HK1074819A - Method for cast molding contact lenses with a rounded edge form - Google Patents

Description

Method for cast molding contact lenses having rounded edge shapes

Background

The present invention relates generally to the manufacture of contact lenses and, more particularly, to a method for cast molding contact lenses having a rounded edge that does not require specialized post-processing steps.

Historically, contact lenses have been manufactured by machining a lens material that is button (or block) shaped on either its front or back surface to produce an unfinished lens product having a desired fit, or "base curve", and vision correction to compensate for one or more refractive errors of the eye. These refractive disorders include myopia, hyperopia, astigmatism, presbyopia, and the like. With conventional machining techniques, the optical surface of the unfinished lens needs to be polished in order to remove a ring, commonly referred to as a "rotating ring", from the unfinished lens, which ring is created by the machining process. The edges of the lens are also typically polished to produce a smooth edge geometry or profile to maximize wearer comfort and prevent eye injury. The edge polishing step is particularly important in the manufacture of "hard" lenses, where the lens material is relatively hard and inflexible and even small defects on the edge can produce irritation in the wearer's eye.

The above-described mechanical processes are labor intensive and have been widely replaced by cast molding of lenses. In conventional cast molding techniques, both the front and back mold halves are manufactured to the desired lens prescription. Each mold section is produced using injection molding techniques. A mold insert tool, for example made of metal, ceramic, etc., is set, mounted or fixed in an injection molding machine. A mould part or mould half is then produced, which has the contour of the insert. Thus, the mold sections may include a negative impression of the desired front or back lens surface, or a profile corresponding to the desired front or back lens surface.

The two mold halves are assembled together and a lens material, such as a curable polymerizable monomer mixture, is introduced between the assembled mold halves. After the cast molding step, subsequent processing steps are applied, which may include, for example, curing, demolding, hydration (in the case of hydrogel lenses). In addition, edge polishing operations are often performed to smooth the edge profile of the lens.

Methods of cast molding contact lenses, particularly toric contact lenses, have been described by applolonio et al in U.S. patent No.5,611,970, which is incorporated herein by reference in its entirety.

Several methods have been developed for cast molding contact lenses in bulk. Cast-in-one lenses are lenses in which all of the surfaces, front, back and edges of the lens are molded as part of one mold pair and no post-processing polishing or machining operations are performed to produce the final lens product.

Unfortunately, while integrally molded lenses provide an inexpensive and flexible alternative to machining and polishing cast molded lenses, integrally molded lenses are sometimes uncomfortable to the wearer and may even injure the eye, especially after prolonged use.

The shape and size of the contact lens rim has proven to have a significant impact on the comfort level and conjunctival health of the wearer. Typically, an integrally molded lens will have a lens edge shape that is "knife-edged," or "pointed" in some manner and does not represent a polished edge or an edge that has historically been manufactured for improved wearer comfort.

Conventional integrally molded lens wearers are known to suffer from eye irritation and a decrease in eye "end of day comfort". In addition, long-term wearers have observed that, with the use of fluorescent dyes, there is a "scratch" mark formed on the sclera, the scratch mark being caused by the interaction between the lens and the eye. In order to achieve a more desirable edge geometry and provide a more comfortable lens, some lens manufacturers will apply additional, separate post-processing steps such as edge polishing in molding the lens with another unitary body. Polishing cast lenses generally removes the knife-edge or sharp edge profile produced by conventional cast molding processes. Unfortunately, however, the additional manufacturing steps tend to increase the cost of the final lens product.

It would be highly advantageous to provide a process by which a lens can be cast while producing a lens having a desired, substantially smooth or rounded edge geometry without the need for a post-processing polishing step.

Summary of The Invention

Accordingly, a method is provided for cast molding contact lenses having rounded edge surfaces in one piece. Advantageously, by practicing the present invention, lenses can be produced having an edge shape that provides enhanced comfort and/or safety without the need for costly and time consuming post-forming processing steps.

