FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a lens and, more particularly, to various embodiments of a contact lens which can be used to correct vision problems such as presbyopia.

Typical vision problems such as myopia (nearsightedness), hyperopia (farsightedness) or presbyopia (loss of accommodation and subsequent loss of near and intermediate vision) are readily correctable using eyeglasses. However, some individuals prefer contact lenses for vision correction due to an active life style or aesthetic preferences.

Contact lens wearers who become presbyopic with age require additional corrective lenses to allow both near, intermediate and distance vision. While glasses provide a good optical solution for presbyopic contact lens wearers, eyeglasses can be less desirable to contact lens wearers for convenience and aesthetic reasons.

In attempts to provide a solution to this problem, contact lens makers have developed multifocal lenses which simultaneously focus light from a range of distances via several focal regions and bifocal lenses that include two simultaneously distinct lens powers, a central region for correction of myopia and a surrounding region for correction of hyperopia. The latter lenses translate with respect to the optical axis of the eye to provide both near and far vision correction depending on the eye gaze angle.

While bifocal and multifocal lenses can correct presbyopia, translation of the bifocal lens with respect to the cornea - anywhere from 2-6 mm (significantly more than standard contact lenses that typically translate about 0 to 0.5 mm) - can cause irritation and significant discomfort to the user while simultaneous focusing of light from several distances - as is the case for multifocal lenses - requires the user to 'process' light coming in from several distances. Furthermore, anatomical variability with respect to the distance between the optical axis and lower lid margin necessitates individual fitting of lenses and patient adjustment to correctly align the near- vision correction region of the bifocal lens to the optical axis during near vision tasks.

The above problems of bifocal and multi-focal lenses can be theoretically traversed by using a two lens system in which a first lens is positioned on the surface of the cornea and a second, translatable lens is positioned over the first lens. However, providing a lens system in which an outer lens translates over an inner lens while the inner lens remains stable on the cornea while also maintaining the entire lens system stable in the eye can be a challenging task.

Thus, it would be highly advantageous to have a lens system capable of correcting presbyopia while being devoid of the above limitations.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a contact lens comprising a continuous wall surrounding an internal volume, the contact lens being capable of rolling on a surface of a cornea such that opposing regions of the continuous wall move in opposite directions with respect to each other along an axis parallel to the surface of the cornea.

According to further features in preferred embodiments of the invention described below, opposing regions of the continuous wall include optical regions of different optical power.

According to still further features in the described preferred embodiments the volume is filled with a fluid.

According to still further features in the described preferred embodiments a first regions of the opposing regions has a first optical power and a second region of the opposing regions has a second optical power.

According to still further features in the described preferred embodiments the contact lens is shaped as an oblate spheroid preferably with a concave cornea-contacting surface.

According to still further features in the described preferred embodiments the continuous wall is fabricated from a hydrogel, silicone, silicone hydrogel (SH) or fluorosilicone-acrylate.

According to still further features in the described preferred embodiments the oblate spheroid is 5-20 mm in diameter.

According to still further features in the described preferred embodiments the oblate spheroid is has a base curve radius of 7.8- 10.0 mm.

According to still further features in the described preferred embodiments an internal surface of the continuous wall is fabricated from, or coated with, hydrophobic material and the volume is filled with a hydrophilic fluid. According to another aspect of the present invention there is provided a contact lens comprising a first material less pliable than a second material, wherein an end portion of the contact lens is formed from the first material.

According to still further features in the described preferred embodiments the end portion is circumferential and surrounds a central portion made from the second material.

According to still further features in the described preferred embodiments the first material and the second material are silicone and the first material exhibits a lower Shore A than the second material.

According to still further features in the described preferred embodiments the end portion of the contact lens has a non-zero optical power.

According to still further features in the described preferred embodiments the lens is shaped so as to translate over a carrier lens when in an eye.

According to still further features in the described preferred embodiments a base curvature of the end portion is different than that of the central region.

According to still further features in the described preferred embodiments a cornea- contacting surface of the lens is hydrophobic.

According to still further features in the described preferred embodiments the contact is fabricated from silicone hydrogel with a Modulus of 0.1 to 2.5 MPa or silicone with a Modulus of 0.27 to 8.68 MPa.

The present invention successfully addresses the shortcomings of the presently known configurations by providing a lens configured for correcting presbyopia while being stable and comfortable to wear and use.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings:

FIGs. 1A-B illustrates the shape of the present lens prior to (FIG. 1A) and following (FIG. IB) positioning over the surface of a cornea.

