Patent Description:
The implantation of a shunt connecting the anterior chamber of the ocular globe and the subarachnoid space is a procedure which, in order to be successful, needs to overcome the following difficulties: creating a clear passage from an external side of the optic nerve sheath to access the optic nerve sheath; penetrating the optic nerve sheath to access the subarachnoid space; ensuring a fluid-tight seal of the optic nerve sheath around the shunt; preventing damage to the optic nerve; preventing migration of the shunt; preventing shunt erosion through the conjunctiva; preventing blockage of the shunt by iris tissue and preventing corneal endothelial decompensation.

The subarachnoid space surrounding the optic nerve is formed between the optic nerve and the sheath and is filled with cerebrospinal fluid. Cerebrospinal fluid has a chemical composition comparable to that of the aqueous fluid of the eye. The pressure within cerebrospinal fluid normally varies between 5mmHg and 15mmHg.

The ocular globe of the eye has a tough outer layer comprised of the sclera and the cornea. The ocular globe maintains an internal pressure known as the intraocular pressure which normally varies between 10mmHg and 21mmHg. The intraocular pressure needs to be controlled within a defined range in order for the eye to function normally.

The intraocular pressure is regulated by maintaining a balance between volumes of aqueous fluid produced and drained from the anterior chamber of the ocular globe. Aqueous is produced by the ciliary body and drained through the trabecular and uveoscleral pathways. If an imbalance occurs in the amount of aqueous produced or drained from the ocular globe, then the intraocular pressure becomes too high or too low.

The lamina cribrosa separates the intraocular and subarachnoid fluid compartments. The presence of raised intraocular pressure or low intracranial pressure results in a large pressure differential across the lamina cribrosa (translaminar pressure). This causes damage to the optic nerve head known as glaucoma. Glaucoma causes irreversible visual field defects. These defects enlarge until a patient's field of view is severely restricted. In the end stage of the disease, total vision loss occurs. Glaucoma is a leading cause of blindness worldwide. If the intraocular pressure remains very high, the eye can become persistently painful and may need to be removed.

Current medical and surgical treatment options for glaucoma are aimed at lowering intraocular pressure. These treatments have various shortcomings. Glaucoma which is difficult to control is often managed by inserting a glaucoma drainage device. These devices drain the excess fluid out of the anterior chamber of the eye into one of <NUM> anatomical areas:.

This space is not adapted to the presence of pressurised aqueous fluid. The aqueous therefore incites an inflammatory response which results in the formation of a fibrovascular "bleb". Consequently, there is a high rate of complications, unpredictable outcomes and treatment failure.

This space is highly vascular and thus there is a high risk of bleeding. Outcomes are unpredictable and there is a high rate of failure.

Only a small amount of fluid can drain through this space and thus the effect of these devices is minimal and treatment failure is common.

The prior art does not disclose or propose ocular shunts having a two part construction where the distal shunt portion comprising a flexible distal tube and the proximal shunt portion comprising a rigid proximal tube are releasably connected to one another.

A shunt according to the preamble of claim <NUM> is known from the document <CIT>.

It is an object of the present invention to provide a shunt system for draining excess fluid out of the ocular anterior chamber into the orbital subarachnoid space. This has the following advantages: Immediate, predictable, regulated and long-term pressure control, eradication of translaminar pressure, no bleb complications and less risk of intraocular bleeding.

Longstanding low intraocular pressure occurs when the ciliary body stops producing aqueous fluid. Phthisis is a disease caused by chronic low intraocular pressure wherein the ocular globe loses its integrity, stops functioning and shrivels up into a prune-like structure resulting in permanent and irreversible destruction of the eye. Phthisis is a leading indication for removal of an eye. Currently, no medical or surgical treatment options exist which can effectively reverse chronically low intraocular pressure.

The cerebrospinal fluid pressure is controlled by maintaining a balance between volumes of cerebrospinal fluid produced and drained from the subarachnoid space. Cerebrospinal fluid is produced by the choroid plexuses and drained through the arachnoid granulations. If more cerebrospinal fluid is produced than is drained from the subarachnoid space, then the cerebrospinal fluid pressure becomes too high. This can cause damage to the optic nerve head due to reversed translaminar pressure. Idiopathic Intracranial Hypertension is a condition where longstanding raised intracranial pressure causes loss of vision.