In general, the method for producing contact lenses, in accordance with the present invention, includes providing a tool insert or tool, such as a backface tool, having a surface substantially corresponding to the desired contact lens surface and a convex curve along its outer or peripheral radius. The tool is used to form a mold section that substantially defines a negative cavity in one surface of the final lens product. For example, the tooling is positioned in a molding machine, such as a conventionally designed molding apparatus. A moldable composition, such as a polymeric material or a precursor composition of a polymeric material, is introduced into the molding apparatus and subjected to conditions effective to form a mold section having a negative impression of the surface of a tool. The mold section formed by the tool is a back mold section. In other words, the surface of the tool substantially corresponds to one surface, preferably the posterior surface, of the contact lens to be formed. Thus, the tool may be a back side tool that substantially defines the base curve of the contact lens product. As will be described in greater detail below, the convex curve of the tooling when used to form the back mold section provides a contact lens having a desired rounded edge shape while not requiring a post-forming processing step.

For example, to form a rounded edge contact lens, a back tool having a convex curve along its outer radius is positioned in a molding machine, such as a conventional injection molding machine. A first mold portion is formed having a negative impression of the tool surface. This first mould part is assembled with a second mould part. The second mold section can be formed in a conventional manner and preferably substantially defines a negative cavity in the front, or anterior, surface of the contact lens to be produced. The assembled first and second mold sections form a lens-shaped mold cavity, and the method includes forming a contact lens piece in the lens-shaped mold cavity of the assembled mold sections. Upon demolding or removal from the mold part, an integrally molded contact lens piece is obtained having a rounded edge shape or surface.

The contact lens piece after demolding can be a final contact lens. However, the contact lens piece after demolding can be hydrated or further hydrated to form a finished contact lens having a rounded edge surface. An important advantage of the present invention is that the contact lenses of the invention preferably do not require a post-forming (after molding) process to alter the circular configuration of the contact lens pieces or the peripheral edge surfaces of the contact lenses. Post-forming treatments of the contact lens or contact lens piece, such as demolding, hydration, sterilization, packaging, etc., do not require modification of the rounded edge surface configuration.

The portion of the back side tool that forms the periphery of the lens is convex in shape, preferably having a radius of at least about 0.05mm or greater. Accordingly, the first mold portion formed by the tool insert has a concave outer edge surface. It will be appreciated by those skilled in the art that both the tool insert and the mold section formed therefrom, in accordance with the present invention, are substantially different in shape from conventional back tool inserts and conventionally produced back mold sections.

Preferably, in accordance with the present invention, the angle of intersection formed between the assembled first and second mold sections is at least about 100, and more preferably in the range of about 100 to about 170, on the lens side of the lens shaped mold cavity.

The invention also includes a tool, preferably a back tool, suitable for cast molding a contact lens, such as a contact lens having a circular peripheral surface in a mold section being manufactured. According to this embodiment of the invention, the tool generally comprises an insert adapted to be placed in a casting machine when forming the first mould part, in particular when forming the back mould part, which has a negative impression of one surface of the tool. In order to form the rounded edge surface of the final lens product, the surface of the tool comprises a first surface portion which takes the basic shape of a lens surface, preferably the posterior lens surface, of a contact lens and a second surface portion which defines a convexly curved outer peripheral edge surface of the insert. The second surface portion may be defined by a continuous curve having a radius of curvature of about 0.05 mm. Alternatively, the second surface portion may be defined by a series of facets, or a combination of facets and curves approximating a convexly curved surface.

In another aspect of the invention, a mold is provided that is suitable for producing, e.g., cast molding, a contact lens, preferably a contact lens having a rounded edge surface. The mold generally comprises a first mold section having a surface which takes the basic shape of the negative of one lens surface, preferably the posterior lens surface, of a contact lens to be cast with the mold and a convex outer edge surface, and a second mold section having a surface which takes the basic shape of the negative of the lens surface, preferably the anterior lens surface, of the opposite lens surface to be cast with the mold. The first and second mold sections are adapted to be assembled together, such as by a conventional method, to define a mold cavity in which an integrally cast, rounded edge contact lens or contact lens piece according to the invention is formed.

