Intraocular glaucoma drainage device implant

Abstract

An intraocular drainage device for implantation in an eye. It includes a base plate, a drainage tube, and a primary drainage region. The drainage tube is adapted to allow for fluid flow from the anterior or posterior chamber of the eye to the primary drainage region. The inner diameter of the drainage tube is optimized for a chosen length of the drainage tube so as to achieve an intraluminal pressure differential in the range of about 5-10mmHg to reduce intraluminal flow.

Description

INTRAOCULAR GLAUCOMA DRAINAGE DEVICE IMPLANTFIELD OF THE INVENTION

[0001] The present invention generally relates to devices to reduce intraocular pressure (IOP), in particular, to an intraocular glaucoma drainage device implant comprising a drainage tube with an optimized inner diameter and length, thereby allowing for an intraluminal pressure differential sufficient to provide flow restriction or mitigate the incidence of postoperative hypotony while reducing the overall IOP to a targeted level.PRIOR ART

[0002] The contents of related patent US 7,776,002 B2 is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION

[0003] Glaucoma is a progressive optic neuropathy that ultimately leads to vision loss in one or both eyes.

[0004] Elevated IOP is one of a handful of risk factors that accounts for the development and progression of the disease. A major cause of elevated IOP is resistance to the outflow of aqueous humour, often occurring in the trabecular meshwork.

[0005] Existing procedures to treat glaucoma seek to bypass the physiologic outflow pathway and move the aqueous humor that fills the eye directly to the surface of the eye.

[0006] Glaucoma Drainage Devices (GDD) seek to reduce IOP within the eye and maintain long-term IOP at normal levels. They operate by shunting fluid from the anterior chamber of the eye to a reservoir located on the surface of the eye in the equatorial region.

[0007] Modem GDDs often consist of a silicone tube connected to an endplate made of polypropylene or silicone. These tubes commonly have an internal and external diameter of 0.30 mm and 0.64 mm respectively. The endplate is secured to the sclera of the eye, and covered by two layers of tissue.

[0008] A fibrous capsule develops around the endplate, and is responsible for providing resistance to outflow (for non-valved implants), and aids in determining the final IOP.

[0009] Aqueous humor often collects in the space between the end plate and surrounding capsules, which then passively diffuse through the capsule wall into periocular capillaries and lymphatics.

[0010] Non-valved implants do not have an active flow restriction mechanism, and therefore need to be initially closed (either ligated with a polyglactin suture or stented with a non-absorbable suture) to allow sufficient time for encapsulation, often 4-6 weeks. Without a complete capsule, fluid may escape resulting in decompensation of the eye.

[0011] In contrast, valved implants do not rely on capsule formation to prevent early hypotony. Their flow restricting valve mechanism allows them to function only at specific ranges of IOP and helps prevent low IOP in the early postoperative period. However, these implants often have a smaller endplate surface area, and can be more prone to scarring, resulting in higher lOPs. However, because of the pressure drop associated with the valve they do not offer a low enough pressure drop for the long term so tend to fail early.

[0012] For both valved and non-valved implants, their associated surgical procedures are largely the same. A surgeon makes an incision in the conjunctive of the eye, and creates an opening in one of the four quadrants of the eye for implantation of the GDD.

[0013] The proximal end of the drainage tube is placed through a tunneled track into the anterior chamber of the eye. The distal end is connected to the endplate which is sutured through the sclera, usually 8-10 mm from where the tube is inserted. The tube is typically covered with a patch graft to prevent erosion through the superficial tissue.

[0014] Postoperative complications often arise following implantation of GDDs. Surgeons need to ultimately balance the risks and benefits of the procedure, as a significant reduction in IOP below approximately 6 mmHg carries a greater risk of potential vision loss. In procedures involving implanting GDDs, mitigating hypotony (IOP in the range between 2- 6 mmHg) and hypotony related complications is key to long-term success of the procedure.

[0015] If not appropriately mitigated, hypotony may lead to sight-threatening complications, including comeal decompensation and hypotony induced maculopathy.