It is a further object of the present invention to provide a shunt system for connecting the ocular globe and subarachnoid space to allow cerebrospinal fluid to flow into the ocular globe until the intraocular pressure is equal to the intracranial pressure, thereby preventing the onset of phthisis and Idiopathic Intracranial Hypertension.

In a specific application, the implantation of a shunt for the regulation of intraocular pressure in order to ameliorate the abovementioned ocular diseases.

According to a first aspect of the invention there is provided shunt (<NUM>, <NUM>) for treating an ocular disorder related to a disorder of intraocular or intracranial pressure by regulating intraocular pressure in an eye of a patient, the shunt comprising a proximal shunt portion defining a proximal end (<NUM>, <NUM>) which is implantable in an ocular anterior chamber (A) of a patient and a distal shunt portion defining a distal end (<NUM>, <NUM>) which is implantable in a subarachnoid space (B) of the patient, the shunt defining a lumen (<NUM>, <NUM>) extending longitudinally between the distal and proximal ends, the shunt having an enlarged distal stop formation (<NUM>, <NUM>) near the distal end of the shunt, which is disposed in the subarachnoid space after implantation of a distal end region of the shunt in the subarachnoid space, for resisting withdrawal of the shunt after implantation in the subarachnoid space, and being flexible along a portion of a length of the shunt so as to conform to an outer anatomical curvature of the ocular globe (N), characterized in that the proximal shunt portion includes at least one outwardly-projecting ridge formation (<NUM>) for resisting migration of the proximal shunt portion after implantation thereof in the ocular anterior chamber, and wherein the distal shunt portion comprising a flexible distal tube and the proximal shunt portion comprising a rigid proximal tube are releasably connected to one another with the lumen of the shunt extending continuously through the distal and proximal shunt portions.

The shunt may have an enlarged proximal stop formation (<NUM>, <NUM>) near the distal end of the shunt disposed at a position spaced from the distal stop formation at a location relatively closer to the proximal end of the shunt, the proximal stop formation being disposed externally of an optic nerve sheath (D) upon implantation of the distal end of the shunt in the subarachnoid space surrounded by the optic nerve sheath, thereby preventing over-migration of the shunt into the subarachnoid space.

The shunt may comprise a distal shunt portion defining the distal end of the shunt and a proximal shunt portion defining the proximal end of the shunt.

The distal shunt portion may be of a flexible construction along a portion of a length thereof and wherein the proximal shunt portion is of a rigid construction facilitating advancement of the proximal shunt portion along a scleral passageway defined in the sclera extending to the ocular anterior chamber.

The distal shunt portion may be flexible along an entire length thereof.

The distal shunt portion may comprise an elongate flexible tubular body and a rigid implant body connected to a distal end of the flexible tubular body, which defines the distal end of the shunt.

The distal end of the shunt may have a tapered end region tapering towards the distal end of the shunt, for facilitating advancement of the distal end region of the shunt along a passageway defined in the optic nerve sheath.

The implant body may define the distal stop formation and the proximal stop formation.

A cross-sectional width of the proximal stop formation may be less than a cross-sectional width of the distal stop formation.

The proximal shunt portion may have a straight section (<NUM>) at a proximal end region of the shunt terminating in the proximal end of the shunt, permitting the straight section to be displaced along a scleral passageway defined in the sclera extending to the ocular anterior chamber.

A proximal end region of the proximal shunt portion may taper towards the proximal end of the shunt, thereby facilitating displacement of the proximal shunt portion along the scleral passageway.

A wall of the proximal shunt portion may have an opening at the proximal end thereof and at least one opening in a side thereof thereby permitting drainage of aqueous fluid into the lumen of the shunt from different directions.

The proximal shunt portion may have a curved section (<NUM>) spaced from the proximal end of the shunt, the curved section having a curvature which conforms to an anatomical curvature of the ocular globe.

The proximal shunt portion may include at least one outwardly-projecting ridge formation for resisting migration of the proximal shunt portion after implantation thereof in the ocular anterior chamber.

The proximal shunt portion may include a number of the ridge formations in a longitudinally-spaced arrangement near the proximal end of the shunt.

The proximal shunt portion may include an outwardly-projecting locating formation for engagement by a suture for suturing the proximal shunt portion to the sclera to hold the proximal shunt portion in place.

