GB2114926A

GB2114926A - Method of manufacturing a multifocal contact lens

Info

Publication number: GB2114926A
Application number: GB08215353A
Authority: GB
Inventors: Akimichi Tsukamoto
Original assignee: Hoya Lens Corp
Current assignee: Hoya Lens Corp
Priority date: 1982-02-15
Filing date: 1982-05-26
Publication date: 1983-09-01
Also published as: JPS58143949A; AU8410582A; CH658732A5; KR850001081B1; BR8203072A; DE3219585A1; PH20839A; GB2114926B; JPS6147657B2; AU537795B2; KR830009903A

Abstract

A method of manufacturing a multifocal contact lens, in which a protective film 2 is bonded to a part of a spherical contact lens 4, the lens is polished to finish the lens surface other than the part covered with the protective film to a desired power, and the protective film is removed. The process is repeated at least once thereby manufacturing a multifocal contact lens suitable for each wearer. <IMAGE>

Description

SPECIFICATION Method of manufacturing a multifocal contact lens The present invention relates to a simple method of manufacturing a bifocal, a trifocal, or multifocal contact lens.

There have been known two conventional methods of manufacturing a bifocal contact lens.

In one of the methods, the near vision part of a contact lens is ground off and a material of different refractive power is bonded onto the ground-off part, followed by cutting and polishing the concave and convex sides of the contact lens to have an identical radius of curvature with each other. In the other method, a part of the concave or convex side of a contact lens made of a single kind of material is finished by polishing so as to have a radius of curvature different from that of the remaining part thereby forming parts of different refractive power.

The former method is troublesome in that two kinds of materials to be bonded to each other are required on one hand, and that a high skill is required for production on the other hand. In the latter method in which a spherical surface having two or more different radii of curvature is formed in a single lens. Therefore, it has been required to change the radius of curvature and the center of cutting revolution during the cutting process of the lens or it is required to form concentric parts of different radii of curvature in the lens. The latter method requires the respective cutting and polishing operations which are executed in two steps separately for a near vision and a distant vision part, thus resulting in the disadvantages of high accuracy required in manufacture and a low yield.

It is an object of the present invention to provide a simple method of manufacturing a multifocal contact lens obviating the above mentioned disadvantages of the conventional methods.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings, in which: Fig. 1 is a diagram for explaining a spherical surface contact lens having a part of a power for near vision required for the wearer.

Fig. 2 is a diagram for explaining a spherical contact lens with a prism having a near vision power required for the wearer.

Fig. 3 is a diagram for explaining the shape and arrangement of a protective film used in an embodiment of the present invention.

Fig. 4 is a diagram for explaining a polisher and a special jig used for the present invention.

Fig. 5 is a diagram for explaining a part of the special jig used for the present invention.

Fig. 6 is a diagram showing the steps of manufacturing a trifocal contact lens according to the present invention.

First, a spherical lens is manufactured by an ordinary method. Fig. 1 shows a spherical contact lens 1 having a power for near vision required for the wearer, and Fig. 2 shows a spherical contact lens with a prism 2 having a near vision power required for the wearer. In order to prevent the lens from rotating during wearing, the spherical contact lens with a prism 2 is more desirable. The near vision power of the wearer is measured in advance, the contact lens with a spherical contact lens with a prism 2 having the near vision power is worn by the wearer, the stable position of the contact lens worn is confirmed, and then the layout of the near vision part is designed. That is, the position taken by the near vision part in the contact lens and the shape and size thereof are determined.The contact lens is taken off, and a protective film of the same shape as the near vision part thus designed is attached to the convex surface of the contact lens. The protective film is such that an adhesive tape or adhesive film which neither hampers the correction of the power nor is peeled off nor broken during the polishing process is cut to an appropriate shape and size. As an alternative, a protective film may be sticked on the contact lens with a bonding agent or a protective coating film may be formed on the contact lens according to the layout. In any case, these materials must neither hamper the correction of the power nor peel off nor break. In Fig. 3, the hatched part shows the part on which the protective film 3 according to an embodiment of the present invention is to be sticked, the remaining part showing a distant vision part 4 of various shapes.The protective film 3 is required to be of such a nature that it can be taken off without damaging the surface of the contact lens after correction of the power.