FIG. 2 illustrates the front and back surfaces of the lens.

FIG. 3 illustrates the forces acting on the front and back surfaces of the lens.

FIGs. 4A-B illustrate one embodiment of the present lens showing opposing surfaces of the lens. Opposing walls of the lens are indicated by different shading for illustrative purposes. FIGs. 4A-B illustrate 'rolling' of lens walls and movement of opposing wall regions.

FIGs. 5A-B illustrate the lens of FIG. 4 when positioned over the eye during gaze forward (FIG. 5a) and gaze down (FIG. 5b). Opposing walls of the lens are indicated by different shading for illustrative purposes.

FIGs. 6A-6B illustrates a lens suitable for use in a two lens system for correcting vision disorders.

FIGs. 7A-B illustrate the lens of FIGs. 6A-6B mounted over a carrier lens under gaze forward (FIG. 7A) and gaze down (FIG. 7B) conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of a lens system that can be used to correct visions in hyperopic, myopic or ametropic individuals with presbyopia. Specifically, the present invention can be used to provide both near, intermediate and far vision while traversing comfort and usability problems of prior art bifocal and multifocal lenses.

The principles and operation of the present invention may be better understood with reference to the drawings and accompanying descriptions.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details set forth in the following description. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

Individuals who are contact lens wearers and become presbyopia during their mid-forties find out that their contact lenses do not provide adequate solution for both near and distance vision tasks. Multifocal contact lenses as well as translating lenses (both rigid and soft) are available commercially but have not gained significant market share. Multifocal contact lens reduce vision quality while bifocal lenses require significant fitting effort and cause significant discomfort in many individuals.

Approaches for traversing limitations of presently used bifocal lenses have been described in the prior art. For example, US20080097600, the entire contents of which is incorporated herein by reference, describes a movable ophthalmic lens system which includes a carrier positionable on a portion of an eye, and a movable ophthalmic lens arranged for movement over a surface of the carrier. The assembly is configured such that the movable ophthalmic lens is responsive to ocular muscular movement so as to move in translatory motion over the surface of the carrier. Although this solution can in theory address comfort problems and provide near and far vision, it does not take into account the forces present in the eye environment (eyelid normal and lateral forces, as well as adhesion forces between the carrier and cornea and lens and carrier).

Another problem of current alternating contact lens for presbyopia is correct fitting for the distance between Lower Lid Margin to the Center Of Pupil (LLM-COP). If the LLM-COP is larger than the ridge to the bifocal transition line, the lens won't translate enough to provide near vision. However, if the LLM-COP distance is too small, the patient may experience double vision (both focal distances are within the pupil area). Current bifocal contact lens solution requires production of a few predetermined sizes and matching to ensure correct fit, however, these lenses can still fail to provide adequate vision correction in clinical practice.

While reducing the present invention to practice, the present inventors have devised a single body (one continuous wall/surface) lens which can be used for correction of presbyopia. The present inventors have also devised a contact lens which can be used as a piggyback lens in a two lens system for correcting presbyopia.

Thus, according to one aspect of the present invention, there is provided a contact lens for correction of vision disorders including presbyopia. As used herein, the term "lens" refers to a light-passing element. The lens can be any shape and configuration and can have regions of zero, negative or positive optical power as well as cylindrical power.

The lens is fabricated from a continuous wall surrounding an internal volume. The contact lens is configured to be capable of rolling on a surface of a cornea such that opposing regions of the continuous wall move in opposite directions with respect to each other along an axis parallel to the surface of the cornea. By providing the wall of the lens with regions of various optical power, one enables a lens which is capable of optical correction of far and near vision when such regions of the continuous wall are aligned or misaligned.

The lens can be a collapsed sphere, e.g., an oblate spheroid-like shape with the proximal (cornea-contacting) wall being concave to match the curvature of the cornea.

In order to design a lens capable of such functionality, the present inventors examined the forces on such a lens when positioned in an eye.

In order to assess the motion of a contact lens in the eye environment, one must consider the forces and pressures acting on, and resulting from, the contact lens - eye environment interaction. Pressure and force values were derived from Roba et al. (Friction on contact lenses Tribol Lett 2011), Ming et al. (Centering mech. of soft lenses, 1999) and Young et al. (influence of soft contact lens design, 1993).

