GB2082957A - An Improved Method of Making Bifocal Contact Lenses - Google Patents
An Improved Method of Making Bifocal Contact Lenses Download PDFInfo
- Publication number
- GB2082957A GB2082957A GB8023499A GB8023499A GB2082957A GB 2082957 A GB2082957 A GB 2082957A GB 8023499 A GB8023499 A GB 8023499A GB 8023499 A GB8023499 A GB 8023499A GB 2082957 A GB2082957 A GB 2082957A
- Authority
- GB
- United Kingdom
- Prior art keywords
- lens
- prism
- mold
- cut
- resinous
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00932—Combined cutting and grinding thereof
- B29D11/00942—Combined cutting and grinding thereof where the lens material is mounted in a support for mounting onto a cutting device, e.g. a lathe, and where the support is of machinable material, e.g. plastics
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00009—Production of simple or compound lenses
- B29D11/00028—Bifocal lenses; Multifocal lenses
Landscapes
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Ophthalmology & Optometry (AREA)
- Mechanical Engineering (AREA)
- Eyeglasses (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
Abstract
A method of making bifocal contact lenses of a polymerised material in which one finished optical surface is moulded, a second optical surface is cut and polished whilst rotating the lens eccentrically to provide a lens having a relatively thin apex and a thicker base, the polished surface is covered with a protective layer of polymer and the lens again rotated eccentrically with the positions of the lens apex and base transposed to cut a further optical surface before removing the protective layer.
Description
SPECIFICATION
An Improved Method of Making Bifocal
Contact Lenses
Continuation-in-part of application Serial No.
972,526, entitled: A Method of Making Bifocal
Contact Lenses, which is a Continuation-in-part of Serial No. 874,934, filed February 3, 1978, entitled: A Method of Controlling the Adhesion of a Molded Plastics Lens, which is a Continuationin-part of application Serial No. 793,388, filed
May 25, 1977, now abandoned, entitled: A
Method of Making High Quality Plastic Lenses.
Background of the Invention
The use of plastic materials for making optical lenses has increased rapidly for the past ten years.
This is due to the availability of better plastic materials and the physical advantages of the plastic resins for specific applications such and contact lenses. The technology for the production of high quality contact lenses has not kept pace with the material supply industry. It is important to advance both areas if the full potential is to be realized.
The current lens molds are fabricated from glass, each mold is individually ground and polished to the required specifications. To achieve accurate reproduction of the bifocal molds is most difficult and expensive. This new process makes possible exact reproductions and has many other distinct advantages which will become apparent from the following disclosure.
An object is to provide a process for making inexpensive bifocal contact lenses which may be made to identical specifications.
Description of the Drawings
Fig. 1 shows the lens on the lathe with the distant power cut and the protective layer in place.
Fig. 2 shows lens replaced on the lathe and the near segment cut, in section.
Fig. 3 shows the finished lens from the front.
Fig. 4 shows the lens as in Fig. 1 from the front.
Fig. 5 shows the lens as in Fig. 2 from the front.
The Lenses are Made as Follows
A master positive mold having the curvature required on the concave surface of the finished lens is made from glass, stainless steel or other materials which withstand the molding pressures and temperatures. Materials which may be electroplated or plated by vacuum disposition have also been used.
The master positive mold is placed in a sleeve, a molding grade of a resinous material such as polyimide, polycarbonate, polymethylpentene, polyethylene, polypropylene, or other heat softened molding material is also placed in the sleeve. The sleeve and it's continents are heated to the softening point of the molding material, pressure is applied to form the negative lens mold. The sides of the master mold have been cut to a smaller diameter than the sleeve to provide an opening around the mold. When sufficient heat and pressure have been applied the molding compound will fill the area around the positive mold forming a cup-like cavity with a curved optical surface at the bottom. Either injection or compression molding may be used to produce the negative resinous mold.A liquid or syrup monomer material containing a suitable catalyst is placed over the optical surface of the mold and covered to prevent evaporation of the monomer.
The liquid monomer is polymerized within the mold to form a solid monomithic mass. Ultraviolet light, microwave energy or heat may be used to speed the polymerization process. Thermosetting and crosslinked hard materials may be used to produce lenses which are very dimensionally stable and could not be made by injection or compression molding. This process is also suitable for the production of soft contact lenses made from Hydroxethyl Methacrylate which cannot be made by compression or injection molding techniques.
