The present invention relates to an apparatus, use and method that maintains a preoperative position of the posterior lens capsule during and after cataract removal and insertion of a lens implant.
A lens haptic conventionally is configured to either be in the plane of the lens optic or to encounter the plane of the lens optic at an angle of 10 degrees or less. The purpose for the lens haptic is to attain stable lens fixation.
The present inventor, an experienced surgeon who has performed tens of thousands of cataract operations, was quoted in the May 2004 edition of Ophthalmology Management as follows with respect to Cataract Surgery: Managing Weak Zonules and an anterior capsule support system bearing his name is described. Such an anterior capsule support system is described in U.S. Pat. No. 6,183,480 by the same inventor.
The Anterior Chamber Lens Option: Richard J. Mackool, M.D., director of The Mackool Eye Institute and Laser Center in Astoria, N.Y., and senior attending surgeon at the New York Eye and Ear Infirmary, notes that being able to put an IOL intraocular lens) in the bag with the endocapsular ring doesn't mean you always should. “When you know that a weak zonule could lead to eventual dislocation of the capsular bag and its IOL,” Dr. Mackool says, “consider placing an endocapsular ring in the bag to establish a (hopefully) permanent position for the capsule—but implant an anterior chamber lens instead of placing the IOL in the bag or sulcus. The capsule will separate the anterior and posterior segments, reducing the likelihood of macular edema and vitreoretinal complications; meanwhile, the anterior chamber lens will remain perfectly fixated.”
The Mackool Cataract Support System. A capsular tension ring may not hold the bag in place during phaco if the zonule is especially weak. Surgeons sometimes use iris retractors on the rim of the capsulorhexis to try to manage this problem, but iris retractors aren't designed for this purpose; their hooks have a short return, and if the retractor comes in at an angle, the hook is not in the plane of the rim you're trying to grab.
In contrast, the Cataract Support System designed by Richard Mackool, M.D., has a hook return of 2.5 mm, and the hook is angled to be in the plane of the anterior capsule. As a result, it's easy to get a firm and reliable grip on the rim. An endocapsular ring can be inserted before the Cataract Support System is removed.
The Mackool system: maintains the position of the capsule during phaco; supports the fornix as well as the capsulorhexis rim so the peripheral capsule isn't attracted toward the phaco tip; avoids the problem of the endocapsular ring trapping cortex; prevents zonular stress during nuclear rotation; makes it possible to perform posterior chamber phaco even with dislocated cataracts having almost no zonular support.
Conventional intraocular lenses have angulated attachments, otherwise known as haptics, but their purpose is to keep the body of the lens implant, also known as the lens optic, away from the iris. Such conventional intraocular lenses with haptics attachment, however, are not designed to keep the posterior lens capsule from undergoing a forward (anterior) shift after cataract surgery.
The present inventor recognizes that the forward (anterior) shift of the posterior lens capsule after cataract surgery is probably the cause, although indirectly, of the increased risk of retinal detachment after cataract removal. It would be desirable to prevent such a forward (anterior) shift.
One aspect of the invention resides in an intraocular lens implant with a lens optic and lens haptics configured to maintain a preoperative position of the posterior lens capsule during and after cataract removal and insertion of a lens implant. The lens haptics have proximal and distal portions, with the proximal portions being closer to the lens optic than are the distal portions. The lens optic extends in a lens optic plane and the distal portions of the lens haptics are in a common plane. The two planes are separated from each other by separation distance. That separation distance is preferably at least substantially the same dimension as or larger than a shift distance that the posterior lens capsule would otherwise traverse between its normal anatomical position and its shifted position if not constrained. The shifted position arises naturally after both removal of lens material within a lens capsule and removal of a portion of an anterior capsule.
For a better understanding of the present invention, reference is made to the following description and accompanying drawings, while the scope of the invention is set forth in the appended claims.
Turning to
Under conventional surgical techniques and implantation methods, the natural forward (anterior) shift distance that the posterior lens capsule traverses after cataract surgery when left unconstrained is 2-5 millimeters and is often 3-4 millimeters. The direction of the forward shift is anteriorly toward the cornea in the direction indicated by the direction arrow 9 as shown in
The embodiment of
The embodiment of
Preferably, the structure 50 is held in position by haptics 54, exemplified by right angled portions 56, 58, although such a haptics 54 may instead be inclined or curvilinear. For convenience, the structure 50 may be joined to the lens haptics 14E, although it may be arranged independent and separate from the lens haptics 14E. The haptics 54 may be made of the same material as the lens haptics 14E.
