Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2002-11-29
2004-04-27
Sugarman, Scott J. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S177000
Reexamination Certificate
active
06726323
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Application No. 2001-367231 filed on Nov. 30, 2001, and No. 2002-341644 filed on Nov. 26, 2002, each including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a contact lens and a method of designing the same, and is concerned with techniques for providing a contact lens that is satisfactory in shape stability and that is thin and comfortable to wear. More particularly, the present invention is concerned with a novelly shaped contact lens suitably applicable to soft contact lenses, and capable of establishing an easiness of handling and an easiness of differentiating between a front surface and a back surface thereof with the help of its shape stability, while ensuring its suitable wearing comfort as felt by a lens wearer. The present invention is also concerned with a novel method of designing the contact lens.
2. Description of the Related Art
Generally, contact lenses require to be excellent in (a) lens wearing comfort as felt by a lens wearer, and to be easy of (b) handling by fingers of the lens wearer. In order to improve the former requirement, i.e., the lens wearing comfort, it is desirable to sufficiently reduce a thickness of a contact lens (hereinafter referred to as a “lens thickness” where appropriate) while assuring a minimum lens thickness determined by a selected lens material, with production efficiency and durability of the contact lens taken into consideration. Such a thin contact lens is also excellent in oxygen permeability. The thin contact lens, however, may be deteriorated in its shape stability. In the case of a thin soft contact lens, particularly, it is likely that the soft contact lens, when being placed on a finger of the lens wearer to be worn on or removed from a cornea, clings to a surface of the finger of the lens wearer. This makes it difficult to handle the contact lens by the fingers and to differentiate between a front surface and a back surface of the contact lens, resulting in cumbersome operations in wearing and removal of the contact lens.
To cope with these problems, a number of solutions have been suggested. For instance, a lens thickness of a contact lens is increased by an amount enough to ensure a good handling thereof based on its good shape stability. Alternatively, an identification mark is provided on a surface of the contact lens for allowing the wearer to differentiate between the front surface and the back surface of the contact lens. The latter one enables the contact lens to be made thin with a great regard for the lens wearing comfort, while coping with the problem of insufficiency in the shape stability of the contact lens. However, these solutions are still in a level of compromises in which any one of the wearing comfort and the shape stability (or the handling of the contact lens) is sacrificed or ignored, and are not what can be called fundamental solutions. In particular, a number of specific manufacturing process and workings are needed to form the identification mark on the surface of the contact lens, undesirably pushing a manufacturing cost.
In order to achieve both of the excellent lens wearing comfort and the good handling of the contact lens, JP-A-8-286155 discloses a contact lens design wherein a peripheral zone has a lens thickness of not less than 1.2 times a lens thickness as measured at a central portion of the lens, and a front junction of an optical zone with a peripheral zone on a front surface (or a front curve surface) of the lens is offset radially outwardly from a back junction of an optical zone with a peripheral zone on a back surface (or a base curve surface) of the lens, so as to increase the thickness of the peripheral zone. Further, JP-A-11-52304 and JP-A-2000-214417 disclose another contact lens design wherein there are determined a lens thickness as measured at its central portion and a lens thickness at and a position of a part of a peripheral portion where the thickness dimension is maximized.
These contact lens designs disclosed in the above-indicated documents are unsatisfactory in achieving both of the lens wearing comfort and good handling of the contact lens. In this respect, these conventional contact lens designs are basically concerned with the lens thickness as measured at around the front junction on the front surface of the contact lens where the optical zone and the peripheral zone join together, and determine the lens thickness at around the front junction to be made larger enough to exhibit its good shape stability, but not cause considerable deterioration of the lens wearing comfort as felt by the wearer. The increase in the lens thickness at around the front junction inevitably restricts a design of optical characteristics of the optical zone, resulting in a relatively low degree of freedom in designing lens forms and powers.
Upon designing a contact lens, generally, a radius of curvature of a back surface of the lens is determined as a base curve to approximately correspond to a shape of a surface of the cornea of the lens wearer so that the contact lens is comfortable to wear and is positioned on the cornea with high stability. Then, a front surface of the lens is designed so as to give a desirable optical power to an optical zone of the lens, and so as to permit the optical zone to have a minimum thickness of the lens determined by selected materials. Since the lens thickness as measured at around an outer peripheral portion of a front optical zone of the contact lens is dimensioned to a specific value, according to the above-described documents, the thickness of the optical zone is entirely restricted or affected by the thickness of the outer peripheral portion of the optical zone, thus limiting a degree of freedom in designing the contact lens and a power of the lens.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a contact lens which is novel in configuration and which is capable of highly ensuring both of lens wearing comfort and shape stability, while providing a high degree of freedom in designing the contact lens.
It is another object of the present invention to provide a novel method of designing such a contact lens.
The above and/or optical objects of this invention may be attained according to at least one of the following modes of the invention. Each of those modes of the invention is numbered like the, appended claims and depending 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 these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A contact lens comprising: a central optical zone including a front optical zone and a back optical zone; and a peripheral zone surrounding the optical zone and including a front peripheral zone and a back peripheral zone, wherein the contact lens is provided with a dioptric power P ranging from −10 to 0 diopters (−10≦P≦0), wherein the front optical zone and the front peripheral zone join together at a front junction, and the back optical zone and the back peripheral zone join together at a back junction that is located outward of the front junction in a diametric direction of the contact lens orthogonal to a center axis of the contact lens, and wherein the contact lens has a central lens thickness T
C
ranging from 0.03 to 0.50 mm as measured along the center axis thereof, a front junction lens thickness T
FJ
of not less than 0.05 mm as measured at the front junction, and a back-junction lens thickness T
BJ
as measured at the back junction, the back-junction
Kondo Kiyosei
Kouzai Arata
Miyamura Kazuya
Sawano Tadashi
Beyer Weaver & Thomas LLP
Menicon Co. Ltd.
Sugarman Scott J.
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