It is not necessary to remove the hardened plastic lens material from the mold before cutting the convex bifocal curve. The mold, which is the arbor with the lens mounted, may be placed in a suitable lathe or grinding machine and the convex bifocal curvature cut and polished. A lathe with an off center eccentric male taper, 2 Fig. 1, is used to cut the distant convex refractive power curve, 5 Fig. 1,2, 3. 4 and 5. The concave curve, 6 Fig. 1 and 2, may be molded or cut and polished by methods well known to the art. The taper, 2 Fig.
1, is offset from the center of rotation, 1 Fig. 1, 2, 4 and 5, to produce a prism lens having a thin apex, 10 Fig. 1, and a thick base, 9 Fig. 1. The distant optical surface,6 Fig. 1, is polished and coated with a layer of polymer, 11 Fig. 1, to protect the polished surface and provide a smooth uninterrupted surface for polishing the shorter reading segment radius, 7 Fig. 2. Color may be added to the polymer coating to make the reading segment more visible during the cutting operation. The lathe radius is changed to cut the shorter radius of the near refractive curve, 7 Fig.
2, 3, and 5. The bifocal near refractive curve is cut leaving a rim at the periphery, 8 Fig. 2 and 3, to provide sufficient edge thickness to prevent the near segment from sliding beneath the lower lid in the reading position. With downward gaze, the lower lid will intersect the thick lower edge of the lens and displace the lens upward and move the reading segment into the visual axis. The thick lower edge also provides the ballast to prevent rotations and to keep the near refractive segment at the bottom. When cutting the near segment the protective polymer layer, 11 Fig. 2, is cut away exposing the lens material in the reading segment area. The protective layer is thick enough to provide a continuous uninterrupted surface, 7 Fig. 2, whereby the polishing is achieved in the conventional method well known to the art.The polymer, 11 Fig. 1, is selected from the acrylics, epoxies, polyesters, or cellulosics. It is understood that the process may be reversed
and the distant lens power made without prism or
offset and the reading segment cut with prism or
offset or the combination of prism and offset in
both distant or near segments may be employed.
Stabilization may be achieved or enhanced by the
use of prism ballast, truncation inferiorly, truncation superiorly, thinning of the upper edge, thinning of the lower edge, thinning of both upper
and lower edges, cutting horizontal groves near the upper edge on the convex surface of the lens,
cutting vertical groves near the upper edge on the convex surface of the lens, placing holes or slots
near the upper edge of the lens. 1 2 Fig. 3, shows a grove cut on the convex surface near the upper edge. These procedures function due to the fact that the upper lid moves basically vertically during the blink and the lower lid moves basically horizontally during the blink. Truncation is usually employed to aid in stabilization of the lens.Lenses are well tolerated in the eye as the thick edge remains at the bottom and the lower lid moves horizontal on the blink cycle. The finished lens now has a molded concave surface and a convex bifocal curvature which was cut and polished without being removed from the disposable mold.
The mold has served as a container for the monomer and provided the molded optical surface, which may be aspheric, toric or may be composed of two or more spherical segments.
The cup-like mold also serves as the holding block to facilitate cutting to the required thickness. The thickness of the cup bottom may be measured before adding the liquid monomer and measurements may be taken during the cutting operation and the lens thickness determined by subtracting the thickness of the cup bottom. The mold also serves as a holding fixture during the polishing operation. The lens is supported by the optical surface present on the mold; therefore, the lens material must adhere strongly to the supporting mold in order to withstand the forces of cutting and polishing.
After the lens is processed to the required
specifications, the lens is removed by heating the
resinous holding fixture to slightly soften the
resinous mold material but not softening the
crosslinked cast lens material. The heat softened
mold is flexed by applying pressure, distorting and
stretching the surface of the softened material
away from the hard rigid lens material, separating
the finished optical lens from its support.
Various modifications can be made without
departing from the spirit of this invention or the
scope of the appended claims. The constants set
forth in this disclosure are given as examples and
are in no way final or binding. In view of the
above, it will be seen that the several objects of
the invention are achieved and other advantages
are obtained. As many changes could be made in
the above constructions and methods without
departing from the scope of the invention, it is
intended that all matter contained in the above
description shall be interpreted as illustrative and
not in a limiting sense.
