JP2003015094A - Hard contact lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact lens for vision correction which is adaptable to keratoconus of all symptoms including light, middle and heavy degrees by stepwise changing the differences in the curvature of the regions of a central segment and peripheral segments of the contact lens having multistage curves at specific ratios and is usable comfortably for a long time. SOLUTION: The curved surfaces of the contact lens 1 of which the rear face on the side in contact with the cornea comprises different curved surfaces have the different four regions including the one central part 2 and the three peripheral parts 3, 4 and 5. The widths of the three regions of the peripheral segments are respectively 0.5 mm and when the differences in the curvature of both regions adjacent toward the peripheral parts 3, 4 and 5 from the central part 2 of the respective regions are compared, these differences have the relations of about the middle difference to about the small difference then to about the large difference successively from the segments nearer the central segment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard contact lens having a curved rear surface which is a side in contact with a cornea. More specifically, the present invention relates to a hard contact lens for keratoconus in which the curvature of the back curved surface of the hard contact lens is changed stepwise at a specific rate.

[0002]

2. Description of the Related Art A keratoconus has a corneal shape in which a central portion corresponding to a cone is steep and gradually becomes flat toward the peripheral portion. Conventionally, a two-point contact method or a three-point contact method using a spherical hard contact lens has been generally used as one of the visual acuity correction methods for keratoconus patients. However, in this method, the corneal epithelial lesion at the apex of the cone occurs and the stability of the lens is poor. Further, there are various problems such as poor wearing feeling.

In order to improve the feeling of wearing, there is a method of using a lens in which a hard contact lens is fitted in a soft contact lens, but the handling is complicated, the soft contact lens does not fit the keratoconus, and the hard contact lens does not fit. There is a drawback that many lenses come off.

Further, conventionally, an aspherical contact lens in which the inner surface side of the contact lens has a corneal shape is generally known. For example, JP-A-56-106217
No. 10-23964, in which the inner surface shape of the contact lens is changed according to the shape of the cornea.
No. 0 discloses a contact lens in which the central portion and the peripheral portion of the inner surface are formed with different curved surfaces, and then the spherical portion and the aspherical portion are combined according to the corneal shape. further,
Contact lenses with multi-step curves are also commonly considered. However, in many existing multi-stage curved lenses, the difference between the curvature of the central part and the curvature of the peripheral part is constant for each lens. Couldn't respond to.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a contact lens having a multi-step curve, in which the difference in curvature between the central portion and the peripheral portion is changed stepwise at a specific rate to obtain a mild or moderate degree. Another object of the present invention is to provide a contact lens for vision correction which can be applied to keratoconus of all severe symptoms and can be comfortably used for a long time.

[0006]

In order to solve the above problems, the contact lens of the present invention is a contact lens in which the posterior surface, which is the side in contact with the cornea, is composed of different curved surfaces, and the curved surface has one central portion. Section and three peripheral portions having different four regions, and the widths of the three regions of the peripheral portion are 0.
Comparing the differences in curvature between the two regions that are 5 mm and are adjacent to each other from the central portion to the peripheral portion, the difference from the order closer to the central portion is to a medium difference → a small difference → a large difference. Characterized by being in a relationship. Further, the curvature difference of the medium difference is 0.7 to 1.1 mm, the curvature difference of the small difference is 0.5 to 0.6 mm, and the curvature difference of the large difference is It is 1.2 to 2.1 mm.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a contact lens having a posterior surface design capable of coping with all keratoconus symptoms, which is obtained by analyzing a cornea of a keratoconus patient by a topography image. That is, the present inventors, as a result of examining the data measured by the corneal topography device,
The three peripheral regions have a width of 0.5 mm, and the difference between the curvatures of the two regions that are adjacent to each other from the central part to the peripheral part is a medium difference from the one closer to the central part to a small degree. The present invention has been completed by finding that a contact lens having a posterior surface design having a relationship of a difference of ∘ and a large difference fits the keratoconus of each symptom.

Preferred embodiments of the contact lens of the present invention will be described below with reference to the drawings. The contact lens of the present invention may be any conventional methacrylic resin or oxygen permeable material as long as it is a hard contact lens. In the contact lens 1 shown in FIG. 1, the posterior surface which is the side in contact with the cornea has a center part 2 to a central part 2, an inner peripheral part 3 annularly formed around the central part 2, an intermediate peripheral part 4, and an outer peripheral part 5. It consists of The central portion 2 is a surface that contacts the central cornea of the keratoconus, the inner peripheral portion 3 and the intermediate peripheral portion 4 are portions that contact the peripheral cornea, and the outer peripheral portion 5 is a tear for promoting tear exchange. It is a part that forms a liquid pool, and each part has four different curvatures.

The central portion 2 is a portion for correcting visual acuity, the curvature thereof needs to be approximated to the curvature of the central cornea, and the area thereof is preferably 6 mm or more in diameter. In addition, the inner peripheral portion 3, the middle peripheral portion 4, and the outer peripheral portion 5
The widths of the three regions are all 0.5 mm, and it is necessary to provide the respective curvatures and the curvature of the central portion with a specific difference. That is, the central portion 2 and the inner peripheral portion 3
The curvature difference between the inner peripheral portion 3 and the intermediate peripheral portion 4 is small, and the difference between the intermediate peripheral portion 4 and the outer peripheral portion 5 is large. This is a feature of the present invention. The standard is as follows.

For example, No. In case of 1 lens,
When the curvature of the central portion 2 of the rear surface is 5.0, the curvature of the peripheral portion 3 on the inner side is 6.1, and if the difference between the two is medium,
It is shown that the difference between the inner peripheral portion 3 and the middle peripheral portion 4 is small, and the difference between the middle peripheral portion 4 and the outer peripheral portion 5 is large. Similarly, No. 2 to No. The curvature of the design of each area in 5 will also be set.

[0011]

[Table 1]

[0012]

According to the present invention, in order to correspond to a keratoconus having a peripheral corneal shape that is flatter than the central cornea, the posterior surface of the contact lens having a multi-step curve has a specific shape. Therefore, the hard contact lens of the present invention can be applied to keratoconus of all symptoms of mild, moderate and severe. In addition, since the curvature of the central part and the peripheral part is greatly changed, even if a prescription that causes a tear fluid pool at the apex of the cornea is made difficult to steep in the peripheral part, the apex of the cornea and the contact lens are provided in order to provide visual acuity. Since it does not hit strongly even if it is prescribed so as to come into contact with it, it can be used comfortably for a long time and can perform vision correction.

[Brief description of drawings]

FIG. 1 is a view showing a contact lens according to a preferred embodiment of the present invention, in which A is a sectional view and B is a front view.

[Explanation of symbols]

1 contact lens 2 Central part 3 Inner periphery 4 Middle area 5 Outer periphery

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Uno             Hongo 2-40-2, Bunkyo-ku, Tokyo Shi Corporation             In the cord F-term (reference) 2H006 BB02 BC03

Claims (2)

[Claims] 1. A contact lens comprising a curved surface having a different posterior surface, which is a side in contact with the cornea, wherein the curved surface has four different regions of one central portion and three peripheral portions, and the peripheral portion. The width of each of the three regions is 0.5 mm, and the differences in curvature between the two regions that are adjacent to each other from the central portion to the peripheral portion of each region are compared. A contact lens characterized by a relationship of a small difference to a large difference. 2. The medium difference curvature difference is 0.7 to
1.1 mm, and the curvature difference of a small difference is 0.5 to
0.6 mm, and the difference in curvature of a large difference is 1.2 to
The contact lens according to claim 1, having a length of 2.1 mm.