WO1990009610A1

WO1990009610A1 - Flexible contact lens

Info

Publication number: WO1990009610A1
Application number: PCT/AU1990/000066
Authority: WO
Inventors: Brien Holden; Arthur Back
Original assignee: Unisearch Limited
Priority date: 1989-02-20
Filing date: 1990-02-20
Publication date: 1990-08-23

Abstract

Flexible contact lens having a posterior central portion and surrounding generally annular portions leading to the peripheral edge of the lens the radii of these portions, in cross section (1, 2 and 13) being selected to give an increase tear film thickness proximate region A being the junction of the central circular portion and the innermost annular portion and region B being proximate the junction of the outer and inner annular portions.

Description

FLEXIBLE CONTACT LENS Technical Field

The invention relates to contact lenses and in particular provides a flexible contact lens with improved movement from thicker tear film and preferably improved facilities to exchange tears, move and remove metabolic waste products from, and increase the oxygen available_, to, the cornea of the eye of the wearer of the lens. Background Art Flexible contact lenses have been generally accepted because of a number of well recognised advantages. However there is a problem in that each particular lens design must in some way address the problem of maintaining an adequate tear film between the lens and the wearer's eye.

Disclosure of the Invention

In broad terms one form of the invention can be described as a flexible contact lens having a posterior surface including a steepening of the inner periphery providing in use an increased tear film thickness beneath portions of the lens posterior surface.

Alternatively, the invention can be broadly described as providing a flexible contact lens having an overall convex anterior surface and an overall concave posterior surface, both anterior and posterior surfaces being . usually but not necessarily symmetrical about an axis of revolution.

In one embodiment the posterior surface of the lens comprises a central curved portion (which may be spherical or aspherical) cooperative with the anterior surface to produce desired optical characteristics, the central portion extending radially outwardly from said axis of revolution to a junction region of intersection between said central portion and an inner peripheral portion. The said junction region may be either centred or asymmetrical about said axis; an approximately annular (consisting of either a spherical or aspherical surface) inner peripheral portion, either centred or asymmetrical about said axis, adapted to assist in accumulating the tears when in use during surface contact with a user's eye, the intersection of said inner peripheral portion with a diametric plane containing said axis describes a curve of greater curvature (concave) than that of the curve generated by the intersection of an imaginary continuation of said central portion with said diametric plane at least for radially inner regions of the inner peripheral portion; and an approximately annular outer peripheral portion which may be either spherical or aspherical and convex or concave and either centred or asymmetrical about said axis providing a surface joining the inner portion to the edge of the contact lens, the outer peripheral portion being adapted to assist in accumulating tears and in providing a surface having an appropriate apposition to the conjunctiva to minimize pressure on conjunctiva yet allowing minimal interaction of the edge with the upper eyelid and palpebral conjunctiva, in the case when the diameter of the lens is similar to or larger than the corneal diameter. The curve described by the intersection of said outer peripheral portion with a diametric plane containing said axis being of lesser curvature than the intersection of an i aginery continuation of said inner peripheral portion with said diametric plane.

When the diameter of the contact lens is similar to or less than the corneal diameter the said outer peripheral portion is adapted to assist in accumulating tears, to provide a surface having an appropriate edge lift from the cornea, such that the moving contact lens has adequate clearance of its edge from the cornea and limbus such that a 'ski' effect exists, and to minimize the interaction between upper eyelid and palpebral conjunctiva and the lens edge, hence providing comfort to the eye of the wearer of the contact lens.

In one embodiment, the central portion of the back surface could be spherical and generated by a first arc revolved around said axis, said inner peripheral portion is spherical being generated by a second arc revolved about said axis and the radius of the second arc being less than the radius of the first arc, said oute,r , peripheral portion being generated by a third arc revolved about said axis and the radius of the third arc being greater than the radius of the second arc.

