Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2002-03-20
2004-05-11
Sugarman, Scott J. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
Reexamination Certificate
active
06733124
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent application No. 2001-081556 filed on Mar. 21, 2001, and No. 2002-013081 filed on Jan. 22, 2002 including the specifications, drawings and abstracts is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to contact lenses adapted to be worn on a surface of an eyeball and including a generally circular central zone serving for providing an optical zone and an annular peripheral zone disposed around the central zone. More particularly, the present invention is concerned with such a contact lens that is novel in construction and that permits an enhanced lens wearing comfort as felt by a lens wearer.
2. Description of the Related Art
There is known a contact lens that is worn on a surface of a cornea of a human eye for treating myopia, hyperopia, astigmatism, presbyopia and the like. Since the contact lens is worn on the cornea accompanied with contact thereof with very sensitive surfaces of the cornea and eyelids of a lens wearer, it is material to ensure an excellent wearing comfort as felt by the lens wearer.
In general, the contact lens includes a generally circular central zone serving for providing an optical zone that transmits light to a pupil, and an annular peripheral zone integrally disposed radially outward of the central zone and serving for placing the contact lens on a predetermined position of the cornea. The peripheral zone is designed to permit a good circulation of tear fluid existing between the cornea and the contact lens. The contact lens has a back surface whose radius of curvature is substantially equal to that of the surface of the cornea of the lens wearer so that the back surface of the contact lens may suitably conform to the shape of the cornea of the lens wearer. Generally, this radius of curvature of the back surface of the contact lens is referred to as a base curve.
However, such a conventional contact lens as described above gives rise to a problem of discomfort as felt by the contact lens wearer when he or she wear the lens, although degrees of the discomfort may vary among individual wearers. In particular, a conventional contact lens of hard or rigid type gives the lens wearer a relatively large wearing discomfort. Thus, the conventional contact lens is insufficient to assure a good wearing comfort thereof.
In addition, the conventional hard contact lens is likely to suffer from a problem that dusts or other floating objects in the atmosphere are introduced into the tear fluid existing between the contact lens and the cornea. This results in significant deterioration of the lens wearing comfort as felt by the lens wearer, and sometimes gives rise to a burden on the lens wearer to remove the contact lens to wash it.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a contact lens which is novel in structure, and which is capable of eliminating or minimizing a discomfort as felt by a contact lens wearer when he or she wear the contact lens, and assuring an improved wearing condition of the lens, while preventing an entrance of the dust or the like into a tear fluid layer existing between the lens and the cornea.
The above and/or other objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to those modes of the invention and combinations of the technical features, but may otherwise be recognized based on the thought of the present invention that disclosed in the whose specification and drawings or that may be recognized by those skilled in the art in the light of the disclosure in the whole specification and drawings.
(1) A contact lens having a back surface adapted to face a cornea, wherein the back surface including (a) a generally circular central zone and (b) an peripheral zone disposed around the central zone, the central zone having a radius of curvature gradually decreasing from a center thereof toward a periphery thereof.
In the contact lens according to this mode of the invention, the radius of curvature of the back surface gradually decreases with an increase in a radial or lateral distance from the center of the central zone that serves for providing an optical zone. In this arrangement, the back surface of the central zone has a curve that is made gradually steeper from its center toward its periphery, so that a protrusion protruding backward of the contact lens, namely, protruding toward the side of the cornea is formed on the periphery of the central zone. The protrusion extends in a circumferential direction of the contact lens so as to surround the central zone. With the contact lens worn on a cornea of a lens wearer, this protrusion protrudes toward the cornea from the back surface of the contact lens, and is located closely adjacent to a surface of the cornea. In the presence of the protrusion, a tear fluid layer existing between the back surface of the contact lens and the cornea is narrowed or constricted at the peripheral portion of the central zone where the protrusion protrudes toward the cornea. Thus, the back surface of the contact lens is located closely adjacent to the surface of the cornea at this protrusion.
Accordingly, the contact lens of this mode of the invention permits an improved lens wearing comfort as felt by the lens wearer. In addition, since the protrusion partially narrows the tear fluid layer at the outer circumferential portion of the contact lens, unfavorable entrance of dusts or other floating objects in the atmosphere into the tear fluid layer is effectively limited or minimized, thus assuring an enhanced usability of the contact lens. It is presumed that these advantages of the present contact lens, namely, the improved lens wearing comfort and the limited entrance of the dusts into the tear fluid layer, stem from the following technical basis or reasons. Namely, the narrowed portion of the tear fluid layer located at the peripheral portion of the central zone may function as a barrier to the unfavorable entrance of the dusts into the tear fluid. In addition, the protrusion disposed at the periphery of the central zone and adapted to be located closely adjacent to the surface of the cornea may lead the contact to be desirably positioned relative to the cornea. That is, the presence of the protrusion may limit an amount of displacement of the contact lens relative to the cornea, when the lens wearer blinks, for example. Therefore, the contact lens of this mode of the invention enables to decrease or moderate discomfort as felt by the lens wearer due to friction between the contact lens and eyelid and/or cornea caused by the displacement of the contact lens relative to the cornea. Further, since a clearance between the back surface of the contact lens and the cornea is narrowed at a radially outward portion of the central zone, unfavorable entrance of the dust or contaminants accompanied with a circulation of the tear fluid may be prevented or limited.
With the contact lens of this mode of the invention worn on the cornea, the protrusion formed at the periphery of the central zone is pressed onto the surface of the cornea upon application of an external pressing force on a front surface of the contact lens. Such an external pressing force is applied on the front surface of the contact lens, by the eyelids of the lens wearer, when the lens wearer blinks, for example. As a result, the back surface of the contact lens is located adjacent to the surface of the cornea as close as possible, making it possible to restrict the displacement of the contact lens relative to the cornea. In this respect, the presence of the protrusion does not adversely effect on optical characteristics of the
Miyamura Kazuya
Sawano Tadashi
Sugimoto Keiji
Collins Darryl J.
Menicon Co. Ltd.
Rossi & Associates
Sugarman Scott J.
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