The distal shunt comprises a flexible distal tube and the proximal shunt portion comprises a rigid proximal tube, the distal tube and the proximal tube being releasably connected to one another with the lumen of the shunt extending continuously through the distal and proximal tubes.

A spacing between the distal stop formation and the proximal stop formation may be such that opposing sides of the distal stop formation and the proximal stop formation define abutment faces which abut opposite sides of the optic nerve sheath thereby providing for secure location of the shunt relative to the optic nerve sheath.

The shunt may define a fluid flow opening (<NUM>) leading into the lumen at the distal end of the shunt. The distal stop formation may be deformable. More specifically, the distal stop formation may be resiliently compressible.

A distal end of the shunt may be closed, with one or more fluid flow openings (<NUM>) leading into the lumen being defined in a side wall of the shunt near the distal end thereof.

The shunt may incorporate an elutable therapeutic substance. More specifically, the elutable therapeutic substance may be selected from a group consisting of an antibiotic, an anticlotting agent, and an anti-vascular endothelial growth factor.

According to a second aspect of the invention there is provided a shunt system for treating an ocular disorder related to a disorder of intraocular or intracranial pressure in a patient, the shunt system including:.

The distal insertion portion of the shunt inserting device may comprise an elongate hollow shaft defining an internal passageway within which the shunt is slidably received and displaceable.

The distal end of the shunt may be closed, the shunt advancing device including an elongate advancing element having a proximal end and a distal end, the distal end of the advancing element (<NUM>) having a proximal end and a distal end, the distal end of the advancing element being located slidably within the distal insertion portion for abutment with an inner side of the closed distal end of the shunt for exerting a force on the distal end of the shunt for advancing the shunt, the shunt defining at least one fluid flow opening near the distal end extending into the lumen of the shunt for permitting fluid to pass therethrough.

The shunt inserting device may include a housing to which the distal inserting portion is mounted, the shunt advancing device including a hand-operated slider which is slidably mounted to the housing, the slider including an actuator which is engaged with the advancing element for advancing the advancing element and thereby the shunt within the hollow shaft.

The hollow shaft of the distal insertion portion may comprise a lancet (<NUM>,<NUM>) having a taper cut at the distal end thereof defining a discharge opening through which the shunt is advanced.

The taper cut may have a distal end and a proximal end and wherein a distal end region of the taper cut defining the tissue-penetrating tip of the lancet, is sharp-edged while a proximal end region of the taper cut has blunt edges.

The taper cut may be defined by a first bevel cut proximate the proximal end of the taper cut and a second bevel cut proximate the distal end of the taper cut, the sharp-edged distal end region of the taper cut comprising a portion of the second bevel cut and the blunt-edged proximal end region comprising the first bevel cut and a remaining portion of the second bevel cut adjacent the sharp-edged distal end region.

The shunt may have a flexible distal end region and a resiliently compressible, enlarged distal stop formation near the distal end thereof, the distal stop formation being locatable with the subarachnoid space upon implantation of the distal end therein and compressible when received within the internal passageway of the hollow shaft of the distal insertion portion of the shunt inserting device and expandable after passing through the discharge opening of the distal insertion portion, thereby preventing withdrawal of the distal end of the tubular member from the subarachnoid after implantation of the shunt within the subarachnoid space.

The hollow shaft may have an outwardly-projecting stop formation (<NUM>) spaced from the tissue-penetrating tip for preventing over-insertion of the hollow shaft into the subarachnoid space.

The distal insertion portion may comprise an inner lancet (<NUM>) defining the tissue-penetrating tip and a tubular outer support member (<NUM>) which is co-axially disposed relative to the lancet and spaced therefrom so as to define an annular space between the lancet and the outer support member within which the shunt is slidably received and displaceable.

The lancet may have a taper cut at the distal end.

Further features of the invention are described hereinafter by way of a non-limiting example of the invention with reference to and as illustrated in the accompanying diagrammatic drawings. In the drawings:.

With reference to <FIG> of the drawings, a cross-sectional view illustrating anatomical parts of a human eye <NUM> which are required for use in the description which follows below, comprises:.

