CA1099546A - Contact lens - Google Patents
Contact lensInfo
- Publication number
- CA1099546A CA1099546A CA289,638A CA289638A CA1099546A CA 1099546 A CA1099546 A CA 1099546A CA 289638 A CA289638 A CA 289638A CA 1099546 A CA1099546 A CA 1099546A
- Authority
- CA
- Canada
- Prior art keywords
- lens
- methacrylate
- curve
- varies
- hydrogel
- 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.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
- G02C7/00—Optical parts
- G02C7/02—Lenses; Lens systems ; Methods of designing lenses
- G02C7/04—Contact lenses for the eyes
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K9/00—Medicinal preparations characterised by special physical form
- A61K9/20—Pills, tablets, discs, rods
- A61K9/2004—Excipients; Inactive ingredients
- A61K9/2022—Organic macromolecular compounds
- A61K9/2027—Organic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polyvinyl pyrrolidone, poly(meth)acrylates
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- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Physics & Mathematics (AREA)
- Ophthalmology & Optometry (AREA)
- Public Health (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- Epidemiology (AREA)
- Pharmacology & Pharmacy (AREA)
- Veterinary Medicine (AREA)
- Medicinal Chemistry (AREA)
- Chemical & Material Sciences (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Eyeglasses (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Materials For Medical Uses (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This invention concerns a minus prescription hydrogel contact lens that permits oxygen diffusion to the cornea in sufficient quantity to avoid the effects of oxygen deprivation;
avoids the physiological complications arising from damage to the bulbar conjunctivia due to compression of the limbal capil-laries; and avoids corneal scleral or wetting deficiences. These advantages are accomplished through a combination of lens design and hydrogel properties.
This invention concerns a minus prescription hydrogel contact lens that permits oxygen diffusion to the cornea in sufficient quantity to avoid the effects of oxygen deprivation;
avoids the physiological complications arising from damage to the bulbar conjunctivia due to compression of the limbal capil-laries; and avoids corneal scleral or wetting deficiences. These advantages are accomplished through a combination of lens design and hydrogel properties.
Description
$
- This invention relates to soft hydrogel contact lenses and more specifically, is directed to soft contact lens design.
As is known in the art, contact lenses are frequently made from polymethyl methacrylate. Such lenses are known as the "hard lenses". Many people cannot adapt to the presence of a hard lens in the eye and with others, the lens compromises the physiolo~ical processes required for corneal metabolism. More recently, new soft lens materials have been developed which avoid some o the problems associated with the hard lens. One class of such lens materials is described in U.S. Patents Nos. 2,976,576 and 3,220,960. These materials are hydrogels of a sparingly cross-linked hydrophilic co~olymer comprising a major amount of a monoester of an olefinic acid from the group of acrylic and methacrylic acids ha~ring a single olefinic double bond and a minor amount of polymerizable diester of one of said acids, the diester having at least two olefinic double bonds. A preferred hydrogel disclosed in the aforesaid ~atents is a slightly cross-linked material comprising a pre-dominant quantity of 2-hydroxyethyl methacrylate. The hydrogel, known as "hema", is used for contact lens fabrication because of its ability to absorb water of hydration, typically from about 35 to 65% by weight of the hydrogel. The water renders the lens flexible ar.d soft which properties enable it to mold to the curvature of the eye. This is in contrast to the conventional hard lens which maintains a rigid confiyuration that does not always conform to the eye's curvature.
In V.S. Patent No. 4,056,496, hydrogels are disclosed which are also suitable for soft lens fabrication. The hydrogels are formed from a hydrophilic monomer from the group of dihydroxy-alkyl acrylates and methacrylates, a substantially ~ater insol-uble monomer from the group of alkyl acrylates and methacrylates and preferably, a minor amount of an epoxidized alkyl acrylate ~9~s~
or methacrylate by a free radicaJ, bulk polymeri~ation process in the substantial absence oE solvent.
It is known in the art that the conventional hard contact lenses and many of the contemporary soft hydroyel lenses may only be worn for a short duration of time, typically Eor periods of time up to twelve hours. It is further known that extended wear, for periods in excess of -twelve hours, particularly during closed-eye periods (during sleeping hours) may cause long term injury to the eye.
