Background
Presbyopia is a vision disorder caused by a disorder of the accommodation mechanism of the eye associated with aging. The accommodative mechanism is primarily regulated by parasympathetic innervation of the ciliary smooth muscle. In non-presbyopia, this causes the muscles to slide forward in a combined manner and produces inward movement of the muscles. The result is a reduction in the diameter of the ciliary muscle ring that can cause a series of events that result in a clear view of nearby objects.
Presbyopia is most commonly treated by the use of aged, bifocals and progressive multifocal contact lenses. However, the inconvenience associated with eyeglasses and contact lenses has prompted research and development into surgical techniques directed to correcting presbyopia.
Glaucoma, and more particularly primary open angle glaucoma, is an ocular disease in which the optic nerve is progressively damaged, producing defects of some character in the patient's peripheral vision. Primary open angle glaucoma occurs when the drainage canals of the eye become clogged over time, resulting in a gradual and irreversible loss of vision. Glaucoma is usually treated with eye drops, such as PILOCARPINE (PILOCARPINE), propyne (PROPINE), TIMOLOL (TIMOLOL) and XALATAN (XALATAN), which have side effects. Oral administration may also be used for treatment.
Methods for treating presbyopia and glaucoma and scleral clips for use in such methods are disclosed in my U.S. patent No.6,517,555 and U.S. published application No. us2004/0092968, both of which are incorporated herein by reference. The method includes applying a plurality of clips to the sclera under the conjunctiva. In the treatment of presbyopia, the clips function to support or reinforce the ciliary muscles so that they can operate to alter the lens diameter for focusing on nearby objects. In the treatment of glaucoma, the tensioning of the sclera with the clip tensions the ocular tissue that provides drainage, thereby reducing the obstruction of the drainage canal and facilitating drainage of fluid from the eye.
While the clips disclosed in my aforementioned referenced patents and applications were designed for use in the methods described herein, the development process has indicated a need for improved clips that (a) are easier to use, (b) grip the sclera more stably, and (c) are less contoured, thereby making them more comfortable to wear.
Accordingly, it is an object of the present invention to provide an improved clip and a method for applying the clip to an eye that is uniquely suited for treating presbyopia and/or glaucoma.
Detailed Description
The method of using the clip of the present invention is based on the theory that presbyopia is due to the barrier of the ciliary body to adjust the lens diameter to focus an image of a nearby object onto the retina. The ciliary muscle changes the lens diameter by using the sclera as a supporting or fixation structure. As the sclera of the eye weakens due to age, the ciliary muscles lack the support required to change the lens diameter to focus on nearby objects. Thus, in order for the ciliary muscle to change the lens diameter to see nearby objects, the sclera must be supported or reinforced. Accordingly, an improved clip for strengthening the sclera is provided to provide a stronger and more stable support for the ciliary muscle. The clip of the present invention accomplishes this by compressing or compressing the sclera. In effect, the sclera is strengthened and then the ciliary muscles can again function to provide adequate near vision.
It is believed that the method and its associated clip may also be advantageously used to treat open angle glaucoma. Similar to presbyopia, glaucoma is an age-related disease and is caused by the accumulation of fluid pressure in the eye that damages the optic nerve. Over time, glaucoma destroys peripheral vision, thereby narrowing the visual field. In a healthy eye, fluid produced by the ciliary tissue surrounding the lens drains from the eye through a series of drainage canals around the outer edge of the iris. With age, due to the lack of support of the ciliary muscles, they are unable to keep these drainage ducts open to allow free drainage of fluid. By supporting the sclera with the clips disclosed herein and in accordance with the present methods, support is provided for the ciliary muscles and the eye tissue providing drainage is tightened, thereby reducing blockage of the fluid drainage canals and facilitating drainage of fluid from the eye.
Referring to fig. 1, a simplified cross-sectional view of a human eye 10 having a lens 12 contained within a lens capsule 14 is seen. The ciliary body and ciliary muscles 16 are connected to the lens capsule 14 and also to the choroid 18. The sclera 20 overlies the choroid 18 and in front of the eye overlies the ciliary muscle 16 and terminates in a scleral spur 22 in the cornea 24 of the eye. The conjunctiva 26 surrounds the cornea 24 and overlies a globular sheath (or Tenon's capsule) 28, which in turn overlies the sclera 20 in front of the eye 10. Blood is supplied to the sclera by arteries in the superior, inferior, medial and lateral rectus muscles 30, 32, 34 and 36, respectively, as best seen in fig. 2.
An improved clip, generally indicated at 40, for use with the sclera is shown in fig. 3-6. The clip, generally designated 40, includes a body portion 42 with two opposed feet 44 extending from opposite ends of the body. It should be understood that the clip 40 should not irritate or damage the sharp edges of the tissue it contacts.