A collapsed sphere-type lens fabricated from a thin, soft material, (e.g. Silicon, Silicon Hydrogel (SH) and/or Hydrogel with total thickness ranging between 50 to 800 microns stretched over a cornea forms the dome shown in FIGs. 1A - IB. The dome-shaped lens includes two domed surfaces/walls lying one on top of the other, a "front" or distal surface and a "back" or proximal surface (FIG. 2). The total area of the lens which is in contact with the cornea is equal to the area of the front surface in contact with the back surface (a collapsed sphere-like lens is totally symmetric and rolls on the corneal surface as such, at any given position, the internal surface of the lens will be identical to the surface between the lens and the cornea).

Under such conditions, the frictional forces acting on the two contact areas (back surface to cornea and front surface to back surface) are a function of their respective frictional coefficients [(Kj _μ) alone. In addition, the force required to shift the "front" surface over the "back" surface (to roll the front surface over the back surface) would be equal to the force required to flex and bend the material and the force of friction between surfaces (external and internal).

FIG. 3 summarizes the forces acting on the lens. F ₂ is controllable and is a function of thickness, material, geometry and distance between walls, the latter denoted ΔΧ, as: F ₂ =f (thickness, material, geometry, ΔΧ). Fi is the force of the lid on the front surface. In order to ensure that the front surface moves over the back surface with no appreciable sliding of the back surface over the cornea, i.e. that the lens rolls over the cornea rather than slide over it, the lens has to be designed to provide Ρ _μ2 >Ρι>Ρ _μ ι+Ρ ₂ .

In order to meet the above force equation and provide the requisite rolling movement, the present lens is designed with the following properties:

(i) Material - silicon Hydrogel (SH) with modulus value from 0.1 to 2.5 MPa; Silicon between 0.27 MPa (Shore/durometer 10) to 8.68 MPa (shore/ durometer 80).

(ii) Geometry and dimensions - diameter between 6-20mm, wall thickness can vary between 20-700 mm. Areas of optical power can be thinner or thicker according to corrective power desired.

(iii) Spacing between walls and volume - walls can be 0-1 mm apart and the volume can be 0—500 mm . The volume can be filled with a non-optical fluid such as air, saline, water and the like or it can be filled with an optical fluid to provide near or far sight vision correction. In the latter case, the lens can be provided with an optical region for additional vision correction (e.g. for correcting for near vision while the entire lens around the particular optical region provides far vision correction).

One embodiment of the present lens which is referred to herein as lens 10 is shown in FIG.s 4A, 4B, 5A and 5B.

As is shown in FIGs. 4A-B, lens 10 is formed from a contiguous wall 12 surrounding a volume 14.

In the embodiment shown in FIGss 4A-B, lens 10 is shaped as an oblate sphere with a concave back surface. Lens 10 can be fabricated from silicone, silicon hydrogel, Hydrogel, RGP and the like, with a surface roughness of 20-1500Microns. When not positioned in the eye, lens 10 can be 6-20 mm in diameter and up to 1 mm in thickness. Once positioned in the eye, lens 10 can adapt to the shape of the cornea to completely or partially flatten. Lens 10 can include one or more optical regions 16 of various focusing power. Such optical regions 16 can have zero, positive or negative power depending on the use of lens 10.

Optical regions 16 can have an area of 3 mm 2 to 60 mm 2 and a shape and thickness suitable for the optical power desired.

FIGs. 5A-B illustrate lens 10 positioned over a corneal surface during gaze forward (FIG. 5A) and gaze down (FIG. 5B) showing movement of optical regions 16 and 16'.

A presbyopic configuration of lens 10 can include two optical regions a first optical region 16 having a positive diopter (e.g. +1 to +2.5) and a second optical region 16' having a negative diopter (e.g. -2 to -4). At gaze forward, optical region 16' is aligned with the optical axis of the eye thus providing far vision correction. At Gaze down, rolling of the lens on the corneal surface moves optical region 16' out of the optical axis and brings optical region 16 with near vision correction into the optical axis of the eye.

Lens 10 can include regions of higher thickness (e.g. at 16 and/or 16') that can act as 'roll stop' regions. Such regions would increase the resistance of lens 10 to roll once positioned at the 'edge' (periphery) of lens 10.

Lens 10 can be fabricated using well known approaches such as injection/blow molding, vacuum forming, machining and the like.

Coating of materials on the inner and outer surfaces of the lens can be effected using plasma deposition and the like.

The present inventors have also devised a lens suitable for use in a two lens system for correcting vision disorders and in particular presbyopia.

Thus according to another aspect of the present invention, there is provided a contact lens which includes an end portion formed from a first material which is less pliable than a second material forming a non-end portion of the lens.