In a further embodiment, the central portion of the back surface could be aspherical and generated by a first curve revolved around or asymmetrical about said axis. In a still further embodiment, the inner peripheral portion is aspherical, either centred or asymmetrical about said axis, and joins the central portion (spherical or aspherical) at the junction region such that the inner peripheral portion leads away from the tangent to the central portion at the junction region more steeply..

In yet another embodiment, the surface of the i n-er peripheral portion can be generated by the revolution of a curve (spherical or aspherical) around the said axis -of revolution, the centre of curvature of said curve being offset from said axis, the intersection of the surface of the inner peripheral portion with a diametric plane containing said axis describes a curve which leads away from the tangent to the curve described by the intersection of said diametric plane and the surface of the central portion at the junction region more steeply

(towards the posterior) than does the curve of the central portion.

In a further embodiment, the outer peripheral portion is aspherical, either centred or asymmetrical about said axis, and smoothly joins the inner peripheral portion such that the outer peripheral portion leads away from the tangent to the surface of the inner peripheral portion at the junction region with a lesser curvature than does the inner peripheral portion (at least for more peripheral regions of the outer peripheral portion).

In still another embodiment, the outer peripheral portion can be produced by a toroidal surface generated by an arc of a convex curve revolved around a geometrical axis (spherical or aspherical), the said geometrical axis being translated from said axis of revolution and that the outer peripheral portion joins the inner peripheral portion at the junction region such that the outer peripheral convex portion leads away from the tangent to the surface of the inner peripheral portion at the junction region with a greater curvature than the inner peripheral portion and the surface being steeper (towards posterior), at least for more peripheral regions of the outer peripheral portion.

The central, inner peripheral and outer peripheral posterior portions can of course be formed by multiple

(not necessarily continuous) curves or a continuous curve and/or designed in such a fashion as to vary the pressure on the eye and to obtain the effect of tear film accumulation under a portion or portions of the contact lens.

In broad terms, the anterior surface may comprise one, two or more curves such that the central portion of the anterior surface co-operates with the central portion of the posterior surface to produce desired optical characteristics and that the peripheral portions join the central portion to the edge of the contact lens. The anterior peripheral portions are designed to provide a comfortable well shaped and smooth surface, over which the upper eyelid and palpebral conjunctiva can slide, as well as contribute to the movement capabilities of the contact lens such that appropriate interactions between the anterior peripheral portions and the upper eyelid and palpebral conjunctiva occur, the anterior peripheral portions do not make ineffective the posterior design features that allow accumulation of tears when in use after surface contact with the eye of the wearer of the contact lens. The anterior outer peripheral portion smoothly joins the inner peripheral portions to the edge of the contact lens and is of a shape that provides comfort to the eye of the wearer of the contact lens by appropriate taper and shape of the outer peripheral portion and the edge of the contact lens. One, two or more of the anterior peripheral curves may be spherical or aspherical, concave or convex in shape, continuous or discontinuous, centred or asymmetrical about said axis, it is understood that the invention relates to a contact lens with unique posterior surface design features and that many variations on the anterior surface are possible depending on the power (myopic, hyperopic, toric or multifocal correction) of the contact lens. It is intended that the anterior surface be designed so as to provide appropriate optical power, excellent comfort to the eye of the wearer, and must cooperate with the posterior design features to allow movement. It is understood that front surface shapes can enhance the movement of a contact lens, however, but without departing from the invention. The anterior surface can be formed by a single or multiple curves, either spherical or aspherical continuous or discontinuous, concentric or asymmetrical about said axis of contact lens and can be concave or convex in shape relative to the axis of said contact lens.

The present invention is useful for those traditional types of lenses having a binding problem in that they cease moving over the eye of the wearer or for those lenses which tend to drape the eye, although it can be useful in all flexible lenses. The lenses, by virtue of this design, produce thicker tear film portions underneath the contact lens than do conventional lenses. Brief Description of the Drawings

By way of example only, embodiments of the present invention will now be described with reference to the accompanying drawings, in which: -

Fig. 1A is a cross-sectional view of a first embodiment of a lens in accordance with the invention;

Fig. IB is a plan view of the lens of Fig. 1A;

Fig. 2A is a cross-sectional view of a second embodiment of a lens in accordance with the invention; and

Fig. 2B is a plan view of the lens of Fig. 2A; Fig. 3A is a cross-sectional view of another embodiment of a lens in accordance with the invention; and

Fig. 3B is a plan view of the lens of Fig. 3A. Best Mode for Carrying out the Invention

The lens of Figs. 1A, IB is of a diameter larger than corneal size and is typically produced from flexible materials such as hydrogels, εilicone elastomer and materials of similar properties.

The lens of Figs. 1A, IB includes a bicurve spherical anterior surface 8 and diameter CC. Clearly, where alternative optical, fitting or comfort characteristics are desired the anterior surface can be made aspherical or multicurved.

The posterior surface of the lens includes a Back Central Optic Zone (BCOZ) of diameter AA' . The Back Central Optic Zone (BCOZ) is defined by the revolution of the arc AOA' , of radius 1, about the axis of revolution 7. The radius 1 of the BCOZ is typically 6.0 to 12.0mm (more particularly 7.0 to 10.0mm), while the diameter CC is typically 12.0 to 16.0mm (more particularly 13.0 to 15.0mm). The anterior surface includes a central' portion DD', of radius 11 and its value depends on the optical power of the lens required. The outer portion, DC is derived using a simple curve of radius 12 to maximise comfort and fitting performance. The value of radius 12 is also

,*» dependent on the optical power of the contact lens required and the ability to provide a smooth, blended junction with both the central anterior surface and the posterior surface edge of the lens. On the posterior surface, surrounding the BCOZ in a generally annular manner is a first or inner peripheral curve AB. The inner peripheral curve is formed by the revolution of the arc AB about the axis 7. The arc AB in this case has a radius 2, although the centre of curvature of the inner peripheral curve 2 need not necessarily be on the axis 7. The radius of the inner peripheral curve 2 is typically 0.1 to 2.0mm steeper (more particularly 0.2 ^'to 0.8mm steeper) than the radius 1 of the BCOZ. The inner peripheral curve AB has a width (5) of 0.2 to 3.0mm, more usually 0.4 to 2 .0mm.

Surrounding the inner peripheral curve AB is an outer peripheral curve BC, again in generally annular form. The outer peripheral curve 3 in this case is generated by the revolution of the curve joining C and B about the axis 7, although the centre of curvature of the outer peripheral curve 3 need not necessarily be on the axis 7, and can also be aspherical. The radius of the outer peripheral concave curve 3 can be in the range 8.0 to 18.0mm, more particularly 9.5 to 15.0mm, while its cord width (6) is typically 0.2 to 3.0mm, more particularly 0.4 to 1.5mm. Where desired, for example due to manufacturing techniques available, the outer peripheral curve CB can be shaped as a revolution about an offset axis having its centre of curvature at F. The radius of this outer peripheral 'convex' curve 13 can be in the range 3.0 to 20.0mm, more particularly 6.0 to 15.0mm while its chord width (6) is typically 0.2 to 3.0mm, more particularly 0.4 to 2.0mm.

The peripheral edge C of the lens is shaped so as to present a smooth transition from the anterior surface to the posterior surface.

The lens of Figs. 2A and 2B is of a diameter smaller than corneal size and is typically produced from flexible materials such as silicone elastomer, copolymers, butyl acrylate or other material' of similar properties.

The lens of Figs. 2A, 2B includes a bicurve spherical anterior surface 8 and diameter CC. Clearly, where alternative optical, fitting or comfort characteristics are desired the anterior surface can be made aspherical or multicurved.

The posterior surface of the lens includes a Back Central Optic Zone of diameter AA' . The Back Central Optic Zone (BCOZ) is defined by the revolution of the arc AOA' , of radius 1, about the axis of symmetry 7. The radius 1 of the BCOZ is typically 6.0 to 11.0mm (more particularly 7.0. to 9.0mm), while the diameter of the contact lens CC is typically 8.0 to 13.0mm (more particularly 9.0 to 12.5mm).

The anterior surface includes a central portion, of radius 11 and its value depends on the optical power of the lens required. The outer portion, DC is derived using a simple curve of radius 12 to maximise comfort and fitting performance, and its value is also dependent on the optical power of the contact lens required. On the posterior surface, surrounding the BCOZ in a generally annular manner is a first or inner peripheral curve 2. The inner peripheral curve 2 is generated by the revolution of the arc AB about the axis 7. The arc AB In this case has a radius 2, although the centre of curvature of inner peripheral curve 2 need not necessarily be on the axis 7. The radius of the inner peripheral curve 2 is typically 0.1 to 2.0mm steeper (more particularly 0.2 to 0.8mm steeper) than the radius 1 of the BCOZ. The inner peripheral curve 2 has a width (5) of 0.2 to 3.0mm, more particularly 0.3 to 1.5mm.

Surrounding the inner peripheral curve 2 is an outer peripheral curve 3, again in generally annular form. The outer peripheral curve 3 is generated by the revolution of the curve joining C and B about the axis 7. The radius of the outer peripheral concave curve 3 can be in the range 8.0 to 15.0mm, more particularly 9.5 to 14.0mm, while its chord width (6) is typically 0.2 to 3.0mm, more particular 0.4 to 2.0mm.

Where desired, for example due to manufacturing techniques available, the outer peripheral curve CB can be shaped as a revolution about an offset axis having its centre of curvature F. The radius of this outer peripheral 'convex' curve 13 can be in the range 3.0 to 20.0mm, more particularly 5.0 to 15.0mm while its chord width (6) is typically 0.2 to 3.0mm, more particularly 0.4 to 2.0mm.

The peripheral edge C of the lens is rounded so as to present a smooth transition from the anterior surface to the posterior surface. The lens of Figs. 3A and 3B is of a diameter smaller than corneal size and is typically produced from flexible materials such as silicone elastomers, copolymers, butyl acrylate or other materials of similar properties.

The lens of Figs. 3A and 3B has a posterior surface the same as that described in Figs. 2A and 2B.

The lens of Figs. 3A and 3B includes a tricurve spherical anterior surface 8 of diameter CC-*-. Clearly, this same surface can be made aspherical or multicurved. The anterior central portion ΩO-- of radius 11 cooperates with the central posterior portion A * to provide appropriate optical correction; the anterior inner peripheral portion, DE, is derived using a simple curve of radius 12 joining smoothly to the central anterior portion and having a curvature greater than the central curve, the value of radius 12 depending on the central radius 11 and that the thickness of the contact lens normal to a tangent of the junction of the inner anterior and outer anterior peripheral portions is within the range of 0.10mm to 0.50mm, more particularly 0.20mm to 0.35mm; and an outer anterior peripheral curve EC smoothly joining the inner peripheral portion DE and having lesser curvature than the inner anterior peripheral curve. The outer anterior peripheral portion joins with the outer posterior portion at the lens edge, C, in such a fashion as to provide appropriate edge thickness in the range of 0.03mm to 0.20mm, more particularly 0.06mm to 0.15mm, roundness of the edge and smoothness of the surface so as to provide excellent comfort to the wearer of the contact lens. The lenses of Figs. 1, 2 and 3 whose surface when in contact with the eye of the wearer of the contact lens, with their unique posterior design features, will now maintain portions of increased tear film thickness corresponding to approximately an annular region near the junction of the central portion and the inner peripheral portion A and also to approximately annular sections corresponding to either sides of the junction region between the outer peripheral portion, and the inner peripheral portion B. Hence, portions of increased tear film thickness of a flexible lens can be obtained to provide lubrication so that enhanced movement of a contact lens can be obtained and maintained for previously said advantages of no lens binding and removal of metabolic waste products and debris, It will be recognised by persons skilled in the art that numerous variations and modifications may be made to the invention as described above without departing from the spirit or scope of the invention as broadly described.