Fig. 4 shows a polisher and a jig 6 used for correction of the power with an abrasive soaked in the sponge 5, and two methods of power correction.

In the method (A), in order to increase the power negatively, the contact lens is pressed against the sponge 5 while being polished in such a manner that the tangent line of the front curve of the lens is in parallel contact with the surface of the rotating cylinder of the polisher.

According to the method (B), in order to increase the plus power, the contact lens is pressed against the sponge 5 while being polished in such a manner that the front curve of the contact lens is in inclined contact with the surface of the rotating cylinder of the polisher.

After applying the protective film 3 to the contact lens, the convex side of the contact lens is polished by the method (A) or (B) with the concave side thereof applied to the jig to attain the desired power for distant vision. If a through-hole is formed at the center of the front part A of the jig 6, the through-hole is convenient for checking the power of the contact lens by the way of the polishing process of the lens. After correcting the power to the desired power, the protective film 3 is removed and the contact lens is washed. The part of the lens left by the protective film 3 maintains the original power of the spherical contact lens 1 or 2 and may be used as a near vision part.

Fig. 5 shows a diagram for explaining the special jig 6 used for fixing the contact lens to be polished in order to correct the power thereof. The feature of this special jig 6 is that the through-hole formed at the center of the front part A permits the power to be measured without taking off the contact lens 1 or 2 from the jig 6 by the way of the power correction process, and thus the power is capable of being confirmed through the hole.

The part other than that covered with the protective film 3 or which the power is corrected, may be used also for the distant vision purpose.

First, the stationary position of the lens with a prism is determined and remains substantially unchanged after correction of the distant vision power. Thus a bifocal lens suitable for the wearer involved is completed.

Fig. 6 shows the steps of manufacturing a trifocal contact lens by a simple method according to the present invention.

Fig. 6(a) shows the step of designing the intermediate and near vision parts most suitable for the wearer, of a spherical contact lens 1 or a spherical contact lens with a prism 2 having a near vision power required for the wearer. Fig. 6(b) shows the step of covering the protective film 3 only on the near vision part and correcting the power to a predetermined intermediate power by the polishing method mentioned above. Fig. 6(c) shows the step of correcting the power of the distant vision part of the lens with a protective film covered on the intermediate part while the protective film remains covered also on the near vision part. Fig: 6(d) shows the steps of confirming that the desired power has been attained, removing the protective film 3, and washing the lens.

By repeating the above-mentiQned method of the present invention, it is feasible to manufacture a multifocal contact lens. Although the foregoing description concerns the correction of a near vision power of a contact lens for a distant vision power, the present invention may be applied with equal effect to the case in which a contact lens having a distant vision power may be converted into a near vision power with use of protective film formed on the contact lens. Also, the concave side instead of the convex side may be processed in a similar manner with equal effect.

The method of manufacturing a multifocal contact lens according to the present invention is much simpler than the prior art methods and facilitates the manufacture of a multifocal contact lens suitable for each wearer thereby greatly contributing to the industry.

Claims

1. A method of manufacturing a multifocal contact lens comprising the steps of: a) bonding a protective film to a part of a spherical contact lens; b) polishing said contact lens, thereby to finish the lens surface other than the part covered by said protective film to a desired power; c) taking off said protective film; and d) repeating said steps at least once.

2. A method of manufacturing a multifocal contact lens according to Claim 1 , wherein said step of polishing the lens surface other than the part covered by said protective film to a desired power comprises the steps of: a) pressing said contact lens against a sponge of a polisher while polishing the same in such a manner that the tangent line of the front curve of said contact lens is in parallel contact with the surface of the rotating cylinder of said polisher, thereby to increase a minus power; and b) pressing said contact lens against said sponge while polishing the same in such a manner that the tangent line of the front curve of said contact lens is in inclined contact with the contact surface of said rotating cylinder of said polisher, thereby to increase a plus power.

3. A method of manufacturing a multifocal contact lens according to Claim 1, wherein said step of polishing the contact lens to a desired power uses a special jig with a through-hole formed at the center of a front part of said special jig thereby enabling the power to be confirmed through said hole without removin,g said lens from said special jig by the way of the polishing process.

4. A method of manufacturing a multifocal contact lens substantially as hereinbefore described with reference to the accompanying drawings.