In another aspect of the invention, a cast unitary contact lens having a circular peripheral edge surface is provided. Such contact lenses may be produced using some of the methods, tools, and molds described herein.

It is to be understood that each feature described herein, and each combination of two or more such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent.

Brief description of the drawings

The advantages of the present invention will be more readily understood by reference to the following description when considered in connection with the accompanying drawings wherein:

FIGS. 1A and 1B are cross-sectional views of a conventional molding process for forming conventional contact lenses;

FIGS. 2A-2D are cross-sectional views of some examples of integrally cast contact lenses made using conventional molding techniques;

FIG. 3 is a cross-sectional view of an integrally cast contact lens having a substantially smooth, rounded edge profile made by the method of the present invention;

FIGS. 4A and 4B are a cross-sectional view and a front view, respectively, of a conventional tool insert used in conventional contact lens manufacturing techniques to form a mold section for cast molding a contact lens;

fig. 5 is a cross-sectional view of an integrally cast contact lens made by another conventional molding technique.

Fig. 6 is a front view of a tool insert used in a method of the present invention to form a mold section for cast molding a contact lens having a substantially smooth, rounded edge.

FIG. 7 is a cross-sectional view of the insert of the present invention taken along line 7-7 of FIG. 6; and

fig. 8 is a cross-sectional view of a molding apparatus for forming a rounded edge contact lens according to one method of the present invention.

Specification

Several methods for cast molding contact lenses have been disclosed. The present invention provides the convenience of cast molding to produce a substantially smooth rounded edge shape or surface without the need for costly post-processing steps.

Conventional cast molding techniques for making cast-in-one lenses produce a lens with a sharp, sharp-edged profile. As noted above, sharp edges are sometimes smoothed or rounded by a polishing step that is separate from the cast molding process.

Turning now to FIG. 1A, FIG. 1A shows in cross-section two mold halves 20, 30, sometimes referred to hereinafter as "casting cups", as assembled together during conventional cast molding techniques. A lens material, such as a curable mixture of polymerizable monomers, is introduced into a lens shaped mold cavity 40 to form a unitary cast lens article, said mold cavity 40 being defined between casting cups 20, 30.

Any suitable lens material or lens material precursor may be used in forming the present contact lenses and lens bodies according to the present invention. The resulting contact lenses and lens bodies can be rigid, rigid yet gas permeable, flexible, and/or hydrophilic. Preferably, for example, the contact lens or lens body for use in hydration may be soft and in the form of a hydrogel and/or a highly oxygen permeable, that is, a high Dk, material. One particularly useful class of lens materials is hydrophilic silicone-containing materials. Such hydrophilic silicone-containing materials are high Dk materials. And may have many advantageous advantages of both silicone polymer materials, such as cross-linked silicone polymer materials, and hydrogel-forming polymer materials. Contact lenses made from hydrophilic silicone-containing materials often have relatively high moduli and are advantageous, for example, in providing a reduced risk of eye irritation when formed to include a circular peripheral edge shape or surface in accordance with the present invention.

In the example shown in fig. 1, one casting cup 20 substantially defines a negative cavity for the back or posterior surface (base curve) of the lens, and one casting cup 30 substantially defines a negative cavity for the front or anterior surface of the lens.

In commercially available lenses, the point at which the two mold halves meet is typically selected as the outer periphery of the finished lens. As shown in fig. 1A, the mold cups 20, 30 meet at a point 50. This point 50 substantially defines the molded lens edge. The edges of the integrally molded lens conventionally represent a parting line 60 between the male and female casting cups 20, 30.

Another example of such a conventional arrangement is shown in fig. 1B, which has a back mold portion 70 and a front mold portion 80 that form a mold cavity 90, and points 100 that define the periphery of the lens.

