GB2293106A

GB2293106A - Intraocular lens

Info

Publication number: GB2293106A
Application number: GB9418497A
Authority: GB
Inventors: John L Pearce
Original assignee: Rayner Intraocular Lenses Ltd
Current assignee: Rayner Intraocular Lenses Ltd
Priority date: 1994-09-14
Filing date: 1994-09-14
Publication date: 1996-03-20
Anticipated expiration: 2014-09-14
Also published as: GB9418497D0; GB2293106B

Abstract

An intraocular lens of the type having a lens body and haptic loops extending from the periphery of the lens body at diametrally opposite locations, each said haptic loop having a free end and extending in a curve which is concave towards said lens body and is of increased curvature towards said free end such that there is a common tangent to said curve in the region of said free end, and to the lens body. <IMAGE>

Description

DESCRIPTION OF INVENTION Title: "Intraocular Lens" THIS INVENTION relates to intraocular lenses, that is to say to lenses adapted to be inserted surgically into the human eye to replace natural eye lenses which have been surgically removed, for example, because of cataract. Such intraocular lenses are known per se. The invention relates more particularly to intraocular lenses of the type which comprises a lens body of a generally circular or oval peripheral shape with two resilient haptic loops extending from the lens body at diametrally opposite positions on the lens periphery, each haptic loop extending in a curve substantially in a plane perpendicular to the lens axis, such curve being concave towards the lens body, the haptic loops terminating in respective free ends.Intraocular lenses of the last-noted type are herein referred to as being "of the kind specified".

An intraocular lens of the kind specified is adapted to be located in the capsular sac, posterior chamber of the eye, behind the iris, substantially in the region previously occupied by the removed natural lens.

When an intraocular lens of the kind specified has been correctly fitted in the posterior chamber of the eye, the haptic loops bear against the edge of the capsular sac at diametrally opposite locations and locate the lens body in the desired central position. An intraocular lens of the kind specified thus has a self-centering action during fitting and once fitted.

In the preferred method of extracting cataractous eye lenses and installing intraocular lenses, the cataractous lens is extracted through an incision or tunnel made anterior to the plane of the iris to afford access to the posterior chamber via the pupil opening and the intraocular lens is subsequently inserted through the same incision, into the capsular sac. Access to the interior of the capsular sac for both the removal of the natural lens and insertion of the intraocular lens is achieved by making a generally circular tear or opening, approximately 5mm to 8mm diameter, in central region of the anterior side of the capsular sac. This opening of the capsular sac is subsequently referred to as the "capsulorhexis".

It has been found that with conventional intraocular lenses of the kind specified, it happens, in some cases, that during insertion of the lens into the eye, the free end of the leading haptic loop can become snagged in the tissue of one or other of the structures of the eye or can pass through the pupil opening into the posterior chamber but fail to enter the capsulorhexis, in consequence of which correct location and centering of the lens body in the eye is impossible. It can also happen that the free ends of the haptic loops, located in the correct region, namely in the capsular sac, may nevertheless snag in the adjacent tissue preventing adjustment of the peripheral position of the haptic loop and thus interfering with the self-centering action of the lens.

It is an object of the present invention to provide an improved intraocular lens of the kind specified by which the above noted disadvantages are avoided or minimised.

According to the present invention there is provided an intraocular lens of the type having a lens body and haptic loops extending from the periphery of the lens body at diametrally opposite locations, each said haptic loop having a free end and extending in a curve which is concave towards said lens body and is of increased curvature towards said free end such that there is a common tangent to said curve in the region of said free end, and to the lens body.

An embodiment of the invention is described below by way of example with reference to the accompanying drawings, in which: FIGURE 1 is a front elevation view of an intraocular lens embodying the invention, i.e. a view along the optical axis of the lens, FIGURE 2 is a view in diametral section of a body of rotation about the lens axis, of which the lens of Figure 1 forms part, FIGURES 3 TO 6 illustrate the fitting, into the eye, of a conventional intraocular lens of the kind specified, illustrating faults which may occur and FIGURES 7 to 12 are similar figures illustrating the fitting of a lens embodying the invention.

Referring to Figures 1 and 2, the lens illustrated is made of transparent plastics, such as polymethylmethacrylate and comprises an approximately circular lens body 50 with two resilient haptic loops 52 extending from the periphery of the lens body 50 at diametrally opposite locations, the haptic loops 52 being formed integrally with the lens body 50.

The lens shown has the form which it would have if cut from a blank in the form of a body of rotation, about the axis 54 in Figure 2, of the section shown in Figure 2.

Such a blank would thus have a central region, affording the lens body 50, in the form of a bi-convex lens, an outer rim 56 in the form of a generally planar annulus lying in a plane perpendicular to the axis 54 but off-set to one side of the centre of the bi-convex central region and an approximately frusto-conical intermediate annular region 58 extending between the bi-convex region and the rim 56. The axis 54, of course, is coincident with the optical axis of the lens. The side to which the plane of rim 56 is offset is the side of the lens which is closer to the iris when the lens is fitted. In the finished lens, illustrated in Figure 1, the rim 56 and region 58 have been completely removed, apart from the haptic loop 52 and root portions or gussets 60 at the junctions of the haptic loops with the lens body 50.The rim 56 is of substantially uniform thickness and the region 58 is of substantially the same thickness as the rim 56. The portions of the periphery of the lens body 50 between the circumferential positions of the root portions 60 comprise circular arcs, of the same radius, about the lens axis. As shown in Figure 1 and as known per se, each haptic loop extends along a respective curve which meets a notional circle providing the aforementioned circular arcs tangentially and which, over most of its length, is concave towards the lens axis, the haptic loops 52 extending in opposite directions from the lens body. The haptic loops and associated root portions 50 are of identical shapes and exhibit rotational symmetry with respect to each other about the lens axis. The features described thus far are known per se in intraocular lenses.The lens may actually be formed by cutting unwanted material away from a blank of the form described, or may be moulded in the shape shown, or may be finished from a moulded blank approximating in shape to the finished lens.