Perhaps -the most serious cause of injury arisin~ from ~xtended wear of the aforesaid lenses is oxygen deprivation due to the lens covering a significant portion oE the corneal surface r~
thus acting as a barrier to contact of the cornea with an oxygenated tear layer. This results in oxygen deprivation at the cornea and interferes with the metabolic and physiological requirements of the cornea.
It is known that the cornea requires a supply of oxygen at its surface and relies upon oxygen diffusion from a tear layer over its surface for almost all of its required supply.
During open-eye periods, the tear layer is oxygenated by atmos-pheric oxycJen. During closed-eye periods, the tear layer is oxygenated by the capillaries of the eyelid rather than oxygen rom the atmosphere as when the eye is open. The partial pressure o oxygen supplied from the capillaries is less than about 1/3 that supplied by the atmosphere. In the absence of a lens acting as a barrier, -the oxygen supply to the cornea, both during ~ ~`
open-eye and closed-eye periods, is sufficient.
kh o w ~ r It is-~w~r~ that a contact lens capable of continuous wear should provide at least 3.5 I~l/cm -hr, preferably 6 1ll/cm2-hr of oxygen to the corneal surface to avoid the physiological complication arising from oxygen deprivation. ~lard contact lenses r such as -those of methyl methacrylate, are not permeable g~
to oxygen, but through known lens design, permit some circulation of ~ir to the corneal surEace. Contemporary hydrogel lenses, though permeable to oxygen through the interstitial sp~ces of the hydrogel material, are not sufficiently permeable to fully oxygenate the cornea in -the cross-sections in which they are fabricated. Hence, oxygen deprivation is also encountered with these lenses.
The circulation of some oxygen using the aforesaid lenses permits daily wear of the same with minimal non-reversible damage to corneal physiology. I~owever, during closed-eye periods when the oxygen supply is reduced to less than 1/3 the level of opened-eye condition, known lens design does not permit sufficient transfer of oxygen to the corneal surface to permit wear without oxygen deprivation.
For purposes of definition herein, the term "daily wear lens" and like terms are intended to mean a lens normally worn during open-eye periods but not during closed-eye periods (i.e., during periods of sleep.) The term "continuous wear lens" and like terms are intended to mean a lens tha-t may be worn as a daily wear lens if desired but which can also be worn for extended periods of time (i.e., both during open-eye and closed-eye~ periods), if desired.
It is an object of the invention -to provide a minus prescription hydrogel contact lens tha-t can be worn on a continuous or daily basis, if desired, withou-t removal from the eye, both during opened-eye and closed-eye periods without damage to the cornea.
Another object of this invention is to provide a hydrogel minus prescrip-tion contact lens which can be removed from the eye by the patient, handled and reinserted in the eye without damage to the lens.
A further object of this invention is to provide a hydro~el minus prescription contact lens capable of continuous wear which lens permits oxygen diffusion to the cornea in sufficient quantlty to avoid the adverse effects of oxygen deprivation; avoids physiological complications arising from damaqe to the bulbar conjunctivia due to compression of the lim-bal capi:Llaries; and avoids corneal-scleral wetting deficiencies.
~ n additional object of the invention is to provide a hydrogel minus prescription contac-t lens which conforms to -the shape of the eye.
The objec-ts of the invention are accomplished with a combination of design features and hydrogel properties that .~
enable fabrication of the lens in substantially reduced cross- '~i sectional thickness and mass (weight). In this respect, -the maximum cross-sectional thickness of the lens does not exceed 0.15 mm for a daily wear lens and 0.10 mm for a continuous wear lens. Other design features of the lens include a minimum dia-meter of at least 12 mm and preferably, ranging between 13 and 17 mm; a reduced posterior peripheral curve width not to exceed 1.5 mm and preferably, total elimination of all posterior peri-pheral curves so that the base curve is a monocurve that is smooth, uninterrupted and preferably spherical; an anterior lenticular curve preferably extending from the edge of the optical zone to the periphery of the lens and havi.ng a radius such that the edge thickness of the lens does not exceed 0.08 mm and preferably, does not exceed 0.06 r~m; and physical properties such that the lens is capable of handling and conforming -to the curvature of the eye, at least in the periphery of the lens.