It can thus be seen that conventional molding techniques produce a lens having a lens edge shape that is "knife-edged," or "sharp. Typical lens profiles formed by conventional cast molding techniques are shown in fig. 2A, 2B, 2C and 2D.

Rather, as will now be explained, the method of the present invention produces a substantially smooth rounded edge profile. A contact lens 110 formed by the method according to the present invention is shown in fig. 3.

Importantly, the illustrated lens 110 is produced in an integrally molded state without a post-molding step intended to alter the peripheral edge shape or configuration. As shown, a lens 110 produced by a method according to the present invention has a rounded smooth edge 112.

Although the lens 110 may be seen to have certain processing steps that are conventionally associated with this type of lens, such as demolding, hydration, inspection, packaging and sterilization, the edge profile of the lens 110 is not substantially different from its original molded shape.

The lens 110 is shown produced by modifying the insertion of a tool conventionally used to form the casting cups (i.e., mold halves) used to cast the lens.

As is well known in the art, between contact lens cast molding, each mold section (e.g., back mold 20 and front mold 30 in fig. 1) is formed by injection molding a resin in the mold cavity of an injection molding machine. Mounted on the injection molding machine is a "tool (hereinafter sometimes referred to as a" tool insert ") for forming an optical surface cavity in a mold section. Although each mold section is typically used only once for casting a single lens, injection molding tools are used to make hundreds of mold sections (i.e., mold halves).

The tools used to make the mold sections are manufactured to extremely high specifications. Roughness or other surface defects on the tool are not allowed, since these defects are transferred to all the mold parts made therefrom. Any such defects on the surface of the mold sections are transferred to the molded contact lens. The tool is typically made of brass, stainless steel, nickel or some combination thereof.

Turning now to fig. 4A and 4B, fig. 4A and 4B illustrate a tool 120 manufactured in a conventional manner.

Generally, to make a back mold (such as mold half 20 shown in fig. 1A), tool 120 includes at least one base curve (represented by curve 122) to provide fit and/or refractive correction. The correction is, for example, spherical, annular, multifocal, bifocal, etc. In addition, the tool 120 includes a form 124, the form 124 forming a portion of the lens edge geometry, the form 124 sometimes being tapered. The tapered edge on the back tool is generally flat or concave to obtain a taper on the molded lens edge.

In other conventional tools (not shown), the edge forms 124 are omitted from the tool and the base curve is extended toward the lens periphery. For example, the back-side tool may not have a defined edge feature but rather the substrate curve itself. In this case, edge tapering of the molded lens is typically accomplished by the surface profile of the front mold tool, which includes a tapered edge feature.

Fig. 5 shows a cross-sectional view of a lens 150 produced in this manner, i.e., where the base curve (partially represented by dashed line 152) extends to the lens periphery 154 and no edge features are provided on the back side tooling (not shown). As can be seen, this technique also produces a lens edge geometry that is sharp, as shown in fig. 2A-2D.

Those skilled in the art will appreciate that at sufficiently high magnification, the sharp bevel of the lens shown in fig. 2A-2D and 5 may be suitably slightly curved or rounded, since shrinkage, for example, in the mold and thus the molded lens may not closely replicate the geometry of the tool insert. However, the integrally molded lens profile shown is sharp and sloped and, in addition, does not represent a more desirable rounded profile that is only conventionally available in machined or cast lenses that have been post-processed for polishing to alter, for example, the rounded peripheral edge of the lens.

As further described herein, a method for cast molding a contact lens according to the present invention comprises the steps of: providing a backface tool, said backface tool having a surface corresponding to a desired contact lens surface and at least one convex curve along an outer radius thereof; positioning the tool in a molding apparatus, such as a conventional injection molding machine; introducing a moldable material into the molding apparatus and subjecting the material to conditions selected from, for example, conventionally used conditions effective to form a first mold portion having a negative cavity in the tool surface; assembling the first and second mold sections together to form a lens-shaped mold cavity therebetween; and forming a contact lens piece having a rounded edge shape in the lens-shaped mold cavity of the assembled mold section. Upon demolding, the contact lens piece itself is a contact lens product, or may be subjected to hydration in order to provide a contact lens product.

