of advancement of the device  12  to form the strip  20   a . The distance D can be measured along the X-axis, such as across the first and second lateral blades  10 ,  11  and transversely (e.g., orthogonally) to the direction of advancement of the device  12  to form the strip  20   a . According to some embodiments, for example as shown in  FIG. 15D , the strip  20   a  that has been separated from a remainder of the TM  20  can be removed by a device  30  (e.g., forceps) or by aspiration. 
     In some cases, bleeding may occur during removal of the TM  20  or during the steps depicted in  FIGS. 15B-15C . When this occurs, the surgeon may actuate the fluid transfer mechanism (e.g., press button  136 , see  FIGS. 1-6 ) to deliver a dosage of viscoelastic. This may push the blood back into the SC  22  or otherwise move the blood away from the TM  20 , allowing the surgeon to continue the procedure without a need for removing the device from the anterior chamber to insert a separate viscoelastic syringe. 
     The advancement of the platform  5  and the ramp  13  can proceed as the device advances clockwise or counterclockwise. The distal cutting portion is angled so that the dual blades are placed in optimum cutting position. This angle may be such that the cutting tip bends to conform to the area between Schwalbe&#39;s line and the scleral spur (SS), an area that encompasses SC. SC is narrow near the cornea and wider near the SS and thus an angled tip is best to present the tissue  20  to the two edges of the TM. The ramp  13  of the cutting tip may be angled so that the tissue  20  is constantly elevated towards the blade as the tip is advanced in circumferential pattern. Between the cutting tip and the first and second lateral blades  10 ,  11 , the ramp  13  is shaped to avoid cutting tissue, such that the TM  20  that is elevated away from the outer wall of the Schlemm&#39;s canal  22  remains intact as it advances along the ramp  13 . For example, the ramp  13  can include convex or beveled edges that are not sharp enough to cut the TM  20 . Endoscopic visualization may also be used to guide the cutting. In some embodiments, the device of the present disclosure may be placed at the end of an endoscope, precluding the need for a gonio lens during treatment. In some embodiments, the device of the present disclosure may be place at the end of an endoscope and the TM may be engaged under direct visualization of the endoscope camera. 
     A reference to an element in the singular is not intended to mean one and only one unless specifically so stated, but rather one or more. For example, “a” module may refer to one or more modules. An element proceeded by “a,” “an,” “the,” or “said” does not, without further constraints, preclude the existence of additional same elements. 
     Headings and subheadings, if any, are used for convenience only and do not limit the invention. The word exemplary is used to mean serving as an example or illustration. To the extent that the term include, have, or the like is used, such term is intended to be inclusive in a manner similar to the term comprise as comprise is interpreted when employed as a transitional word in a claim. Relational terms such as first and second and the like may be used to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. 
     Phrases such as an aspect, the aspect, another aspect, some aspects, one or more aspects, an implementation, the implementation, another implementation, some implementations, one or more implementations, an embodiment, the embodiment, another embodiment, some embodiments, one or more embodiments, a configuration, the configuration, another configuration, some configurations, one or more configurations, the subject technology, the disclosure, the present disclosure, other variations thereof and alike are for convenience and do not imply that a disclosure relating to such phrase(s) is essential to the subject technology or that such disclosure applies to all configurations of the subject technology. A disclosure relating to such phrase(s) may apply to all configurations, or one or more configurations. A disclosure relating to such phrase(s) may provide one or more examples. A phrase such as an aspect or some aspects may refer to one or more aspects and vice versa, and this applies similarly to other foregoing phrases. 
     A phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list. The phrase “at least one of” does not require selection of at least one item; rather, the phrase allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, each of the phrases “at least one of A, B, and C” or “at least one of A, B, or C” refers to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C. 
     It is understood that the specific order or hierarchy of steps, operations, or processes disclosed is an illustration of exemplary approaches. Unless explicitly stated otherwise, or the context clearly dictates otherwise, it is understood that the specific order or hierarchy of steps, operations, or processes may be performed in different order. Some of the steps, operations, or processes may be performed simultaneously. The accompanying method claims, if any, present elements of the various steps, operations or processes in a sample order, and are not meant to be limited to the specific order or hierarchy presented. These may be performed in serial, linearly, in parallel or in different order. 
     In one aspect, a term coupled or the like may refer to being directly coupled. In another aspect, a term coupled or the like may refer to being indirectly coupled. 
     Terms such as top, bottom, front, rear, side, horizontal, vertical, and the like refer to an arbitrary frame of reference, rather than to the ordinary gravitational frame of reference. Thus, such a term may extend upwardly, downwardly, diagonally, or horizontally in a gravitational frame of reference. 
     The disclosure is provided to enable any person skilled in the art to practice the various aspects described herein. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the subject technology. The disclosure provides various examples of the subject technology, and the subject technology is not limited to these examples. Various modifications to these aspects will be readily apparent to those skilled in the art, and the principles described herein may be applied to other aspects. 
     All structural and functional equivalents to the elements of the various aspects described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for”. 
     The title, background, brief description of the drawings, abstract, and drawings are hereby incorporated into the disclosure and are provided as illustrative examples of the disclosure, not as restrictive descriptions. It is submitted with the understanding that they will not be used to limit the scope or meaning of the claims. In addition, in the detailed description, it can be seen that the description provides illustrative examples and the various features are grouped together in various implementations for the purpose of streamlining the disclosure. The method of disclosure is not to be interpreted as reflecting an intention that the claimed subject matter requires more features than are expressly recited in each claim. Rather, as the claims reflect, inventive subject matter lies in less than all features of a single disclosed configuration or operation. The claims are hereby incorporated into the detailed description, with each claim standing on its own as a separately claimed subject matter. 
     The claims are not intended to be limited to the aspects described herein, but are to be accorded the full scope consistent with the language of the claims and to encompass all legal equivalents. Notwithstanding, none of the claims are intended to embrace subject matter that fails to satisfy the requirements of the applicable patent law, nor should they be interpreted in such a way.