Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2002-01-24
2003-12-09
Sugarman, Scott J. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S161000
Reexamination Certificate
active
06659607
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Application No. 2001-022088 filed on Jan. 30, 2001, and No. 2001-375469 filed on Dec. 10, 2001 including the specification, drawings and abstract are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to contact lens to be worn on a cornea of a human eye, which has a substantially circular optical zone and an annular peripheral zone disposed around the optical zone. More particularly, the present invention is concerned with such a contact lens, which is novel in construction and which is capable of enhancing lens wearing comfort as felt by a lens wearer.
2. Description of the Related Art
There is known a contact lens which 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, there is a great need to enhance lens wearing comfort as felt by the lens wearer.
In general, the contact lens includes a substantially circular central optical zone serving for transmitting light to a pupil, and an annular peripheral zone disposed radially outwardly of the optical zone and serving for placing the contact lens on a predetermined position on the cornea. The peripheral zone is designed to permit a good circulation of tear fluid existing between the cornea and the contact lens. The optical zone has a back surface that is formed in a concave shape whose curvature is made substantially equal to that of the cornea of the lens wearer, so that the back surface of the optical zone of the contact lens may suitably fit the shape of the cornea of the lens wearer. This radius of curvature of the back surface of the optical zone of the lens is generally referred to as a base curve.
However, the 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 type 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 significantly 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 portion 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 comprising: (a) an optical zone having a generally circular shape; (b) an peripheral zone having a generally annular shape and located around the optical zone; and (c) an intermediate zone having a generally annular shape and interposed between the optical and peripheral zones, wherein the intermediate zone has a back surface provided with a convex portion formed in at least one diametrical position thereof and extending in a circumferential direction thereof with an outwardly curved surface in cross section taken in a plane parallel to a diametric direction of the contact lens.
In the contact lens according to this mode of the invention, the convex portion is disposed radially outwardly of the optical zone and extends in the circumferential direction of the contact lens so as to surround the optical zone. With the contact lens worn on a cornea of a lens wearer, this convex portion protrudes toward the cornea from a posterior surface of the contact lens, and is located closely adjacent to a surface of the cornea. A tear fluid layer existing between the posterior surface of the contact lens and the cornea is partially narrowed and restricted at a portion where the convex portion is opposed to the cornea. Therefore, the convex portion smoothly leads the posterior surface of the contact lens to be located adjacent to and positioned relative to the surface of the cornea with its smooth outwardly curved surface having no peak or junction.
Accordingly, the contact lens of the invention permits an improved lens wearing comfort as felt by the lens wearer. In addition, since the convex portion partially narrows the tear fluid layer, unfavorable entrance of dusts or other floating objects in the atmosphere into the tear fluid layer is effectively restricted or limited, 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 limitation of the entrance of the dusts into the tear fluid layer, stem from the following technical basis or reasons: (i) a barrier effect owing to a convex configuration of an alignment portion (that is contact with or most closely adjacent to the surface of the cornea) of the contact lens, i.e., the convex portion formed in the back surface of the intermediate zone that is opposed to and protrudes toward the surface of the cornea; and (ii) a stress diffusion effect owing to the outwardly curved surface of the convex portion of the intermediate zone, which permits the convex portion to be opposed to the surface of the corneal with a smooth surface.
A result of extensive research and study of the inventors reveals that the contact lens of this mode of the invention exhibits a high positioning stability on the cornea, while ensuring a reduced 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, resulting in further improved lens wearing comfort as felt by the lens wearer. This improvement of the lens wearing comfort may also stem from that the limited entrance of the dusts or other floating objects into a clearance between the contact lens and the cornea via the tear fluid existing and circulated between the contact lens and the cornea due to the presence of the narrowed portion of the tear fluid layer, as well as the above-indicated reduced displacement of the contact lens relative to the cornea.
Described more specifically, the contact lens of this mode of the invention is worn on the cornea and pressed onto the cornea upon application of an external pressing force thereon. Such an external pressing force is applied on an anterior surface of the contact lens, by the eyelids of the lens wearer, when the lens wearer blinks. As a result, the posterior surface of the contact lens is loc
Kondo Hideaki
Miyamura Kazuya
Nagai Shigeyasu
Sawano Tadashi
Sugimoto Keiji
Collins Darryl J.
Menicon Co. Ltd.
Rossi & Associates
Sugarman Scott J.
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