More specifically, referring now to fig. 6-8, in contrast to conventional cast lenses, the present invention intentionally places at least one convex radius or curve at the outer or peripheral edge of the back tool insert. Such convex radii may be produced on the tool insert by a series of flats, such as very short flats, that are close together to simulate a continuously curved convex shape, or by a combination of flats and convex curves.

Referring now specifically to fig. 6 and 7, in one embodiment of the present invention, a tool insert 160 is provided. The tool insert 160 has a convex shape substantially as described above. For a lens 110 made in accordance with the present invention and shown in fig. 3, the tool 160 used in making the lens 110 includes a convex curve along its outer radius, or peripheral edge surface 162.

Unlike prior tool inserts used in the manufacture of conventional cast lenses, the present invention provides a method for manufacturing contact lenses having a cast convex curve radius at the lens edge periphery.

Referring now also to fig. 8, fig. 8 illustrates a portion of an assembled pair of casting cups 164 for cast molding a rounded edge contact lens in accordance with the present invention. Cup pair 164 includes a first back mold half 166 that fits together with a second front mold half 168. The convex outer radius of the tool 160 used to make the back mold segment 166 may be about a 0.05mm radius or greater.

When mold halves 166, 168 are assembled together, the final cast unitary lens, such as lens 110, has a substantially smooth rounded edge as shown. A convex curve on a portion of the back tool 160 forming the lens periphery can be used to produce a lens having a more circular shape, as seen in lens 110 of fig. 3.

Preferably, the angle of intersection of the mold tools 166, 168 on the lens side (designated by the symbol α in fig. 8) is greater than about 100 ° when the two mold halves 166, 168 are assembled together. In the case of the lens 110 shown in fig. 3, on the lens side, the angle of intersection of the two mold halves, in the dry state, is 140 ° on the untreated or unhydrated lens member, while producing a finished or hydrated contact lens 110 having a much more rounded or less sharply defined edge surface. It should be understood that the angle of intersection of the two mold halves on the lens side can be made less than or greater than about 140, for example, angles greater than 100 can be used, for example, in the range of about 100-170 or more.

After the mold halves 166, 168 are assembled, the round-edged contact lens can be cast using conventional procedures as known to those skilled in the art and described above. Although it is clear that some processing steps performed after cast molding, such as in the case of hydrogel hydrophilic lenses, hydration, may vary somewhat from the finished lenses made according to the present invention, the peripheral edge shape of the finished lenses remains substantially unchanged and is much smoother than the conventional "knife-edge" edges described above.

By practicing the present invention, one-piece cast lenses having desired (rounded) edges can be produced without the need for specialized post-form polishing and machining steps to form the desired peripheral edge shape.

While a particular method of manufacturing a rounded edge contact lens having a rounded peripheral edge surface or shape has been described above in accordance with the present invention for purposes of illustrating the manner in which the invention may be advantageously utilized, it is to be understood that the invention is not limited thereto. Accordingly, any and all modifications, variations, or equivalent arrangements which may occur to those skilled in the art, should be considered to be within the scope of the present invention as defined in the appended claims.

Claims

(modification according to article 19 of the treaty)

1. Delete

2. Delete

3. Delete

4. Delete

5. Delete

6. Delete

7. Delete

8. Delete

9. Delete

10. Delete

11. Delete

12. Delete

13. Delete

14. A tool useful in the manufacture of a mold section for casting contact lenses, said tool comprising:

an insert adapted to be placed in a molding apparatus when forming a first mold section having a negative cavity in the surface of a tool, the surface of the tool comprising a first surface portion that takes the basic shape of the posterior surface of a contact lens and a second surface portion that defines the convexly curved outer peripheral edge surface of the insert.

15. The tool of claim 14, wherein the convexly curved outer peripheral edge surface of the insert has a radius of at least about 0.05 mm.

16. The tool of claim 14, wherein the convexly curved outer peripheral edge surface of the insert is formed by a series of flats approximating a convex curve.

17. The method of claim 14, wherein the convexly curved outer peripheral edge surface of the insert is formed by a combination of a plurality of flat surfaces and a plurality of convex curves.

18. Delete

19. Delete

20. Delete

21. A method for producing a contact lens product, said method comprising:

providing a backface kit comprising a first surface portion and a convexly curved second surface portion, said first surface portion substantially corresponding to a desired contact lens posterior surface, and said second surface portion surrounding said first surface portion;

positioning a back-side tool in a molding apparatus;

introducing a polymeric moldable material into a molding apparatus and subjecting the moldable material to conditions effective to form a first polymeric mold section having negative cavities of first and second surface portions of a back tool;

assembling the first polymeric mold section and the second mold section together to form a lens-shaped mold cavity therebetween; and

a contact lens element is formed in the lens shaped mold cavity of the assembled mold sections.

22. The method of claim 21, wherein the contact lens member is formed with a rounded edge.

23. The method of claim 21, wherein the forming step comprises polymerizing a hydrogel-forming component in the lens-shaped mold cavity.

24. The method of claim 23, further comprising demolding the contact lens piece and hydrating the contact lens piece to form a hydrogel contact lens having rounded edges.

25. The method of claim 21, wherein the lens-shaped mold cavity defines an intersection angle on the lens side between the assembled mold sections, said intersection angle being at least about 100 °.

26. The method of claim 21, wherein the lens shaped mold cavity defines an intersection angle on the lens side between the assembled mold sections, said intersection angle being in the range of about 100 ° to about 170 °.

27. The method of claim 21, wherein the assembling step comprises assembling the first polymeric mold section and the second polymeric mold section together to form a lens-shaped mold cavity therebetween.

28. The method of claim 21, wherein the convex curve along the outer radius of the surface has a radius of at least about 0.05 mm.

29. A mold useful in the production of contact lenses comprising:

a first polymeric mold section having a concave outer edge surface and a surface that takes the basic shape of the negative of the posterior surface of the contact lens; and

a second polymeric mold portion, said second polymeric mold portion having a surface which takes the basic shape of the negative of the anterior surface of the contact lens;

the first and second polymeric mold sections are adapted to fit together to define a lens-shaped mold cavity having a contact lens shape with a circular outer peripheral edge surface.

30. The mold of claim 29, wherein the lens-shaped mold cavity defines an intersection angle on the lens side between the assembled mold sections, the intersection angle being at least about 100 °.

31. The mold of claim 29, wherein the lens shaped mold cavity defines an intersection angle on the lens side between the assembled mold sections, the intersection angle being in the range of about 100 ° to about 170 °.

32. A mold according to claim 29, wherein the concave outer edge surface of the first mold portion has a radius of at least about 0.05 mm.

33. A contact lens sized and adapted for placement over a cornea of an eye, said contact lens comprising:

a lens body comprising a hydrogel material and having an anterior surface, a posterior surface, and a circular outer peripheral edge surface extending from the anterior surface to the posterior surface,

the lens body is formed by a method that includes cast molding with a first polymer mold portion having a surface that takes a negative base shape of the back surface and a concave outer peripheral surface and a second polymer mold portion having a surface that takes a negative base shape of the front surface, and the lens body is not subjected to a post-forming treatment to alter the rounded configuration of the outer peripheral edge surface.