The hydrogel used for lens constructi.on ls one capable of containing at least 35% water of hydration and must be sufficiently rigid so as -to maintain i-ts shape in -the required thin cross section while confo~ming to the eye. A preferred class of suitable ma-terials is disclosed in United States Patent ~,9~
No. 4,056,496 supra.
With reference to the drawing, there is shown a cross section of a hydrated minus soft lens fabricated in accordance with the mos-t preferred embodimen-t of the inven-tion.
The inner surface of the lens, frequently referred to as posterior surface, comprises base curve 1 having radius 2.
In accordance with this invention, -the base curve is preferably a monocurve -- i.e., the posterior surface of the lens is smooth and of a single radius. flowever, as is known in -the art, the base curve may be provided with one or more peripheral curves (not shown in the drawing), if desired, -though this is a lesser preferred embodiment. ~lowever, if present, the peripheral curve has a maximum band width of 1.5 mm and more preferably, a maximum of 1.0 mm.
The front surface of the lens, frequently referred to as the anterior surface, comprises power or prescription curve 3 having radius 4. The width of power curve 3 is known as the optical zone of the lens (defined between points 5 and 6 of the clrawing). This width is generally sufficient to cover most, preferably all, of the cornea and hence, usually varies between about 8 and 10 mm and more typically between 8 1/2 and 9 1/2 mm.
The anterior surface of the lens also is provided with lenticular curve 7 having radius 8. The lenticular curve extends from its junction with the optical curve to the outer periphery or ed~e of the lens.
The overall diameter or chord of the lens is defined as the distance between points 9 and 10. This diameter is at least 12 mm, preferably varies between 13 and 17 mm and most preferable is about 13.5 mm.
For daily wear, the lens has a maximum cross-sectional thickncss at any point on its circumference not exceeding 0.15 mm preferably not exceeding 0.10 mm and most preferably varying 5~
..~
between about 0.05 and 0.10 mm. For con-tinuous wear,the maximum cross-sectional thickness of the lens at any point on its cir-cumference does not exceed 0.10 mm, preferably does not exceed 0.08 mm and most preferably varies between about 0.03 and 0.08 mm.
The lenses of the subject invention are thinner than those of the prior art, and the reduced thickness represents departure from the prior art. The reduced cross-section permi-ts increased oxygen diffusion through the lens thus avoiding corneal swelling tha-t would otherwise result as a consequence of oxygen deprivation on the corneal surface for an extended period of time. In this respect, it should be noted that oxygen deprivation at the corneal surface is a serious problem while depriving the conjunctivia of ~r oxygen is not a problem since it receives oxygen from the vascular system. Ilence, though a lesser preferred embodiment of the invention, the cross-sec-tional thickness of the peripheral portion of the lens, beyond the optical zone of the lens, can be thicker ~$
than the remainder of the lens without seriously compromising corneal metabolism though it is preferred to maintain the overall cross-sec-tional thickness of the lens as small as possible as this reduces the mass of the lens that rests on the surface of the eye.
The edge of the lens is also of reduced cross-section and preferably edge thickness as defined between points 11 and 12 of the drawing varies between about 0.03 and 0.08 mm and more preferably, is about 0.06 mm. A reduced edge thickness within the limits set forth is desirable as the edge will not interfere with the eyelid with normal blinking and hence drying of the scleral tissue is minimized.
The radius 2 of base curve 3 is within prior art limits and is to some extent dependent upon the shape of the eye to which the lens is fitted. The radius 4 of the power curve 3 is also within the prior art and is dependent upon the correction provided by the lens. Finally, -the radius 8 of the lenticular ~i9~i~
~ curve 7 is that necessary to provide the desired edge thickness of the lens. The lenticular curve extends from its junction with the power curve to the outermost edge of the lens and to reduce edge thickness, the curve must be steeper than the power curve. Ilence, the radius 8 of the lenticular curve 7 is shorter than radius 4 of power curve 3. Preferably, radius 8 is at least 0.2 mm shorter than radius 4 and more preferably, a-t least `
0.5 mm. It should be noted that where the lenticular curve is steeper than the power curve and particularly, in the absence of posterior peripheral curvatures, the mass of the lens is substantially reduced.