Figures 3 to 6 show a known intraocular lens. It will be noted that, in this lens, the curve followed by each haptic loop in the unstressed condition extends, in the region adjacent the free end of the haptic loop and extending up to said free end, substantially along a circle concentric with the lens body about the lens axis. This construction results in a tendency for the free ends of the haptic loops to snag in tissue during insertion in the eye, as described in more detail below. Conventionally, the free ends of the haptic loops are enlarged and rounded, as illustrated, but even this does not altogether remove the problem.

By contrast, in the intraocular lens embodying the invention illustrated in Figures 1 and 2, the curve followed by each haptic loop 52 increases in curvature towards the free end of the haptic loop so that, as illustrated in Figure 1, there is a common tangent T1 to the lens body and the haptic loop, said tangent T1 touching the haptic loop adjacent the free end thereof. Indeed, as illustrated in Figure 1, the curve followed by each haptic loop preferably extends, adjacent the free end of the loop, in a relatively tight curve of such extent that a radius T2 from the centre of the lens body 50 is tangential to the haptic loop at a position adjacent, but still spaced from, the free end of the haptic loop. As a result of this configuration, the tendency of the free ends of the haptic loop embodying the invention to snag in surrounding tissue during and after insertion is virtually eliminated.

Figures 3 to 6 illustrate problems which may arise in fitting a conventional lens of the kind shown therein into the eye after removal of a natural eye lens with cataract whilst Figures 7 to 12 illustrate the relative ease with which corresponding steps may be conducted using an intraocular lens of the type described with reference to Figures 1 and 2.

Figures 3, 4 and 5 illustrate the insertion of a conventional intraocular lens into an eye from which the natural lens has been removed, by insertion of the intraocular lens through the incision or insertion tunnel 30 through which the natural eye lens has been removed. As shown, during this procedure, the intraocular lens is so oriented that the longest dimension of the lens extends along the insertion tunnel, i.e. the lens is inserted so that one haptic loop leads in the direction of insertion (indicated by arrow 12) and the other trails. Figures 3, 4 and 5 illustrate successive stages during such insertion.

As illustrated in Figure 4, the possibility exists for the free end of the trailing haptic loop to become snagged in the side of the insertion tunnel as illustrated at 13.

Furthermore, and more seriously, the free end of the leading haptic loop, indicated at 14 in Figure 4, can become caught on the anterior side of the capsular sac.

Whilst this occurrence would, of course, be observed by the surgeon who would attempt to correct the fault by rotation of the intraocular lens, about its axis, in the sense indicated by arrow 16, the required correction may be obstructed by the sides of the insertion tunnel. In the case a further push in the direction of insertion, indicated at 12, will not locate the leading haptic loop under the anterior capsule but will leave it on the anterior side.

By contrast, in installing an intraocular lens in accordance with the invention, as described with reference to Figures 1 and 2, the contour of the curled or returned end of the leading loop dilates the capsulorhexis (indicated at 3 in Figure 8) and allows the placing of the loop tip under the anterior capsule by pushing the lens downwards and in the direction 12. A rotation in direction 9 or direction 10, as illustrated in Figure 9, or a sideways adjustment is generally not required, but if required is facilitated by the form of the haptic loop ends.

The proximal or trailing loop tip (indicated at 6 in Figure 9) is then pushed through the capsulorhexis at point 5 (Figure 9) to complete the insertion.

Referring to Figure 10, the normal final positioning manoeuvre is a clockwise rotation in direction 10. Figures 6 and 12 illustrate respectively the conventional intraocular lens, and the lens of Figure 1 in a situation in which the capsule is torn, as indicated at 17. The contour of the haptic loops of the lens embodying the invention allows a rotation of the lens in direction 9.

A rotation in direction 10 would be inappropriate in the situation illustrated because the haptic loop shown nearest the tear would push through the tear, decentering the lens.

A haptic loop of conventional tip shape will snag and prevent rotation in direction 9 as illustrated in Figure 6.

It will be appreciated that many variations are possible within the scope of the appended claims. For example, whilst, in the embodiment described, the haptic loops 52 are integral with the lens body 50, the haptic loops may, as known per se, be separately formed plastics filaments, inserted at their one ends in respective bores extending chordally into the lens body and cemented therein.

Claims

1. An intraocular lens of the type having a lens body and haptic loops extending from the periphery of the lens body at diametrally opposite locations, each said haptic loop having a free end and extending in a curve which is concave towards said lens body and is of increased curvature towards said free end such that there is a common tangent to said curve in the region of said free end, and to the lens body.

2. An intraocular lens substantially as hereinbefore described with reference to and as shown in Figures 1, 2 and 7 to 12 of the accompanying drawings.

3. Any novel feature or combination of features described herein.