[0016] Randomized clinical trials have demonstrated that non-valved implants with larger endplates result in lower final lOPs, but carry a greater risk of hypotony-related complications. With non-valved implants, hypotony may occur at various timepoints if the surgeon doesn’t take adequate precautions to control the aqueous outflow prior to the formation of the bleb. To maintain adequate control of IOP while a temporary ligature is in place, slits or fenestrations are commonly made in the tube to allow for aqueous flow. This technique, though commonly employed, is unpredictable. In the weeks that follow a procedure, the temporary ligature may release, often resulting in a precipitous drop in IOP as aqueous humor fills the empty space surrounding the endplate. Finally, as patients age, aqueous product can decrease and, at times, hypotony can occur due to over filtration into the reservoir. Valved implants, on the other hand, tend to protect against short-term and long-term hypotony, but do not provide the same level of control over IOP, thus limiting their overall utility because of their inherent characteristics are prone to fail early

[0017] It is an aspect of the present invention to overcome or ameliorate the problems of the prior art by providing an improved intraocular glaucoma drainage device implant.SUMMARY OF THE INVENTION

[0018] In a first aspect the invention comprises an intraocular drainage device for implantation in an eye, comprising: abase plate, a drainage tube, and a primary drainage region; wherein the drainage tube is adapted to allow for fluid flow from the anterior or posterior chamber of the eye to the primary drainage region; wherein the inner diameter of the drainage tube is optimized for a chosen length of the drainage tube so as to achieve an intraluminal pressure differential in the range of 5-10 mmHg and thus reduce intraluminal flow below such intraocular pressure.

[0019] In an embodiment, the drainage tube comprises a visual indicator to ascertain the pressure differentials at sections along the length of the tube

[0020] In an embodiment, the device further comprises a secondary drainage region, wherein the secondary drainage region is adapted to receive fluid outflow from the primary drainage region.

[0021] In an embodiment of the device, the optimized inner diameter of the tube is determined from Poiseuille’s Law.

[0022] In an embodiment, the device is made from polypropylene.

[0023] In an embodiment, the drainage tube is constructed from silicone.

[0024] In an embodiment, the visual indicator is designed to visually denote theoretical pressure differentials between 5 mmHg to 10 mmHg.

[0025] In an embodiment, the drainage tube comprises a pressure regulation capability to allow for aqueous humor to drain through the tube when intraocular pressure exceeds a predetermined threshold.

[0026] In an embodiment, the pressure regulation capability is a valve.

[0027] In an embodiment, the predetermined intraocular pressure threshold is 6 mmHg.

[0028] It should be noted that any one of the aspects mentioned above may include any of the features of any of the other aspects mentioned above and may include any of the features of any of the embodiments described below as appropriate.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows.

[0030] Figure 1 is a side cross-sectional view of an eye with the device implanted;

[0031] Figure 2 is a perspective view of the device; and

[0032] Figure 3 is another perspective view of the device.DETAILED DESCRIPTION OF THE INVENTION

[0033] The following detailed description of the invention refers to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts. Dimensions of certain parts shown in the drawings may have been modified and / or exaggerated for thepurposes of clarity or illustration.

[0034] The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments can be utilized, and other changes can be made, without departing from the spirit or scope of the subject matter presented herein.

[0035] As used herein, the term “about” in the context of concentrations of components, conditions, measurement or calculated values, etc., means+ / -10% of the stated value, for instance, + / -5% of the stated value, or + / -4% of the stated value, or + / -3% of the stated value, or + / -2% of the stated value, or + / -1% of the stated value, or + / - 0.5 % of the stated value, or + / — 0% of the stated value.

[0036] The disclosure relates to a glaucoma drainage device (GDD), or implant, having an improved design over presently available GDDs. The device comprises a tube with an optimized inner diameter, allowing for a pressure differential of about 6 mmHg. For example, and explained further in the following description, a device with a tube length of 12 mm would have an associated optimal tube inner diameter of about 65 pm, resulting in significant reduction in the incidence of postoperative hypotony while allowing for more predictable IOP control during the early postoperative period. There is no need for occlusion of the tube, as the length and associated diameter will sufficiently restrict flow.

[0037] The embodiments described are structured in a manner that (a) greatly facilitates ease of implementation and manipulation during an implant procedure; (b) greatly facilitates maintenance of post-operative anterior chamber stability; (c) nearly or essentially eliminates post-operative complications such as hypotony; and (d) reduces or minimizes complications typically associated with implantation in shallow anterior chambers, and hence is suitable for use in such situations.

[0038] Such devices may be surgically implanted between the sclera and the conjunctiva of the eye, thereby allowing fluid such as aqueous humor flows to flow through the device through a fluid channel and exiting from an outlet port.