Claims

CLAIMS : -

1. A flexible contact lens having a posterior surface including a steepening of the inner periphery providing in use an increased tear film thickness beneath portions of the lens posterior surface.

2. A flexible contact lens as defined in claim 1 having an overall convex anterior surface and an overall concave said posterior surface, both anterior and posterior surfaces being generally symmetrical about an axis of revolution.

3. A flexible contact lens as defined in claim 1 wherein the posterior surface of the lens comprises a central curved portion cooperative with the lens anterior surface to produce desired optical characteristics, the central portion extending radially outwardly from an axis of revolution to a junction region of intersection between said central portion and an approximately annular inner peripheral portion; the inner peripheral portion, adapted to assist in accumulating the tears when in use during surface contact with a user's eye, the intersection of said inner peripheral portion with a diametric plane containing said axis describes a curve of greater curvature (concave) than that of the curve generated by the intersection of an imaginary continuation of said central portion with said diametric plane at least for radially inner regions of the inner peripheral portion; and an approximately annular outer peripheral portion providing a surface joining the inner portion to the edge of the contact lens.

4. A flexible contact lens as defined in claim 3 wherein the curve described by the intersection of said outer peripheral portion with a diametric plane containing said axis being of lesser curvature than the intersection of an imaginery continuation of said inner peripheral portion with said diametric plane.

5. A flexible contact lens as defined in ciaim 2 further including a central portion of the back surface being spherical and generated by a first arc revolved around said axis, an inner peripheral portion being spherical and generated by a second arc revolved about said axis and the radius of the second arc being less than the radius of the first arc, an outer peripheral portion being generated by a third arc revolved about said axis and the radius of the third arc being greater than the radius of the second arc.

6. A flexible lens contact lens as defined in claim 3 wherein the central portion of the back surface being aspherical and generated by a first curve revolved around or asymmetrical about said axis.

7. A flexible contact lens as defined in claim 3 wherein the inner peripheral portion is aspherical and joins the central portion at the junction region such that the inner peripheral portion leads away from the tangent to the central portion at the junction region more steeply.

8. A flexible contact lens as defined in claim 3 wherein the surface of the inner peripheral portion being generated by the revolution of a curve (spherical or aspherical) around the said axis of revolution, the centre of curvature of said curve being offset from said axis, the intersection of the surface of the inner peripheral portion with a diametric plane containing said axis describes a curve which leads away from the tangent to the curve described by the intersection of said diametric plane and the surface of the central portion at the junction region more steeply (towards the posterior) than does the curve of the central portion.

9. A flexible contact lens as defined in claim 3 wherein the outer peripheral portion is aspherical and smoothly joins the inner peripheral portion such that the outer peripheral portion leads away from the tangent to the surface of the inner peripheral portion at the junction region with a lesser curvature than does the inner peripheral portion at least for more peripheral regions of the outer peripheral portion.

10. A flexible contact lens as defined in claim 3 wherein the outer peripheral portion being a toroidal surface generated by an arc of a convex curve revolved around a geometrical axis, the said geometrical axis being translated from said axis of revolution and that the outer peripheral portion joins the inner peripheral portion at the junction region such that the outer peripheral convex portion leads away from the tangent to the surface of the inner peripheral portion at the junction region with a greater curvature than the inner peripheral portion and the surface being steeper (towards posterior), at least for more peripheral regions of the outer peripheral portion.

11. A flexible contact lens as defined in claim 3 wherein the outer peripheral portion being adapted to assist in accumulating tears and in providing a surface having an appropriate apposition to the conjunctiva to minimize pressure on conjunctiva yet allowing minimal interaction of the edge with the upper eyelid and palpebral conjunctiva, in the case when the diameter of the lens is similar to or larger than the corneal diameter.