Claims (9)
1. A method of making a bifocal lens comprising the steps of: Providing a positive lens mold having a first surface curvature corresponding to the curve required on one surface of the finished lens, and a second surface corresponding to the edge surface of the finished lens with the second surface extending from the first surface curvature a distance greater than the height of the thickness of the lens, forming a negative mold from the positive mold by applying a softened resinous material against the first surface curvature and the second surface of the positive mold to form an open top cylinder from the resinous material with an image of the first surface curvature as the bottom of the cylinder and the image of the second surface as the walls' of the cylinder, removing the positive lens mold from the negative lens mold, filling the resinous cylinder of the negative mold with a liquid monomer lens material allowing the liquid monomer lens material to polymerize to form a solid monolithic mass within the resinous cylinder of the negative mold having one finished optical surface molded by the negative image of the first surface curvature formed in the bottom of the resinous cylinder, providing an eccentric rotation while cutting and polishing a second optical surface on the polymerized lens material, to produce a prism lens having a thin apex and thicker base, while the lens material is supported within the resinous cylinder, covering the polished surface of the prism lens with a protective layer of polymer material placing the lens a second time upon the eccentric with the thin apex positioned at the same location that the thicker base was positioned the first time, and the second position of the thick base being the same as the first position of the thin apex, cutting a third optical surface having a selected radius shorter than the second radius, polishing the third radius, removing the lens from the resinous cylinder of the negative mold and removing the protective polymer layer.
2. A method as in Claim 1, wherein the resinous mold is heated before removing the iens.
3. A method as in Claim 1 , wherein the first surface is cut having no prism and second surface is cut having prism.
4. A method as in Claim 1, wherein the first surface is cut having prism present and the second surface is cut having no prism.
5. A method of preventing rotation of a bifocal contact lens while on the eye by providing a depression in the convex lens surface, the depression being positioned near the intended upper edge of the lens, whereby the blinking movement of the upper eye lid will position the depression at the upper rotational position.
6. A method of making bifocal lenses by the steps of providing an eccentric rotation while cutting and polishing a first optical surface on the polymerized lens material, to produce a prism lens having a thin apex and a thicker base, covering the polished surface of the prism lens with a protective layer of polymer material placing the lens, a second time upon the eccentric with the apex positioned at the same location that the thicker base was positioned the first time, and the second position of the thick base being the same as the first position of the thin apex, cutting a second optical surface having a selected radius shorter than the first radius, polishing the second radius, removing the protective polymer layer from the lens.
7. A method as in Claim 6, wherein the first surface is cut having no prism and the second surface is cut having prism.
8. A method as in Claim 6, wherein the first surface is cut having prism present and the second surface is cut having no prism.
9. A method of making a bifocal lens substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8023499A GB2082957A (en) | 1980-07-18 | 1980-07-18 | An Improved Method of Making Bifocal Contact Lenses |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8023499A GB2082957A (en) | 1980-07-18 | 1980-07-18 | An Improved Method of Making Bifocal Contact Lenses |
Publications (1)
Publication Number | Publication Date |
---|---|
GB2082957A true GB2082957A (en) | 1982-03-17 |
Family
ID=10514857
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB8023499A Withdrawn GB2082957A (en) | 1980-07-18 | 1980-07-18 | An Improved Method of Making Bifocal Contact Lenses |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2082957A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0942311A1 (en) * | 1998-03-09 | 1999-09-15 | Menicon Co., Ltd. | Prism ballast type contact lens, method of producing the same, and mold assembly used in producing the lens |
US6316725B1 (en) | 1998-12-14 | 2001-11-13 | Walker Systems, Inc. | Housings for underfloor raceways |
WO2015114339A1 (en) * | 2014-01-30 | 2015-08-06 | Sauflon Cl Limited | Method of making contact lenses |
-
1980
- 1980-07-18 GB GB8023499A patent/GB2082957A/en not_active Withdrawn
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0942311A1 (en) * | 1998-03-09 | 1999-09-15 | Menicon Co., Ltd. | Prism ballast type contact lens, method of producing the same, and mold assembly used in producing the lens |
US6158861A (en) * | 1998-03-09 | 2000-12-12 | Menicon Co., Ltd. | Prism ballast type contact lens, method of producing the same, and mold assembly used in producing the lens |
US6316725B1 (en) | 1998-12-14 | 2001-11-13 | Walker Systems, Inc. | Housings for underfloor raceways |
USRE40069E1 (en) | 1998-12-14 | 2008-02-19 | The Wiremold Company | Housings for underfloor raceways |
WO2015114339A1 (en) * | 2014-01-30 | 2015-08-06 | Sauflon Cl Limited | Method of making contact lenses |
US10363711B2 (en) | 2014-01-30 | 2019-07-30 | Coopervision International Holding Company, Lp | Method of making contact lenses |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |