Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Eye prosthesis – Intraocular lens
Reexamination Certificate
1998-11-02
2001-01-30
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Eye prosthesis
Intraocular lens
C623S006490
Reexamination Certificate
active
06179870
ABSTRACT:
The present invention has for its object a flexible intraocular implant formed in one piece and, particularly but not exclusively, an implant of this type intended to be placed in position in the capsular sac after ablation of the lens.
Intraocular implants may be divided into two large categories depending on the material with which they are made. So-called flexible intraocular implants and so-called rigid intraocular implants are distinguished. The former are made with materials of the silicone gel or pHEMA type, the latter generally being made from PMMA.
Rigid implants made of PMMA have been developed and manufactured for numerous years and their shape is perfectly defined. In particular, it is the case for the shape of the haptic loops, the function of these loops being to come to rest on the periphery of the capsular sac or on the internal wall of the eye in order elastically to maintain the optical portion of the implant opposite the pupil of the patient who has been implanted.
The tendency in eye surgery and, more precisely, in the positioning of intraocular implants in the eye, is to reduce very substantially the dimension of the incision which must be made in the cornea to position the intraocular implant. It must be added that, the implant is most often placed in position in the capsular sac after ablation of the lens, the techniques of ablation of the lens, particularly phako-emulsification, may be carried out by making only an incision of reduced dimensions, typically of the order of 3 to 4 mm. It was therefore interesting to have available intraocular implants capable of being placed in position in the eye through such an incision. However, it will be understood that the dimensions of the optical portion of the implant, i.e. its diameter, must be sufficient for this optical portion to perform its role of correction, even when the pupil is dilated to a maximum and despite a slight off-centering of the optical portion. It is therefore necessary that the optical portion presents a sufficient diameter, typically of the order of 5 to 6 mm.
Taking all these constraints into account, it will therefore be understood that only the use of a flexible material allowing the optical portion to be bent makes it possible to satisfy the double condition of passing through an incision in the cornea of reduced dimensions and of guaranteeing a sufficient diameter of the optical portion to allow optical correction, whatever the situation.
Consequently, a large number of so-called flexible intraocular implants have been developed to satisfy these two conditions. However, although the so-called flexible materials contribute an interesting solution to the problem of producing the optical portion, it is not so concerning the production of the haptic portion. In fact, the great flexibility of these materials means that the direct transposition of the haptics of the implants made of hard material cannot give satisfaction in the case of the flexible materials.
Taking this situation into account, two great types of solution have been proposed: on the one hand, it has been proposed to make implants in which the optical portion is flexible and the haptic portion is rigid, typically made of PMMA. These techniques are described in particular in Patent Application PCT/FR95/01344. This solution makes it possible, on the one hand, to benefit from pliable, flexible optics and, on the other hand, to use haptic loops made of PMMA of which the geometrical definition is perfectly mastered. It has also been proposed to make the haptic portion for the flexible implants, not via two loops in C or J form disposed diametrally with respect to the optics, but by providing two much more solid haptic portions terminating in arc-of-circle edges of sufficient length to ensure a sufficient contact between the periphery of the capsular sac and the haptic portion. Such flexible implants are described in particular in European Patent Application No. 93401744.3.
Nonetheless, it has already been proposed to make flexible implants in one piece, with a haptic portion constituted by two short loops of relatively conventional type. However, these implants are unsatisfactory insofar as, due to the very great flexibility of this material which presents a modulus of elasticity typically less than 0.2 MPa, the haptic loop, under the effect of the stresses resulting from its being positioned in the capsular sac, bends locally in the region of the connection of the loop to the periphery of the optical portion. This results in that the effective zone of contact between the haptic loops and the periphery of the capsular sac is reduced, which does not ensure perfect maintenance in place of the optical portion and which risks, especially, causing a deformation of the capsular sac with the damaging consequences that this brings about, or even a perforation of this capsular sac under the effect of the concentration of the pressure stresses.
This is shown in
FIG. 6
, the optical portion being referenced
2
, the haptic loops
4
and the periphery of the capsular sac
6
.
One object of the present invention is to provide a flexible one-piece intraocular implant presenting a haptic portion constituted by loops but which comprises a haptic portion having improved properties of maintenance and flexibility to obtain results substantially equivalent to those which are obtained with haptic loops made of PMMA.
To attain this object, the intraocular implant which comprises a substantially circular optical portion and two curved haptic loops each with a first connecting end at the periphery of the optical portion and a free end intended to come to rest on the internal wall of the eye, is characterized in that the optical portion and the haptic loops are made of the same flexible material of which the modulus of elasticity is included between 0.25 MPa and 1 MPa, and in that the width in the optical plane of each loop decreases from its connecting end to its free end such that the varation of the ratio between the variation of the bending moment applied to the loop and the inertia moment variation is substantially constant between two separate points of the loop over the whole length of the loop.
Thanks to this specific definition of the geometry of the loop, a distributed bending of the loop is obtained which thus enables it to adapt itself by bending to the different internal diameters of the capsular sac, avoiding a localized bending of the loop at the level of its connection to the optical portion and thus producing a considerable length of contact between the loop and the internal wall of the capsular sac or of the eye depending on the modes of implantation.
According to a preferred embodiment, each haptic loop further comprises a complementary arm separate from the loop proper and of which a first end is connected to the periphery of the optical portion near the connecting end of the loop and of which the other end is connected to the loop near its free end, the section of said additional arm being smaller than that of the loop, said arm being disposed on the concave side of the loop.
Thanks to the presence of a complementary arm associated with each haptic loop proper, not only the bending properties of the loops according to the definition given hereinabove are conserved, but, in addition, the inertia moment of each haptic loop is increased with respect to the risks of torsion of the loop with respect to its neutral axis. This thus makes it possible to avoid a relative movement of rotation of the optical portion with respect to the two loops, this movement of rotation risking producing a displacement of the optical portion such that the plane of the optical portion is no longer perpendicular to the optical axis of the eye.
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patent: 4990159 (1991-02-01), Kraff
patent: 5133749 (1992-07-01), Nordan
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paten
Ortuno Angel
Sourdille Philippe
Corneal Laboratoires
Willse David H.
Wolf Greenfield & Sacks P.C.
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