In practice, the length of body 42 may vary between about 3.5mm-6.0mm based on the desired degree of compression of the sclera. Shorter clips are used where less compression is indicated, most likely in younger patients. Conversely, where greater compression is indicated, and likely in the case of older patients, longer clips are used. It should be understood that the length of the body 42 also generally defines the working length of the clip. The body 42 has a width of about 1.0mm to 2.5mm and a thickness of about 600 μm to 2.00 mm.
The opposing feet 44 are generally L-shaped (as shown in FIG. 4), with the free end of the long leg 46 of the L having a curved or semi-circular shape (as best seen in FIGS. 3 and 6) to reduce the likelihood of damage to the tissue contacted by the feet. These curved ends are adapted to be received in pockets made in the scleral surface, as described in more detail below.
The foot 44 has a working length of about 200 μm, as defined by the long leg 46 of the L-shape. The short leg 48 of the L-shape is adjusted between about 100 μm long to 200 μm long. Thus, the overall length of the clip 40 is the sum of the length of the two feet 44 and the length of the body 42, and thus ranges from about 4.0mm to 6.5 mm.
In accordance with one aspect of the invention, the body 42 of the clip 40 is formed with a reverse curvature (i.e., the body curves downward) such that when the clip 40 is applied to the eye, the clip 40 pushes or presses down on the sclera, thereby additionally deforming the sclera. Alternatively, the central portion of the body 42 of the clip 40 may be thicker than the end portions to achieve the same effect. The amount of reverse flexion is generally the same as the length of the leg 48 of the foot 44, i.e., from 100 μm to 200 μm, but may be more or less depending on the amount of scleral compression desired.
The reverse flexion applies an inward force to aid in the lack of contraction of the aging ciliary body, thereby providing GeorgeNamed m.d.) "Wedge effect ". More specifically, the pressure created by the reverse flexure pushes the ciliary muscle inward and forward, changing the position of the ciliary processes and the location of the zonular plexus, thereby releasing the tension of the zonules and providing deformation of the lens by moving the lens forward and increasing its anterior flexure. This may result in enhanced lens function, resulting in lens accommodation. Alternatively, the clip body may be enlarged in the central region between the points to provide the same effect.
The clip 40 may be made from a variety of suitable biocompatible materials, including titanium and Polymethylmethacrylate (PMMA). Preferably, the entire clip is molded from PMMA. Alternatively, the body 42 of the clip 40 may be molded from PMMA, while the feet 44 are made from titanium. The titanium foot 44 is secured to the body 42 by overmolding the body with the foot 44 in situ such that the molten PMMA flows around the securing leg 50 which extends from the short leg 48 of the foot 44. The length of the fixing leg 50 may be up to 500 μm to ensure that sufficient length is received in the body 42 to maintain structural integrity. The clip may also be coated with a suitable bioactive material, such as sytostatic drugs, which have anti-inflammatory properties.
Turning to fig. 7-9, an ophthalmic clip 40 according to another embodiment of the present invention is shown. The clip is similar to the clip shown in figures 3-6 except for the dimensions, and the same reference numerals are used. Referring to fig. 7-9, body 42 has a length that may vary from about 2.0mm to 5.0mm (preferably about 2.5mm), depending on the desired degree of scleral compression. The clip 40 has a width of about 1.0mm to 2.5mm (preferably about 1.0mm) and a thickness of about 200 μm to 1.00mm (preferably about 250 μm).
The opposing feet 44 are generally L-shaped (as shown in fig. 8), with the free end of the long leg 46 of the L having a curved or semi-circular shape (as best seen in fig. 7 and 9) to reduce the likelihood of damage to the tissue contacted by the feet. These curved ends are adapted to be received in pockets made in the surface of the sclera, as described in more detail below.
The feet 44 have a working length of about 1.5mm to about 2.5mm (preferably about 2.5mm), as defined by the long leg 46 of the L-shape, and a longer length to help retain the clip in the pocket of the sclera. The short leg 48 of the L-shape is adjusted between about 800 μm long to 1.5mm long, and preferably is about 800 μm long. Thus, the overall length of the clip 40 is about 5.0mm to 7.5 mm.
The body 42 of the clip 40 is formed with a reverse bend (i.e., the body bends downward) so that when the clip 40 is applied to the eye, the clip 40 pushes or presses down on the sclera, thereby additionally deforming the sclera. In practice, the reverse bend has a bend radius of from 6.0mm to about 9.0mm, preferably about 7.5 mm.
Referring to fig. 10-12, a third embodiment of a clip 54 according to the present invention is shown. The clip 54 is the same as that shown in figures 7-9 and corresponding structure is given the same reference numerals. As shown in fig. 10-12, the clip 54 includes an additional foot 56 extending from each end of the body and positioned above the feet 46 to define a space 58 between the additional foot 56 and the feet 46. The space 58 is adapted to receive therein a portion of the sclera defined by the incision for making the pocket 52 for receiving the foot 46 and the surface of the sclera, the space ranging between about 300 and 400 μm. When applied to the sclera, the feet 46, 56 grasp the sclera therebetween to help hold the clip in place.