The hydroyel used to fabricate the lens is one capable of retaining its struc-tural integrity in the thin cross-sections required for the lens, is sufficiently rigid to retain a sub-stantially constant optical surface and is sufficiently flexible to permit the lens to conform to the surface contour of the eye.
The ability to conform to the surface contour of the eye is most important as it is responsible for the lens remaining firmly affixed to the eye without substantial movemen-t and change in optical surface as is frequently encountered with blinking~
Preferably, the hydrogel has a water of hydration of a-t least 35~. and preferably a water of hydration varying between 35 and 50% and more preferably between 40 and 4S%.
Preferred hydrogels are a terpolymer of a hydrophilic dihydroxy acrylate, a water-insoluble acrylate and an epoxidized acrylate.
The hydrophilic dihydroxyalkyl acrylate comonomer conforms to the general formula:
R O Oll ll l
- This invention relates to soft hydrogel contact lenses and more specifically, is directed to soft contact lens design.
As is known in the art, contact lenses are frequently made from polymethyl methacrylate. Such lenses are known as the "hard lenses". Many people cannot adapt to the presence of a hard lens in the eye and with others, the lens compromises the physiolo~ical processes required for corneal metabolism. More recently, new soft lens materials have been developed which avoid some o the problems associated with the hard lens. One class of such lens materials is described in U.S. Patents Nos. 2,976,576 and 3,220,960. These materials are hydrogels of a sparingly cross-linked hydrophilic co~olymer comprising a major amount of a monoester of an olefinic acid from the group of acrylic and methacrylic acids ha~ring a single olefinic double bond and a minor amount of polymerizable diester of one of said acids, the diester having at least two olefinic double bonds. A preferred hydrogel disclosed in the aforesaid ~atents is a slightly cross-linked material comprising a pre-dominant quantity of 2-hydroxyethyl methacrylate. The hydrogel, known as "hema", is used for contact lens fabrication because of its ability to absorb water of hydration, typically from about 35 to 65% by weight of the hydrogel. The water renders the lens flexible ar.d soft which properties enable it to mold to the curvature of the eye. This is in contrast to the conventional hard lens which maintains a rigid confiyuration that does not always conform to the eye's curvature.
In V.S. Patent No. 4,056,496, hydrogels are disclosed which are also suitable for soft lens fabrication. The hydrogels are formed from a hydrophilic monomer from the group of dihydroxy-alkyl acrylates and methacrylates, a substantially ~ater insol-uble monomer from the group of alkyl acrylates and methacrylates and preferably, a minor amount of an epoxidized alkyl acrylate ~9~s~
or methacrylate by a free radicaJ, bulk polymeri~ation process in the substantial absence oE solvent.
It is known in the art that the conventional hard contact lenses and many of the contemporary soft hydroyel lenses may only be worn for a short duration of time, typically Eor periods of time up to twelve hours. It is further known that extended wear, for periods in excess of -twelve hours, particularly during closed-eye periods (during sleeping hours) may cause long term injury to the eye.
Perhaps -the most serious cause of injury arisin~ from ~xtended wear of the aforesaid lenses is oxygen deprivation due to the lens covering a significant portion oE the corneal surface r~
thus acting as a barrier to contact of the cornea with an oxygenated tear layer. This results in oxygen deprivation at the cornea and interferes with the metabolic and physiological requirements of the cornea.
It is known that the cornea requires a supply of oxygen at its surface and relies upon oxygen diffusion from a tear layer over its surface for almost all of its required supply.
During open-eye periods, the tear layer is oxygenated by atmos-pheric oxycJen. During closed-eye periods, the tear layer is oxygenated by the capillaries of the eyelid rather than oxygen rom the atmosphere as when the eye is open. The partial pressure o oxygen supplied from the capillaries is less than about 1/3 that supplied by the atmosphere. In the absence of a lens acting as a barrier, -the oxygen supply to the cornea, both during ~ ~`
open-eye and closed-eye periods, is sufficient.
kh o w ~ r It is-~w~r~ that a contact lens capable of continuous wear should provide at least 3.5 I~l/cm -hr, preferably 6 1ll/cm2-hr of oxygen to the corneal surface to avoid the physiological complication arising from oxygen deprivation. ~lard contact lenses r such as -those of methyl methacrylate, are not permeable g~
to oxygen, but through known lens design, permit some circulation of ~ir to the corneal surEace. Contemporary hydrogel lenses, though permeable to oxygen through the interstitial sp~ces of the hydrogel material, are not sufficiently permeable to fully oxygenate the cornea in -the cross-sections in which they are fabricated. Hence, oxygen deprivation is also encountered with these lenses.