With reference to <FIG> of the drawings, a shunt as disclosed, is designated generally by the reference numeral <NUM>. The shunt <NUM> is adapted for implantation in the human body so as to provide for flow communication between aqueous fluid in the anterior chamber A of the eye and cerebrospinal fluid in the subarachnoid space B surrounding the optic nerve C. The shunt is adapted for treating ocular disorders related to disorders of intraocular or intracranial pressure in a patient. The shunt <NUM> when implanted, regulates intraocular pressure in the eye of a human patient. For the treatment of glaucoma, the shunt permits aqueous fluid to drain from the anterior chamber of the eye into the subarachnoid space, thereby reducing intraocular pressure. For the treatment of phthisis and idiopathic intracranial hypertension, the shunt permits the flow of cerebrospinal fluid which has a similar composition to aqueous fluid, to flow to the anterior chamber of the eye thereby increasing intraocular pressure.

The shunt <NUM> has an elongate tubular configuration having a proximal end <NUM> and a distal end <NUM>. The shunt defines a lumen <NUM> which extends between the distal and proximal ends.

The shunt <NUM> is of a two-part construction, including a distal shunt portion comprising a flexible distal tube <NUM> of silicone rubber; and a proximal shunt portion comprising a rigid plastics proximal tube <NUM> of polyetheretherketone (PEEK). The rigid proximal tube <NUM> is removably connected to the flexible distal tube <NUM>. This allows the surgeon to assess the function of the shunt and flush the lumen or inject a therapeutic substance through the shunt as required peri- or post-operatively. The distal tube <NUM> defines the distal end <NUM>, while the proximal tube <NUM> defines the proximal end <NUM>. Opposite ends <NUM>, <NUM> of the proximal tube <NUM> and the distal tube <NUM>, respectively, are removably connected. More specifically, the end <NUM> of the proximal tube <NUM> is press-fitted into the end <NUM> of the distal tube <NUM> in an arrangement wherein internal passages of the distal and proximal tubes form a continuous internal passage defining the lumen <NUM>.

The rigidity of the proximal shunt portion facilitates its displacement along a narrow scleral passage which prevents aqueous fluid leakage and prevents tube erosion through conjunctival tissue.

The distal tube <NUM> has an enlarged resiliently compressible distal stop formation <NUM> in the form of an annular flange near the distal end <NUM>. The distal stop formation <NUM> is spaced a predetermined distance from the distal end <NUM>. The distal end <NUM> of the distal tube <NUM> is closed, with two fluid flow openings <NUM>, <NUM> being defined on opposite sides of the distal tube at locations between the distal stop formation <NUM> and the distal end <NUM>.

The shunt further includes an enlarged proximal stop formation <NUM> in the form of an annular flange which is spaced from the distal stop formation a predetermined distance at a position relatively closer to the proximal end of the distal tube.

The distal stop formation <NUM> resists withdrawal of the shunt after implantation of the shunt in the subarachnoid space, while the proximal stop formation <NUM> is disposed externally of the optic nerve sheath upon implantation of the distal end of the shunt in the subarachnoid space for preventing over-migration of the shunt into the subarachnoid space.

The proximal end <NUM> of the shunt is convexly rounded so as to provide the proximal tube with a tapered end facilitating displacement of the proximal tube along the scleral passageway towards the anterior chamber. The proximal tube <NUM> has a curved section <NUM> near the end <NUM> and a straight section <NUM> extending between the curved section and the proximal end <NUM>. The curvature of the curved section conforms to the anatomical curvature of the ocular globe N as is shown in <FIG>, thereby preventing erosion of the surrounding tissue. The straight section <NUM> is displaced along the scleral passageway from about <NUM> away from the corneal limbus to enter the anterior chamber at the trabecular meshwork.

The distal tube is approximately <NUM> in length and has an outer diameter of <NUM> or less. The flexibility of the distal tube allows the distal tube to conform to the anatomical curvature of the ocular globe with minimal resistance. The distal tube may incorporate an elutable therapeutic substance comprising one or more of an antibiotic, an anticlotting agent and an anti-vascular endothelial growth factor.

The proximal tube is approximately <NUM> in length and has an outer diameter of <NUM> or less. The relatively small outer diameter of the proximal tube prevents endothelial decompensation and tube erosion. The proximal tube defines a fluid flow opening <NUM> at the proximal end <NUM>. The opening <NUM> is defined by a central opening at the proximal end <NUM> and a pair of opposed slots <NUM> defined in opposite sides of a wall of the proximal tube at the proximal end <NUM>. These allow fluid to drain into the proximal end opening from multiple axes and prevent tube blockage by iris tissue.

With reference to <FIG>, an embodiment of a proximal tube of the shunt is designated by the reference numeral <NUM>. The proximal tube is similar to the proximal tube <NUM> and, as such, the same and/or similar reference numerals are used in <FIG> to designate features of the proximal tube which are the same and/or similar to features of the proximal tube <NUM>. A first difference is that the proximal tube <NUM> includes three spaced annular ridges <NUM>, <NUM> and <NUM> near the proximal end <NUM> of the proximal tube to resist migration of the proximal tube after implantation in the ocular anterior chamber. A second difference is that the proximal tube <NUM> includes a fenestrated flare <NUM> providing for suturing of the proximal tube <NUM> to the sclera to hold the proximal tube in place.

The invention extends to a shunt system including the shunt <NUM> as claimed and a shunt inserting device <NUM> for implanting the shunt in the subarachnoid space surrounding the optic nerve. The shunt inserting device <NUM> comprises a tubular housing <NUM>, a shunt advancing device <NUM> and a distal inserting portion <NUM> mounted to the housing. The housing <NUM> provides a handle by which the shunt inserting device can be held.

The distal insertion portion <NUM> comprises a lancet <NUM> defining an internal passageway <NUM> within which the distal tube <NUM> of the shunt is slidably located. The lancet has a distal end <NUM> defining a discharge opening <NUM> through which the distal tube is advanced. The distal end <NUM> defines a tissue-penetrating tip <NUM> for penetrating the optic nerve sheath.

The distal end of the lancet is defined by a taper cut. With reference to <FIG> of the drawings, in order to form the taper cut, a first bevel cut <NUM> and a second bevel cut <NUM> is made at the distal end (see <FIG>). The taper cut has a distal end coinciding with the tissue-penetrating tip <NUM> and a proximal end <NUM>. The taper cut is defined by the first bevel cut <NUM> proximate the proximal end <NUM> and the second bevel cut <NUM> proximate the tissue-penetrating tip. The bevel cuts define sharp edges. After making the bevel cuts, the first bevel cut <NUM> and a portion of the second bevel cut <NUM> spaced from the tissue-penetrating tip, are blunted by rounding off sharp edges (see <FIG>) so as to prevent further cutting of tissue and promote maximal stretching, but not tearing, of tissue around the lancet as it is inserted into the optic nerve sheath in order to maximise a seal formed around the lancet by the optic nerve sheath, but also minimise inflammation. The tissue-penetrating tip and a portion of the second bevel cut adjacent the tissue-penetrating tip are not blunted and thus retain their sharp edged properties for cutting through the optic nerve sheath. The blunted regions of the first bevel cut and of a portion of the second bevel cut are designated by the reference letter "B" while the distal end region of the second bevel cut having sharp edges are designated by the reference letter "S" in <FIG>.

The lancet <NUM> has an enlarged stop formation <NUM> in the form of an annular flange at a location spaced a predetermined distance from the tissue-penetrating tip <NUM>. The stop formation <NUM> is configured and dimensioned so as to abut against an external side of the optic nerve sheath thereby preventing over-insertion of the tissue-penetrating tip into the subarachnoid space.

The shunt advancing device <NUM> is configured for advancing the distal tube <NUM> of the shunt distally along the lancet <NUM> for inserting the distal end of the shunt into the subarachnoid space. The mechanism <NUM> includes an elongate advancing stylet <NUM>.

The distal tube <NUM> is received within the internal passageway <NUM> of the lancet <NUM> and the stylet <NUM> is received within the lumen <NUM> of the distal tube. The mechanism <NUM> includes a piston <NUM> which is slidably displaceable along an internal passageway within the housing <NUM>. The mechanism includes a slider block <NUM> at a distal end of the housing which is slidably supported within the housing and a mounting block <NUM> at the distal end which is fixedly mounted to the housing. The lancet <NUM> is fixedly mounted to the mounting block <NUM>. A proximal end of the stylet is connected to the piston, while the slider block defines a passage within which the stylet is slidably located. A sleeve <NUM> is located within the mounting block for supporting the distal tube at its end <NUM>.

The mechanism also include a coil spring <NUM> which is mounted at opposite ends thereof to spigot mounting formations <NUM>, <NUM> of the slider block <NUM> and the piston <NUM>, respectively. The coil spring is compressed when the piston is displaced towards the slider block resulting in the spring exerting a force on the piston <NUM> for urging the piston away from the slider block.

The piston has a resiliently deformable lever arm <NUM> having an engagement projection <NUM> at an end thereof, while the slider block <NUM> has a slider arm <NUM> defining a complementary engagement aperture <NUM> within which the projection <NUM> of the piston is receivable for releasably locking the piston to the slider block.

The housing <NUM> defines an aperture <NUM> at a proximal end region thereof within which the engagement projection of the piston <NUM> is received for releasably locking the piston to the housing in a retracted condition of the piston.

With reference to <FIG>, the shunt is advanced via a manual force applied by a surgeon on the slider block <NUM>. Referring to <FIG>, the shunt is initially wholly received within the lancet <NUM>. The slider block is in a retracted position with the piston <NUM> in an extended position in abutment with the slider block. In this position, the stylet is received within the lumen of the distal tube <NUM>. In order to advance the distal tube distally, the slider block <NUM> is displaced distally by the surgeon as is shown in <FIG>, causing a distal end <NUM> of the stylet to exert a force on an inner side of the closed end of the distal tube, advancing the distal tube distally so that a distal end region of the distal tube projects from the lancet.

The distal stop formation <NUM> of the distal tube <NUM>, being resiliently compressible, is compressed when the distal end of the shunt is received within the lancet. Upon advancement of the distal tube from the lancet, the distal stop formation expands, the outer diameter thereof being relatively larger than the outer diameter of the proximal stop formation <NUM> in its expanded configuration.

After implantation of the distal tube of the shunt into the subarachnoid space, the lancet of the shunt inserting device is retracted leaving the distal tube in its implanted condition. Referring to <FIG>, the engagement projection <NUM> of the piston <NUM> is pushed inwardly causing the piston to be released from its engagement with the slider block thereby causing displacement, under the action of the coil spring, of the piston into its retraction position and thereby withdrawal of the stylet from the distal tube.

With reference to <FIG>, the manner in which the distal tube <NUM> of the shunt <NUM> is implanted in the subarachnoid space, is illustrated, in sequence. A passageway is created through orbital connective tissue surrounding the ocular orbit using an orbital retractor device <NUM>. Once the passageway has been created, the lancet <NUM> of the shunt inserting device is inserted into the orbital retractor with a clear pathway defined to the optic nerve sheath (<FIG>). The tissue-penetrating tip <NUM> of the lancet is inserted through the optic nerve sheath D into the subarachnoid space B. During insertion, the stop formation <NUM> of the lancet abuts against an external side of the optic nerve sheath preventing over-insertion of the lancet (<FIG>). The slider block is displaced distally by the surgeon causing the distal end of the distal tube <NUM> of the shunt to be advanced into the subarachnoid space (<FIG>). The piston <NUM> of the shunt inserting device is thereafter disengaged from the slider block <NUM>, causing retraction of the piston and withdrawal of the stylet <NUM>. Upon withdrawal of the stylet, the support sleeve <NUM> supports the distal tube at its end <NUM> so as to prevent withdrawal of the distal tube along with the stylet. The shunt inserting device is then removed via the orbital retractor leaving the distal end of the distal tube implanted in the subarachnoid space with the remainder of the distal tube extending along a side of the orbital globe.

With reference to <FIG>, the proximal end of the proximal tube is implanted in the anterior chamber of the ocular globe, by initially creating a scleral channel through the sclera using a surgical blade <NUM> which enters the sclera about <NUM> from the limbus and exits the sclera at the trabecular meshwork (<FIG>). Thereafter, the straight section <NUM> of the rigid proximal tube <NUM> is advanced along the scleral channel using forceps <NUM> (<FIG>). After implantation of the proximal end <NUM> in the anterior chamber the opposite end <NUM> of the proximal tube is inserted into the end <NUM> of the distal tube thereby forming the shunt between the anterior chamber and the subarachnoid space (<FIG>).

With reference to Figures <NUM> to <NUM>, an embodiment of a shunt in accordance with the invention, is designated by the reference numeral <NUM>. The shunt <NUM> is similar to the shunt <NUM> with the only difference being that the distal tube has a different configuration at the distal end thereof. The proximal tube of the shunt <NUM> is the same as the proximal tube <NUM> of the shunt <NUM>. In Figures <NUM> to <NUM>, those features of the shunt <NUM> which are the same as and/or similar to those of the shunt <NUM> are designated by the same and/or similar reference numerals.

The shunt <NUM> comprises the rigid proximal tube <NUM> and a flexible distal tube <NUM> to which the proximal tube <NUM> is releasably connected. The distal tube <NUM> comprises an elongate flexible tubular body <NUM> of silicone rubber and a rigid implant body <NUM> of titanium, PEEK or other suitable material.

The rigid implant body <NUM> of the distal tube <NUM> defines a distal end <NUM> of the shunt <NUM>. The distal tube <NUM> is connected to the proximal tube <NUM> at an opposite end <NUM> of the distal tube <NUM>. More specifically, the end <NUM> of the proximal tube <NUM> is press-fitted into the open end <NUM> of the distal tube.

The distal tube <NUM> and the proximal tube <NUM> of the shunt <NUM>, define a lumen <NUM> which extends continuously through the shunt between the distal end <NUM> and the proximal end <NUM> thereof.

The implant body <NUM> comprises a distal stop formation <NUM>, a proximal stop formation <NUM> which is spaced from the distal stop formation and a narrower neck <NUM> which extends between the stop formations. The distal stop formation and the proximal stop formation define inwardly facing abutment faces <NUM> and <NUM>, respectively, which abut inner and outer sides, respectively, of the optic nerve sheath when the distal stop formation <NUM> is implanted in the subarachnoid space as will be explained in more detail hereinbelow. A distal end region of the implant body is tapered towards the distal end <NUM> for facilitating advancement of the distal stop formation through a passageway created in the optic nerve sheath.

The abutment faces <NUM>, <NUM>, are disposed opposite one another and are obliquely slanted so as to conform to the curvature of inner and outer surfaces of the optic nerve sheath following implantation.

The invention extends to a shunt system including the shunt <NUM> and a shunt inserting device <NUM> for implanting the distal tube <NUM> in the subarachnoid space.

The shunt inserting device <NUM> comprises a tubular housing <NUM> and a distal inserting portion <NUM> mounted to the housing. The tubular housing provides a handle by which the shunt inserting device can be held.

The distal inserting portion includes an inner lancet <NUM> defining an internal passageway <NUM>. The lancet has a distal end <NUM> which is identical to the distal end <NUM> of the shunt inserting device <NUM>. As such, the lancet defines a tissue-penetrating tip <NUM> at the distal end for penetrating the optic nerve sheath for defining a passage therethrough through which the distal end of the implant body <NUM> can pass. The distal inserting portion further includes a tubular outer sleeve <NUM> within which the lancet is located in a spaced arrangement wherein the lancet and the outer sleeve are co-axially arranged and define an annular space <NUM> within which the tubular body <NUM> of the distal tube <NUM> is displaceably received.

The lancet <NUM> extends into the housing to a location at a proximal end region of the housing. The housing defines an inlet port <NUM> at a proximal end <NUM> thereof which is in fluid flow communication with the passageway <NUM> of the lancet, to which an outlet of a syringe <NUM> or the like, containing a gas or a liquid, can be connected.

Claim 1:
A shunt (<NUM>, <NUM>) for treating an ocular disorder related to a disorder of intraocular or intracranial pressure by regulating intraocular pressure in an eye of a patient, the shunt comprising
a proximal shunt portion defining a proximal end (<NUM>, <NUM>) which is implantable in an ocular anterior chamber (A) of a patient and a distal shunt portion defining a distal end (<NUM>, <NUM>) which is implantable in a subarachnoid space (B) of the patient, the shunt defining a lumen (<NUM>, <NUM>) extending longitudinally between the distal and proximal ends, the shunt having an enlarged distal stop formation (<NUM>, <NUM>) near the distal end of the shunt, which is disposed in the subarachnoid space after implantation of a distal end region of the shunt in the subarachnoid space, for resisting withdrawal of the shunt after implantation in the subarachnoid space, and being flexible along a portion of a length of the shunt so as to conform to an outer anatomical curvature of the ocular globe (N),
characterized in that the proximal shunt portion includes at least one outwardly-projecting ridge formation (<NUM>) for resisting migration of the proximal shunt portion after implantation thereof in the ocular anterior chamber, and
wherein the distal shunt portion comprising a flexible distal tube and the proximal shunt portion comprising a rigid proximal tube are releasably connected to one another with the lumen of the shunt extending continuously through the distal and proximal shunt portions.