34. The contact lens of claim 34, wherein the lens body comprises a hydrophilic silicone-containing material.

35. A contact lens sized and adapted for placement on a cornea of an eye, the contact lens comprising:

a lens body comprising a hydrophilic silicone-containing material, said lens body having an anterior surface, a posterior surface having a rounded outer peripheral edge surface extending from the anterior surface to the posterior surface, said lens body formed by a method comprising cast molding with a first polymer mold portion having a surface taking the negative basic shape of the posterior surface and a concave outer peripheral surface and a second polymer mold portion having a surface taking the negative basic shape of the anterior surface, said contact lens providing enhanced lens wearer comfort compared to an identical contact lens without the rounded outer peripheral edge surface.

36. The contact lens of claim 35, providing enhanced scleral safety compared to an identical contact lens without the rounded outer peripheral edge portion.

37. The contact lens of claim 35, wherein the contact lens provides enhanced lens wearer comfort as compared to an identical contact lens having a sharp outer peripheral edge surface.

38. The contact lens of claim 36, wherein the contact lens provides enhanced scleral safety compared to an identical contact lens having a sharp outer peripheral edge surface.

39. The contact lens of claim 35, wherein the lens body is not subjected to a post-forming treatment to alter the rounded configuration of the peripheral edge surface.

40. The contact lens of claim 35, providing a refractive correction selected from the group consisting of spherical correction, annular correction (toroid correction), and multifocal correction.

41. A contact lens sized and adapted for placement over a cornea of an eye, said contact lens comprising:

a lens body comprising a hydrophilic silicone-containing material, said lens body having an anterior surface, a posterior surface, said posterior surface having a rounded outer peripheral edge surface extending from the anterior surface to the posterior surface, said lens body formed by a method comprising cast molding with a first polymeric mold section having a surface taking the negative basic shape of the posterior surface and a concave outer peripheral surface and a second polymeric mold section having a surface taking the negative basic shape of the anterior surface, said contact lens providing enhanced scleral safety compared to an identical contact lens without the rounded outer peripheral edge surface.

42. The contact lens of claim 41, wherein said contact lens provides enhanced scleral safety as compared to an identical contact lens having a sharp outer peripheral edge surface.

43. The contact lens of claim 41, wherein the lens body is not subjected to a post-forming treatment to alter the rounded configuration of the peripheral edge surface.

44. The contact lens of claim 41 providing a refractive correction selected from the group consisting of spherical correction, annular correction, and multifocal correction.

45. A contact lens sized and adapted for placement over a cornea of an eye, said contact lens comprising:

a lens body comprising a material having a modulus about equal to or greater than a modulus of a hydrophilic silicone-containing material, the lens body having an anterior surface, a posterior surface having a rounded outer peripheral edge surface, the outer peripheral edge surface extending from the front surface to the rear surface, the lens body being formed by a method, the above process is cast molded using a first polymeric mold portion and a second polymeric mold portion, said first polymeric mold portion having a surface taking the negative basic shape of the back surface and a concave outer peripheral surface, and said second polymeric mold portion having a surface which takes a negative basic shape of the front surface, the contact lenses described above provide enhanced lens user comfort as compared to the same contact lenses without the rounded peripheral edge surface.

46. The contact lens of claim 45, providing enhanced scleral safety compared to an identical contact lens without the rounded outer peripheral edge surface.

47. The contact lens of claim 45, wherein said contact lens provides enhanced lens wearer comfort as compared to an identical contact lens having a sharp outer peripheral edge surface.

48. The contact lens of claim 46, wherein said contact lens provides enhanced scleral safety as compared to an identical contact lens having a sharp outer peripheral edge surface.

49. The contact lens of claim 45, wherein the lens body has not been subjected to a post-forming treatment to alter the rounded configuration of the peripheral edge surface.

50. The contact lens of claim 45 wherein the lens body comprises a material selected from the group consisting of hydrogel-forming polymeric materials and mixtures thereof.

51. The contact lens of claim 45, providing a refractive correction selected from the group consisting of spherical correction, annular correction, and multifocal correction.

52. The contact lens of claim 45, wherein the lens body comprises a material having an oxygen permeability about equal to or greater than the oxygen permeability of a hydrophilic silicone-containing material.