The structure 50 preferably has a larger diameter than the diameter of the lens optic implant 5 and lies in the same equator as the lens optic implant 5. That is, the structure 50 resides between the same two parallel planes 60, 62 that are separated from each other by a depthwise dimension of the lens optic implant 5 (see
Alternatively, the structure 50 may have the same or a smaller diameter than the diameter of the lens optic implant 5 in which case it would be arranged to be against the lens optic implant 5 to provide additional resistance against forces imposed by the posterior lens capsule that are responsible for the forward shift to otherwise occur.
Each of the embodiments of
The lens haptics (14A, 14B, 14C, 14D or 14E as applicable) are fixed to the lens optic 12 preferably with their proximal portion 16 along or within the confines of the lens optic 12 yet outside the field of vision of the lens optic 12 and with their distal portion 18 projecting beyond the confines of the lens optic 12. The lens haptics (14A, 14B, 14C, 14D or 14E as applicable) may be bonded or physically fit to the lens optic 12. The proximal portions 16 are closer to the lens optic plane 10 than are the distal portions 18. The lens haptics (14A, 14B, 14C, 14D or 14E as applicable) may be made of a polymer or metallic substance to be substantially rigid and may be made of the same material as the lens optic 12.
Preferably, the distal portions 18 are in a common plane 20 that is separated from the plane 10 of the lens optic by a separation distance SD. That separation distance SD is at least substantially the same as, although preferably greater than, the shift distance that the posterior lens capsule 5 would traverse normally (if left unconstrained after cataract removal) to its greatest extent as indicated by the direction arrow 9 in
The shift distance is an extent of a shift anteriorly that arises after conventional cataract surgery if no steps are taken to constrain the posterior lens capsule, because a portion of the anterior capsule (e.g., a central portion) and the cataract lens material are removed during the course of cataract surgery. The distal portions 18 may be free ends at which the lens haptics terminate. Alternatively, the distal portions 18 may be bends that allow the lens haptics to double back so that the free ends that are beyond the bends are closer to the lens optic plane than are the bends (distal portions).
The lens optic implant 5 with haptics 14A-14E of the invention may be implanted in the same manner as is known conventionally for conventional lens optic implants with haptics, i.e., through an incision and handled by forceps or like instruments. The lens optic implant 5 with haptics 14A-14D of
The present inventor recognized the need to prevent any amount of shift forward of the posterior lens capsule. The present invention permits the position of the posterior lens capsule, where it is prior to cataract surgery, to remain in the same position or largely so after cataract removal. The present invention may be in the form of an implant as previously described and/or as a device whose purpose is to keep the posterior lens capsule constrained against undergoing a forward (anterior) shift after cataract removal. Such an implant and/or device should be sterile prior to insertion into the eye.
The lens haptics 14A-14E should be relatively rigid, i.e., they should be rigid enough to resist deformation caused by capsular contraction as such deformation could conceivably cause them to lose their structure and fail to maintain the pre-operative position of the posterior lens capsule. Capsular contraction normally occurs along the axis of the lens haptics, and such contraction would have either no effect or an effect to further displace the optic in a posterior direction (toward the retinal surface). Such displacement would be resisted by the ocular components that are posterior to the posterior capsule (these non-compressible components consist of the vitreous body and wall of the eye, particularly the sclera). The contraction could, however, cause the haptics to impinge centrally on the visual axis and this would be undesirable.
The diameter of the capsular sac is remarkably similar from patient to patient. Therefore, if a line were drawn from the distal tip of one haptic to the distal tip of the other, it would probably be desirable for this dimension to be approximately 12-14 mm. It is unknown as to whether or not the function of the lens would be significantly altered by such a variation in dimension, but the present inventor suspects that it would not. The more important dimension is the distance between the plane of a line drawn between the distal tips of the two haptics (this line would be in a plane that was parallel to the lens optic), and the plane of the lens optic itself.
It is unknown as to whether or not one size lens haptics will fit all patients. As stated above, it is likely that a 12-14 mm distance between the tips of the two haptics would be the desirable size. As a corollary to this, endocapsular tension rings are horseshoe shaped plastic rings that are used to prevent capsular contraction after cataract surgery in eyes that are susceptible to this phenomenon. They are available in diameters between 12-14 mm, and the present inventor has used hundreds of these over the years. To date, the present inventor is unable to discern a clinical difference between the function of an endocapsular ring regardless of whether its diameter is 12, 13 or 14 mm. This does not mean that such a difference can not be discerned with a lens of the present invention, but it does indicate that contraction and distortion of the lens capsule generally compensates for the variations in size of various intraocular lenses and endocapsular tension rings.
While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be understood that various changes and modifications may be made without departing from the scope of the present invention.