The clip may include other features that help ensure that the foot is retained in the pocket made by the sclera. Referring to fig. 13, a fourth clip embodiment is shown, generally designated 60. The clip 60 comprises two parts 62, 64. The first member 62 is similar to the clip 40 shown in fig. 7-9. The second part 64 overlies the first part 62 and includes a series of retaining pegs (3 shown) 66a, b, c which are received in cooperating pegs 68a, b, c in the foot and body of the first part 62. When the feet of the first clip portion are received in pockets made in the sclera, a "pinhole" is made in the pocket through which the retaining pegs 66a, 66c are positioned to be inserted into the holes 64a, 64c to secure the clip 60 firmly to the sclera. The central peg 66b on the second part 64 and the hole 68b on the first part 62 help properly position and align the two parts of the clip 60 during their assembly and application to the eye.
Figure 14 shows another alternative of a clip generally designated 70. The clip 70 is generally similar to that shown in fig. 7-9, but includes a central aperture 72 in the body portion of the clip through which a "screw" or other fastener 74 is received. The screw 74 has a point that, when inserted into the central aperture 72, bites into the sclera to a depth of, for example, about 100 μm to secure the clip 70 to the sclera. For example, the threaded shank of the screw 74 may include, for example, threads or hooks to secure the clip to the sclera.
Referring to fig. 15, there is shown another embodiment of a clip, generally designated 80, which also has means for ensuring that the clip is held in place on the sclera. The clip 80 is similar to the clip shown in fig. 7-9 except that each foot has at least one aperture 82 therein through which ciliary tissue will grow upon application of the clip 80 as part of the healing response to the incision making the pockets for receiving the feet of the clip. Thus, the tissue growing through the holes 82 acts to hold the clip in place in the eye.
A method of applying the clip of the present invention to an eye will now be described. First, the eyelid is held open using a lid expander and a local anesthetic, such as subconjunctival lidocaine, is applied to the eye. The location of the ciliary body is then determined by using commercially available ultrasound equipment. Referring to fig. 2, an incision 38 is then made in the conjunctiva parallel to the scleral limbus (scleral-limbal) junction to dissect the conjunctiva around tenon's capsule 28. The incision is then made deep into the outer layer of the sclera. The incision is opened and the tenon's capsule is moved laterally to expose the sclera 20 if necessary. Opposing pockets 52 are made on the surface of the sclera to receive the opposing legs of the clip using preset markings. The openings of the pockets may be spaced about 3.5-6.0mm apart depending on the length of the clip body and have a depth (in a direction generally parallel or concentric to the scleral surface) corresponding to the length of the foot, i.e., about 200 μm to 2.5 mm. The pocket extends from the surface of the sclera no deeper than about 50% of the sclera thickness into the sclera, i.e., no deeper than about 350 μm, preferably no deeper than about 200 μm.
The clip is then loaded onto an application tool which simply comprises a grasping forceps which grasps the short leg of the foot to apply axial pressure to the clip along the clip body, thereby bending the body and moving the feet toward each other. The foot is then introduced into a pocket 52 made in the sclera. If the clip 54 according to fig. 10-12 is used, the portion of the sclera between the incision for the pocket 52 and the scleral surface is received in the space 58 between the feet 46 and 56. If a clip according to fig. 13 is used, additional pin holes are made in the pocket to receive the pegs 66a, 66 c. Once the holes are made in the bag, the second part of the clip 62 is assembled to the first part 62 of the clip. Using the clip 70 according to fig. 14, a screw 74 is inserted into the hole 72 and manipulated so that its point bites into the sclera.
The clip applied has a generally low profile, closely fitting to the curvature of the eye, providing reinforcement to the sclera. The tenon's capsule 28 is then replaced tightly over the clip and conjunctiva. No suturing is required as the conjunctiva self seals. Preferably, a fibrin adhesive, such as Tisseel VH fibrin sealant available from Baxter Healthcare, Inc., may be applied over the tight connection to accelerate healing. The process is then repeated for each of the 4 quadrants according to the actual needs of the surgeon so that the clips are applied equally to the eye with respect to the corneal 24 spacing between adjacent rectus muscles. The ointment was applied to the eye, which was then subjected to 24 hour repair.
It will be readily appreciated that this procedure can be simply reversed by merely again treating the sclera by making an incision in the conjunctiva over the clip, moving the tenon's capsule to expose the clip, and then removing the clip.
The application of each clip should deform the uvea and move the sclera inward by about 0.5mm, and if 4 clips are applied, by 2mm overall. This will increase the amplitude of accommodation, thereby reversing the presbyopic effect. The inward movement of the sclera should also increase the angle of schlemn's canal (canals of schlemn) to increase fluid flow and reduce intraocular pressure to improve the glaucoma effect.
Thus, a method and a clip for carrying out the method have been provided that fully meet the objects of the present invention. While the present invention has been described in terms of preferred ophthalmic clips and methods, it is not intended that this limit the invention thereto. Indeed, the clip may be applied to medical procedures other than those described above. Accordingly, the invention is to be defined by the scope of the following claims.