Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Eye prosthesis – Intraocular lens
Reexamination Certificate
2001-10-16
2004-06-15
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Eye prosthesis
Intraocular lens
C623S006410, C623S006390, C623S006490
Reexamination Certificate
active
06749634
ABSTRACT:
The present invention relates to the field of intraocular implants, and more precisely to the field of lenses that are implanted after cataract surgery consisting in removing the natural lens from the capsular bag through a central and anterior capsulotomy (capsulorexis) having a diameter of 5 millimeters (mm) to 6 mm. As a result, the posterior and equatorial portions of the capsular bag are preserved.
BACKGROUND OF THE INVENTION
Replacing the natural lens with an implant has become an operation that is commonplace in the field of cataract surgery.
Until now, the implants used have not had the ability to restore any faculty of accommodation to an operated patient. It is known that the loss of accommodation which leads to presbyopia stems not from loss of function in the ciliary muscle and the associated zonular fibers, but firstly from a hardening of the lens material contained in the capsular bag, and secondly from an increase in the dimensions of the lens due to the patient aging. Hardening of the lens material opposes any modification being made to its shape by the capsular bag when the capsular bag is relaxed by the zonular fibers (near vision). The increase in the size of the lens has the consequence that only a fraction of the amplitude in the variation of the dimension of the ciliary muscle is transmitted to the capsular bag, since during muscle relaxation, a portion of this amplitude is used up in tensioning the zonular fibers before beginning to cause the outward displacement that generates a modification in the shape of the lens.
With a young subject, the lens material on its own, i.e. when not enclosed in the capsular bag, has approximately the shape taken up by the lens when in the de-accommodated state (far vision). This is the state in which the lens material tends to harden with age. Still with a young subject, the rest shape of the lens, i.e. of the lens material in the capsular bag and in the absence of any connection with the zonular fibers, is close to that of the accommodated state (near vision). In other words, the elasticity of the capsular bag constrains the lens material to leave its own rest state and take up an accommodated shape. Hardening opposes this molding of the lens material by the capsular bag.
Likewise, with a young subject and in the accommodated state of the eye, the axial zonular fibers are always tensioned without slack. This enables them to transmit the amplitude of ciliary muscle deformation to the capsular bag in full. The increase in the size of the lens causes the axial zonular fibers to be relaxed when the ciliary muscle is contracted, so relaxation of the muscle has an effect on the capsular bag only over a fraction of its stroke, with the first portion of this increase in diameter having the sole effect of retensioning the axial zonular fibers so as to cause them to take up a position in which they are able to drive the capsular bag over a second portion of the increase in diameter of the ciliary muscle.
Thus, when cataract surgery fully conserves both the posterior portion of the capsular bag and its equatorial portion, and leaves a peripheral fraction of its anterior wall in place as well, the conditions are such that accommodation is capable of being recovered. The full capacity of the capsular bag for elastic deformation is recovered; in the absence of any lens material, the bag shrinks elastically and the zonular fibers are again under tension. It is then possible to take advantage of the still-functioning “drive assembly” constituted by the ciliary muscle, the zonular fibers, and the remaining portions of the capsular bag.
Numerous implants have been designed that attempt to make use of contraction and relaxation of the ciliary muscle in order to modify the optical power of the eye. Implants are known comprising two pieces, a case received in the capsular bag and an optical portion inside the case. The case is supposed to track the shape of the capsular bag. As a result, at least in theory, the optical piece is caused to move along the optical axis of the eye, thus varying the optical power of the eye and thus providing vision accommodation. In this respect, mention can be made of document EP 0 337 390. It would appear that that implant provides poor performance since the mechanism for compressing the case produces only a very small amount of movement in the optical portion, so the faculty of accommodation is practically non-existent.
One-piece implants are also known comprising an optical central portion and a haptic portion (e.g. two radial arms extending from the periphery of the optical portion) having the function of being held captive in the collapsed equatorial zone of the capsular bag and by the formation of fibrosis. After the implant has been put into place between the collapsed membrane portions, the operating method then consists in maintaining the ciliary muscle in the relaxed state for the time required (a few weeks) to allow fibrosis to take hold of the ends of the haptic portions. During this time, the remainder of the anterior portion of the capsular bag shrinks, thus tending to stress the haptic portions towards the posterior portion of the bag and thus to press the optical portion against this posterior portion. At the end of fibrosis growth, the ciliary muscle is returned to normal control by the brain. Thus, when it contracts for near vision, the capsular bag is released, and the fibrosis zone tends firstly to tilt forwards with help from an increase in the internal pressure of the eye, and secondly to tighten radially, thereby causing the optical portion to move forwards, the radial shrinkage being transformed by the hinged or flexible haptic arms into a movement tending to cause the optical portion to protrude forwards. To accomplish this movement and the opposite movement when the ciliary muscle relaxes, the haptic portions are hinged to the edge of the optical portion or they are very flexible so as to be capable of moving or bending in front of and behind the mean plane thereof, in front for far vision and behind for near vision. In addition, the haptic portions slide in their sockets in the fibrosis tissue which has been generated between the collapsed portions of the capsular bag in the vicinity of its equator. That type of implant is described in document U.S. Pat. No. 5,674,282, for example.
In that device, the fibrosis tissue whose growth is encouraged is a factor which contributes to modifying interaction between the zonular fibers and the capsular bag and which makes it impossible to predict the final behavior of the implant during accommodation.
Finally, proposals have been made for another one-piece accommodating implant comprising an annular portion whose section is gutter-shaped and intended for being received in the equatorial zone of the capsular bag and from which there project arms connecting it to a central optical portion. Variation in the diameter of the equatorial zone of the bag towards and away from the center gives rise to radial thrust or traction on the arms, thereby causing the optical portion to move along the optical axis (see WO 99/03427).
In that device, the presence of the continuous outer annular portion constitutes a brake on deformation of the equatorial zone of the bag, and that diminishes the effectiveness of the implant in providing accommodation.
OBJECTS AND SUMMARY OF THE INVENTION
Unlike known devices, the present invention makes it possible to retain as much as possible of the accommodation faculties still available in an eye that has been subjected to a cataract operation.
A first object of the present invention is to provide a one-piece implant, and a second object is to provide an artificial lens device which comprises the implant and an intermediate piece between the implant and the capsular bag.
In the present description, the terms “anterior” and “posterior” should be understood in their meanings as used in ophthalmology, i.e. so far as the lens system is concerned, “anterior” is closer to the cornea, and “posterior” is further from the cornea. In the
Humanoptics AG
Willse David H.
Young & Thompson
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