Claims (20)

1. A method for producing a contact lens, said method comprising:

providing a backface tool, said backface tool having a surface and a convex curve, said surface substantially corresponding to a desired contact lens surface, and said convex curve along an outer radius thereof;

positioning a tool in a molding apparatus;

introducing a moldable material into a molding apparatus and subjecting said moldable material to conditions effective to form a first mold portion, said first mold portion having a negative cavity of a tool surface;

assembling the first and second mold sections together to form a lens-shaped mold cavity therebetween; and

a contact lens element is formed in the lens-shaped mold cavity of the assembled mold sections.

2. The method of claim 1 wherein the contact lens member is formed with a rounded edge.

3. The method of claim 1, further comprising demolding the contact lens piece and hydrating the contact lens piece to form a contact lens having rounded edges.

4. The method of claim 1, wherein the lens-shaped mold cavity defines an intersection angle on the lens side between the assembled mold sections, said intersection angle being at least about 100 °.

5. The method of claim 1, wherein the lens shaped mold cavity defines an intersection angle on the lens side between the assembled mold sections, said intersection angle being in the range of about 100 ° to about 170 °.

6. The method of claim 1, wherein the first mold section is a back mold section for forming a posterior surface of a contact lens.

7. The method of claim 1, wherein the convex curve radius along the outer radius of the surface is at least about 0.05 mm.

8. The method of claim 1, wherein the forming step comprises polymerizing the lens-forming ingredients in a lens-shaped mold cavity.

9. A mold suitable for use in the production of contact lenses comprising:

a first mold section having a surface shaped to contact the negative base of the posterior surface of the lens and a concave outer edge surface;

a second mold section having a surface that contacts the substantially negative shape of the anterior surface of the lens; and

the first and second mold portions are adapted to fit together to define a mold cavity.

10. The mold of claim 9 wherein the mold cavity is in the basic shape of a contact lens having a rounded edge.

11. The mold of claim 9, wherein the mold cavity defines an intersection angle on the lens side between the assembled mold sections, said intersection angle being at least about 100 °.

12. The mold of claim 9, wherein the mold cavity defines an intersection angle on the lens side between the assembled mold sections, said intersection angle being in the range of about 100 ° to about 170 °.

13. The mold of claim 9, wherein the first mold portion concave outer edge surface has a radius of at least about 0.05 mm.

14. A tool suitable for use in the manufacture of a mold section for casting contact lenses, said tool comprising:

an insert adapted to be placed in a molding apparatus when forming a first mold section having a negative cavity in the surface of a tool, the surface of the tool comprising a first surface portion and a second surface portion, the first surface portion contacting the basic shape of the posterior surface of the lens and the second surface portion defining the convexly curved outer peripheral edge surface of the insert.

15. The tool of claim 14, wherein the convexly curved outer peripheral edge surface of the insert has a radius of at least about 0.05 mm.

16. The tool of claim 14, wherein the convexly curved outer peripheral edge surface of the insert is formed by a series of flats approximating a convex curve.

17. The method of claim 14, wherein the convexly curved outer peripheral edge surface of the insert is formed by a combination of a plurality of flat surfaces and a plurality of convex curves.

18. A contact lens sized and adapted for placement on a cornea of an eye, said contact lens comprising:

a lens body having a front surface, a back surface and an outer peripheral edge surface extending from the front surface to the back surface and having a rounded configuration, the lens body formed by a method comprising cast molding with a first mold section having a surface with a negative base shape of the back surface and a concave outer edge surface and a second mold section having a surface with a negative base shape of the front surface, the lens body not being subjected to a post-forming treatment to alter the rounded configuration of the outer peripheral edge surface.

19. The contact lens of claim 18 wherein the lens body comprises a material selected from the group consisting of hydrogel-forming polymeric materials and mixtures thereof.

20. The contact lens of claim 18, wherein the lens body comprises a hydrophilic silicone-containing material.