Several configurations of such a lens are envisaged herein. FIGs. 6A, 6B, 7A and 7B illustrate one embodiment of such a lens which is referred to herein as lens 50. Lens 50 includes a central portion 54 formed from the second material surrounded by a ring-like end portion 56 formed from the first material (FIG. 6A). As is further described hereinunder, such a configuration of lens 50 is particularly advantageous when lens 50 is used as a carried lens in a piggyback lens system for correcting presbyopia. FIG. 6 illustrates lens 50 when out of the eye (carrier lens 52 shown in FIG. 6B), FIGs. 7A-B illustrate lens 50 mounted over carrier lens 52 during gaze forward (FIG. 7A) and gaze down (FIG. 7B).

Lens 50 is sized and configured to efficiently translate over carrier lens 52 (preferably a hydrophilic lens fabricated from Silicon hydrogel/Hydrogel or the like) without appreciable movement of carrier lens 52 over cornea or displacement/detachment of lens 50 from carrier lens 52. Such efficient translation is a function of both lens configuration (less pliable lens 50 edge or periphery) and the front surface of lens 52 and back surface of lens 50, and in particular, the back surface of central portion 54.

Lens 50 is 6-15 mm in diameter with a radius of curvature of 7-9 mm. Several approaches can be used to make end portion 56 of lens 50 less pliable than central portion 54. Such approaches do not employ variable thickness but rather use of different materials and durometer. For example, lens 50 can be fabricated from silicon Hydrogel (SH) with Modulus values ranging from 0.1 to 1.9 MPa (with central portion 54 having a lower MPa value than end portion 56, e.g. 0.5 MPa for central portion 54 and 1.5 MPa for end portion 56) or from Silicone having a Shore A value of 20 to 80 (between 2.0 MPa to 9.7 MPa) with central portion 54 having a lower Shore A value than end portion 56 [e.g. Shore A value of 20 for central portion 54 and Shore A value of 50 for end portion 56].

The relatively higher pliability of portion 54 can also be provided via one or more holes or a pattern of openings. For example, portion 54 can include a single central hole that covers at some or all of the area of portion 54.

The pliability of central portion 54 is selected such that it adapts (conforms with) the front curvature of carrier lens 52. Since the friction between hydrophilic and hydrophobic surfaces is lower than the friction between carrier lens 52 and the cornea, lens 50 will translate on carrier lens 52 which will remain relatively stationary on the cornea.

Lens 50 can include a lid engagement element 58 for engaging a lower lid 60. When a user gazes down lid engagement element 58 engages lid rim 62 and prevents lens 50 from moving down with carrier lens 52 thereby causing lens 50 to translate over carrier lens 52 as is shown in FIGs. 7A-B. Lid engagement element 58 can be a protrusion on the external surface of lens 50. Such a protrusion can be wedged shaped with a height (maximum) of 0.1-1 mm. Lens 50 is designed to fit any type of carrier lens 52 including, for example, an off the shelf SH/Hydrogel spherical non-spherical or cylindrical lens. Lens 50 does not interfere with the optical correction of carrier lens 52 when mounted thereupon, e.g. when lens 50 is mounted on lens 52, the optical power region of lens 50 does not reside within the optical power region of lens 52 during gaze forward (e.g. central region 54 of lens 50 does not have any optical power).

The base curve and geometry of lens 50 are selected so as to form and maintain adhesion between lenses 50 and 52 during gaze forward and gaze down and translation between these two states. For example, a lens 50 with a base curve (BC) of 8.0 will 'float' (and thus will be less stable) over a carrier lens 52 having a front surface with a BC of 7.5 mm; a lens 50 with a BC of 7.0 mm will be more stable over such a carrier lens 52 with increased resistance to translation.

In addition, the more pliable central portion 54 will adapt its central radius to that of the front curve of carrier lens 52 and thus form strong adhesion therewith. The less pliable edge portion 56 will include region(s) of optical power and variable thickness and a base curve that can be different than that of central portion 54. Due to its lower pliability (higher rigidity) and a base curve that does not match that of carrier lens 52, edge portion 56 will not conform well to the front curvature of lens 52. As a result, adhesion forces between lens 52 and 50 will be lower and the gap therebetween will enable fluid to flow between lens 50 and lens 52. The lower adhesion force and presence of a lubricating fluid between lenses 50 and 52 (at edge portion of lens 50) will facilitate translation of lens 50 over lens 52 since lid forces on lens 50 will overcome adhesion forces between lenses 50 and 52 (without causing lens 52 to translate over cornea).

As used herein the term "about" refers to 10 % margins.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.