The circulation of some oxygen using the aforesaid lenses permits daily wear of the same with minimal non-reversible damage to corneal physiology. I~owever, during closed-eye periods when the oxygen supply is reduced to less than 1/3 the level of opened-eye condition, known lens design does not permit sufficient transfer of oxygen to the corneal surface to permit wear without oxygen deprivation.
For purposes of definition herein, the term "daily wear lens" and like terms are intended to mean a lens normally worn during open-eye periods but not during closed-eye periods (i.e., during periods of sleep.) The term "continuous wear lens" and like terms are intended to mean a lens tha-t may be worn as a daily wear lens if desired but which can also be worn for extended periods of time (i.e., both during open-eye and closed-eye~ periods), if desired.
It is an object of the invention -to provide a minus prescription hydrogel contact lens tha-t can be worn on a continuous or daily basis, if desired, withou-t removal from the eye, both during opened-eye and closed-eye periods without damage to the cornea.
Another object of this invention is to provide a hydrogel minus prescrip-tion contact lens which can be removed from the eye by the patient, handled and reinserted in the eye without damage to the lens.
A further object of this invention is to provide a hydro~el minus prescription contact lens capable of continuous wear which lens permits oxygen diffusion to the cornea in sufficient quantlty to avoid the adverse effects of oxygen deprivation; avoids physiological complications arising from damaqe to the bulbar conjunctivia due to compression of the lim-bal capi:Llaries; and avoids corneal-scleral wetting deficiencies.
~ n additional object of the invention is to provide a hydrogel minus prescription contac-t lens which conforms to -the shape of the eye.
The objec-ts of the invention are accomplished with a combination of design features and hydrogel properties that .~
enable fabrication of the lens in substantially reduced cross- '~i sectional thickness and mass (weight). In this respect, -the maximum cross-sectional thickness of the lens does not exceed 0.15 mm for a daily wear lens and 0.10 mm for a continuous wear lens. Other design features of the lens include a minimum dia-meter of at least 12 mm and preferably, ranging between 13 and 17 mm; a reduced posterior peripheral curve width not to exceed 1.5 mm and preferably, total elimination of all posterior peri-pheral curves so that the base curve is a monocurve that is smooth, uninterrupted and preferably spherical; an anterior lenticular curve preferably extending from the edge of the optical zone to the periphery of the lens and havi.ng a radius such that the edge thickness of the lens does not exceed 0.08 mm and preferably, does not exceed 0.06 r~m; and physical properties such that the lens is capable of handling and conforming -to the curvature of the eye, at least in the periphery of the lens.
The hydrogel used for lens constructi.on ls one capable of containing at least 35% water of hydration and must be sufficiently rigid so as -to maintain i-ts shape in -the required thin cross section while confo~ming to the eye. A preferred class of suitable ma-terials is disclosed in United States Patent ~,9~
No. 4,056,496 supra.
With reference to the drawing, there is shown a cross section of a hydrated minus soft lens fabricated in accordance with the mos-t preferred embodimen-t of the inven-tion.
The inner surface of the lens, frequently referred to as posterior surface, comprises base curve 1 having radius 2.
In accordance with this invention, -the base curve is preferably a monocurve -- i.e., the posterior surface of the lens is smooth and of a single radius. flowever, as is known in -the art, the base curve may be provided with one or more peripheral curves (not shown in the drawing), if desired, -though this is a lesser preferred embodiment. ~lowever, if present, the peripheral curve has a maximum band width of 1.5 mm and more preferably, a maximum of 1.0 mm.
The front surface of the lens, frequently referred to as the anterior surface, comprises power or prescription curve 3 having radius 4. The width of power curve 3 is known as the optical zone of the lens (defined between points 5 and 6 of the clrawing). This width is generally sufficient to cover most, preferably all, of the cornea and hence, usually varies between about 8 and 10 mm and more typically between 8 1/2 and 9 1/2 mm.