[0039] Referring now to the Figures, the present invention relates to an intraocular glaucoma drainage device implant 1 that allows for optimizing the inner diameter of a drainage tube 3 to a size facilitating a desired pressure differential of about 6 mmHg. Such adevice results in a significant reduction in the incidence of postoperative hypotony.

[0040] The intraocular drainage device 1 comprises a base plate 2 shaped to fit the curvature of an eye, when implanted; and a drainage tube 3 coupled to the plate, the drainage tube 3 leading to a primary drainage region 4 and second drainage region 8.

[0041] The device 1 comprises a ridge 6 on the upper surface of plate 2, the ridge 6 defines the primary drainage region 4, into which fluid from the anterior or posterior chamber of the eye can be drained through when in use. A boundary structure 7 is located on the perimeter of the upper surface of plate 2. The height of ridge 6, relative to the surface of plate 2, is higher than boundary structure 7.

[0042] There is a secondary drainage region 8, defined between inner ridge 6 and boundary structure 7, into which fluid from the primary drainage region 4 may be received when device 1 is in use. When the pressure of fluid in the primary drainage region 4. builds, fluid spills into the secondary drainage region 8. A hole 5 located on inner ridge 6 has a diameter enabling drainage tube 3 to drain fluid from the anterior or posterior chamber of the eye to the primary drainage region 4.

[0043] The drainage tube 3, comprises a proximal end and a distal end. The distal end is configured to be placed beneath the tissue of the eye and the proximal end to be placed in the anterior chamber. Drainage tube 3 drains aqueous humor from the anterior chamber of the eye, with the pressure gradient of the tube 3 controlling the flow of aqueous humor through the tube.

[0044] In an embodiment, the drainage tube 3 may comprise a passageway therethrough for drainage of aqueous humor from the anterior chamber to the sclera. Tube 3 may also additionally comprise pressure regulation capabilities, such as valves, which allows for aqueous humor to drain through the tube 3 when intraocular pressure exceeds a predetermined threshold.

[0045] The plate 2 is curved in line with the curvature of the eye. The plate 2 preferably comprises holes near the outer perimeter of the plate, allowing for sutures to be threaded through for the purpose of securing the implanted plate 2 to the surface of the eye.

[0046] The device 1 may be positioned in any of the four quadrants of the eye. Mostcommonly, the superotemporal and inferonasal quadrants are used.

[0047] The drainage tube 3 may have visibly denoted sections which correlate to a theoretical pressure differential of the tubular portion ranging between about 5 mmHg to 10 mmHg. The drainage tube 3 may have these sections laser marked, colored, or otherwise visually identifiable allowing for surgeons to select where to cut the tube to retain the hypotony mitigating pressure gradient.

[0048] The device 1 may be made from any rigid of flexible biocompatible material, such as but not limited to polypropylene or silicone.

[0049] The casing of drainage tube 3, defining an opening that allows for fluid to enter into a lumen or cavity of the tube 3, may be constructed from a range of materials. In a preferred embodiment, the casing is silicone.

[0050] The intraocular drainage device 1 is designed per the principles of fluid dynamics to mitigate the risk of hypotony in the postoperative period.

[0051] The Hagen-Poiseuille equation, also referred to as Poiseuille’s Law, is useful in determining the vascular resistance and hence flow rate of intravenous (IV) fluids for different sized peripheral and central cannulas.

[0052] Poiseuille’s Law describes that gives the pressure drop in an incompressible and Newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant cross section, provided below.

[0053] It is known in the art that Q refers to volumetric flow rate, D refers to the diameter of the cylindrical pipe, T| the dynamic viscosity of the fluid, L the length of the pipe, and AP the pressure drop.

[0054] This can be arranged to obtain the required diameter to achieve a desired pressure differential.

[0055] Using a desired pressure differential AP = 6 mmHg ~ 800 Pa being the target intraocular pressure floor, the ideal inner diameter of a glaucoma drainage device with drainage tube 3 length of about 12 mm is determined. The median flow rate of aqueous humor in the eye is approximately Q = 4.167* 10"11m3 / s « 2.5 pL / min. The dynamic viscosity of aqueous humor is approximately q = 8.9* W4Pa.s at 25° and about q = 6.9* 10‘4Pa.s at 37°, being about the dynamic viscosity of water.

