Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2000-07-06
2002-08-13
Sugarman, Scott J. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C264S002500, C351S16000R
Reexamination Certificate
active
06431706
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to the manufacture of contact lenses and more specifically relates to methods for cast molding contact lens with a molded edge that requires no dedicated post-processing steps.
Contact lenses have historically been made by machining a lens material, in button (or block) form on front and back surfaces thereof to produce an unfinished lens product having the required fit, or “base curve”, and visual correction, to compensate for one or more refractive abnormalities of the eye. Such refractive abnormalities may include myopia (nearsightedness), hypermetropia (farsightedness), astigmatism, presbyopia and the like. Using conventional machining technology, the optic faces of the unfinished lens require polishing in order to remove rings, known as “turning rings”, on the unfinished lens that have been created by the machining process. Typically the edge of the lens is also polished to produce smooth edge geometry, or profile, in order to maximize wearer comfort and prevent injury to the eye. The edge polishing step is particularly important in the manufacture of “hard” lenses, in which the lens material is relatively rigid and inflexible and even small defects on the edge can cause irritation in the wearers' eye.
The machining process described above, being very labor intensive, has been widely replaced by cast molding of the lens. In conventional cast molding techniques, front and back surface mold halves are made for the required lens prescription. Each mold section is produced by injection molding techniques. A mold insert tool, for example made of metal, ceramic or the like, is provided and secured or fixed in an injection molding machine. A mold section, or mold half, is then produced having the contour of the insert. Thus, the mold section may include a negative impression of, or a contour which corresponds to, the desired lens front or back surface.
The two mold halves are assembled and lens material, for example a curable, mixture of polymerizable monomers, is introduced between the assembled mold halves. After the cast molding steps, subsequent processing steps are employed, 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.
A method of cast molding contact lenses, particularly toric contact lenses, is described in Appollonio, et al, U.S. Pat. No. 5,611,970 which is incorporated in its entirety herein by reference.
Methods for fully cast molding contact lenses have been developed. Fully cast molded lenses are lenses in which all surfaces, front, back and edge of the lens are molded as part of a mold pair and no post processing polishing or machining operations are performed to yield the final lens product.
Unfortunately, although fully molded lenses provide an inexpensive and flexible alternative to machined and polished cast molded lenses, fully molded lenses are sometimes uncomfortable for the wearer and may even harm the eye, particularly after long term use.
It has been shown that the form and size of the edge of a contact lens have significant effects on wearer comfort and conjunctival heath. It is conventional that a fully molded lens will have a lens edge form which is “chiseled”, or “pointed” in some way, and is not representative of a polished edge or an edge which had been historically manufactured to improve wearer comfort.
Wearers of conventional fully molded lenses have been known to suffer from eye irritation and reduction in “end of day comfort” of the eye. Moreover, long term wearers have been observed, with the use of a fluorescein dye, to have ‘scuff’ marks formed on the sclera, the scuff marks being caused by interaction between the lens and eye. 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 otherwise fully molded lenses. Polishing the cast molded lens will generally remove the chiseled or pointed edge profile that is conventionally produced by cast molding. Understandably, however, the additional manufacturing step will tend to increase the cost of the final lens product.
It would be highly advantageous to provide a method by which a lens could be cast molded, the resulting lens having a desirable, substantially smooth or rounded edge geometry, without the need for post processing polishing steps.
SUMMARY OF THE INVENTION
Accordingly, a method is provided for fully cast molding contact lenses having rounded edge surfaces. Advantageously, by implementation of the present invention, lenses can be created with an edge form providing enhanced comfort and/or safety without the need for costly and time consuming post formation processing steps.
Generally, methods for producing contact lenses, in accordance with the present invention comprise providing a tooling insert or tool, for example, a back surface tool, having a surface generally corresponding to a desired contact lens surface and a convex curve along an outer or peripheral radius thereof. The tool is used to form a mold section which generally defines a negative impression of a surface of the final lens product. For example, the tool is positioned in a molding apparatus, such as a molding apparatus of conventional design. 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 the tool. The mold section formed by the tool is a back surface mold section. In other words, the surface of the tool generally corresponds to a face, preferably the posterior face, of the contact lens to be formed. Thus, the tool may be a back surface tool generally defining the base curve of the contact lens product. As will be described in more detail hereinafter, the convex curve of the tool, when used to form a back surface mold section, provides a contact lens having the desired rounded edge form without the need for post formation processing steps.
For example, to form the rounded edge contact lens, the back surface tool having the convex curve along the outer radius thereof is positioned in a molding apparatus, for example, a conventional, injection molding apparatus. A first mold section having a negative impression of the surface of the tool is formed. This first mold section is assembled with a second mold section. The second mold section may be made in a conventional manner and preferably generally defines a negative impression of a front, or anterior, surface of the contact lens to be produced. The assembled first and second mold sections form a lens-shaped cavity, and the method includes forming a contact lens member in the lens shaped cavity of the assembled mold sections. Upon demolding or removal from the mold sections, a fully molded, contact lens member having a rounded edge form or surface is obtained.
The demolded contact lens member may be the final contact lens. However, the demolded contact lens member may be hydrated or further hydrated to form the final contact lens with a rounded edge surface. One important advantage of the present invention is that the present contact lenses preferably do not require post-formation (after being molded) processing to alter the rounded configuration of the outer peripheral edge surface of the contact lens member or contact lens. Post-formation processing such as demolding, hydration, sterilization, packaging and the like of the contact lens or contact lens member does not alter this rounded edge surface configuration.
The portion of the back surface tool that forms the lens periphery is convex in form, preferably having a radius of at least about 0.05 mm or larger. Correspondingly, the first mold section formed by the tooling insert has a concave outer edge surface. It will be appreciated by those skilled in the art that both th
Ocular Sciences, Inc.
Stout, Uxa Buyan & Mullins, LLP
Sugarman Scott J.
Uxa Frank J.
LandOfFree
Method for cast molding contact lenses with a rounded edge form does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for cast molding contact lenses with a rounded edge form, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for cast molding contact lenses with a rounded edge form will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2879143