[0056] The resultant ideal diameter D is about 65 pm. However, it is to be understood that the calculation may be repeated for tube 3 ranges between about 6 mm - 18 mm to determine the ideal tube diameter associated with a desired length.

[0057] The diameter of the tube 3 may increase in size to its original diameter and / or final diameter thereby influencing the rate of fluid exiting the eye by allowing for an increase in fluid flow.EXAMPLE 1

[0058] Optimal values have been calculated for the ideal (inner) diameter of the tube at lengths between about 6 mm - 18 mm. Table 1 below provides the calculated values.Table 1 (q = 6.9x lO-4Pa.s at 37°)

[0059] The reader will now appreciate the present invention which provides an ophthalmic surgical instrument and a method of use of said instrument in treating glaucoma.

[0060] While the invention has been described with reference to specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications and applications may occur to those who are skilled in the art, without departing from the true spirit and scope of the invention as described by the appended claims.LIST OF COMPONENTS

[0061] The drawings include the following integers:1 intraocular glaucoma drainage device implant2 base plate3 drainage tube4 primary drainage region5 hole6 inner ridge7 boundary structure8 secondary drainage region

[0062] Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus. Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in this field.

[0063] In the present specification and claims (if any), the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers.

Claims

CLAIMS1. An intraocular drainage device for implantation in an eye, comprising: a base plate, a drainage tube, and a primary drainage region; wherein the drainage tube is adapted to allow for fluid flow from the anterior or posterior chamber of the eye to the primary drainage region; wherein the inner diameter of the drainage tube is optimized for a chosen length of the drainage tube so as to achieve an intraluminal pressure differential in the range of about 5-10mmHg to reduce intraluminal flow.

2. The device of claim 1, wherein the drainage tube comprises a visual indicator to ascertain the pressure differentials at sections along the length of the tube.

3. The device of claim 1, further comprising a secondary drainage region, wherein the secondary drainage region is adapted to receive fluid outflow from the primary drainage region.

4. The device of claim 1, wherein the optimized inner diameter of the tube is determined from Poiseuille’s Law.

5. The device of claim 1, wherein the inner diameter of the drainage tube is between about 50 and 75 pm, and the length of the drainage tube is between about 6 mm and 20 mm.

6. The device of claim 5, wherein the inner diameter of the drainage tube is about 65 pm, and the length of the drainage tube is about 12 mm.

7. The device of claim 1, wherein the length of the drainage tube is about 10 mm.

8. The device of claim 1, wherein the length of the drainage tube is about 12 mm.

9. The device of claim 1, wherein the length of the drainage tube is about 14 mm.

10. The device of claim 1, wherein the device is made from one of or a combination of biocompatible, materials for example but not limited to: polypropylene, silicone andpolyimide.

11. The device of claim 2, wherein the visual indicator is adapted to ascertain pressure differentials between about 5 mmHg to 10 mmHg.

12. The device of claim 1, wherein the drainage tube comprises a pressure regulation capability to allow for aqueous humor to drain through the tube when intraocular pressure exceeds a predetermined threshold.

13. The device of claim 12, wherein the pressure regulation capability is a valve.

14. The device of claims 12, wherein the predetermined intraocular pressure threshold is about 6 mmHg.

15. An intraocular drainage device for implantation in an eye, comprising: a base plate, a drainage tube, and a primary drainage region; wherein the drainage tube is adapted to allow for fluid flow from the anterior or posterior chamber of the eye to the primary drainage region; wherein the inner diameter of the drainage tube is optimized for a chosen length of the drainage tube so as to achieve an intraluminal pressure differential in the range of about 5-10mmHg to reduce intraluminal flow.Wherein the drainage tube is occluded to prevent intraluminal flow.

16. The Device of claim 15, where in the occlusion is caused by a suture.

17. The Device of claim 16, where in the suture is dissolvable.

18. The Device of claim 15, where in the occlusion is caused by a dissolvable solid plug.

19. An intraocular drainage device for implantation in an eye, comprising: a base plate, a drainage tube, and a primary drainage region; wherein the drainage tube is adapted to allow for fluid flow from the anterior or posterior chamber of the eye to the primary drainage region; wherein the inner diameter of the drainage tube is partially occluded and optimized for a chosen length of the drainage tube so as to achieve an intraluminalpressure differential in the range of about 5-10mmHg to reduce intraluminal flow.

20. The Device of claim 19, where in the partial occlusion is caused by a dissolvable material

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