The anterior surface of the lens also is provided with lenticular curve 7 having radius 8. The lenticular curve extends from its junction with the optical curve to the outer periphery or ed~e of the lens.
The overall diameter or chord of the lens is defined as the distance between points 9 and 10. This diameter is at least 12 mm, preferably varies between 13 and 17 mm and most preferable is about 13.5 mm.
For daily wear, the lens has a maximum cross-sectional thickncss at any point on its circumference not exceeding 0.15 mm preferably not exceeding 0.10 mm and most preferably varying 5~
..~
between about 0.05 and 0.10 mm. For con-tinuous wear,the maximum cross-sectional thickness of the lens at any point on its cir-cumference does not exceed 0.10 mm, preferably does not exceed 0.08 mm and most preferably varies between about 0.03 and 0.08 mm.
The lenses of the subject invention are thinner than those of the prior art, and the reduced thickness represents departure from the prior art. The reduced cross-section permi-ts increased oxygen diffusion through the lens thus avoiding corneal swelling tha-t would otherwise result as a consequence of oxygen deprivation on the corneal surface for an extended period of time. In this respect, it should be noted that oxygen deprivation at the corneal surface is a serious problem while depriving the conjunctivia of ~r oxygen is not a problem since it receives oxygen from the vascular system. Ilence, though a lesser preferred embodiment of the invention, the cross-sec-tional thickness of the peripheral portion of the lens, beyond the optical zone of the lens, can be thicker ~$
than the remainder of the lens without seriously compromising corneal metabolism though it is preferred to maintain the overall cross-sec-tional thickness of the lens as small as possible as this reduces the mass of the lens that rests on the surface of the eye.
The edge of the lens is also of reduced cross-section and preferably edge thickness as defined between points 11 and 12 of the drawing varies between about 0.03 and 0.08 mm and more preferably, is about 0.06 mm. A reduced edge thickness within the limits set forth is desirable as the edge will not interfere with the eyelid with normal blinking and hence drying of the scleral tissue is minimized.
The radius 2 of base curve 3 is within prior art limits and is to some extent dependent upon the shape of the eye to which the lens is fitted. The radius 4 of the power curve 3 is also within the prior art and is dependent upon the correction provided by the lens. Finally, -the radius 8 of the lenticular ~i9~i~
~ curve 7 is that necessary to provide the desired edge thickness of the lens. The lenticular curve extends from its junction with the power curve to the outermost edge of the lens and to reduce edge thickness, the curve must be steeper than the power curve. Ilence, the radius 8 of the lenticular curve 7 is shorter than radius 4 of power curve 3. Preferably, radius 8 is at least 0.2 mm shorter than radius 4 and more preferably, a-t least `
0.5 mm. It should be noted that where the lenticular curve is steeper than the power curve and particularly, in the absence of posterior peripheral curvatures, the mass of the lens is substantially reduced.
The hydroyel used to fabricate the lens is one capable of retaining its struc-tural integrity in the thin cross-sections required for the lens, is sufficiently rigid to retain a sub-stantially constant optical surface and is sufficiently flexible to permit the lens to conform to the surface contour of the eye.
The ability to conform to the surface contour of the eye is most important as it is responsible for the lens remaining firmly affixed to the eye without substantial movemen-t and change in optical surface as is frequently encountered with blinking~
Preferably, the hydrogel has a water of hydration of a-t least 35~. and preferably a water of hydration varying between 35 and 50% and more preferably between 40 and 4S%.
Preferred hydrogels are a terpolymer of a hydrophilic dihydroxy acrylate, a water-insoluble acrylate and an epoxidized acrylate.
The hydrophilic dihydroxyalkyl acrylate comonomer conforms to the general formula:
R O Oll ll l
2 C C - o - (C~12)n - CH - Cf-12~
ba~
where ~ is hydrogen or methyl and n is a whole in-teger having a value of from 0 to 4, preferably from 1 -to 4. A preferred 59L~
dihydroxyacrylate is 2,3-dihydroxypropyl methacrylate.
The second comonomer is a substantially w~ter insol-uble alkyl acrylate or methacrylate corresponding to the general formula:
R O
Cil2 = C - C ~ OR
where R is hydrogen or methyl and R' is alkyl having from 1 to 6 carbon atoms. Alkyl acrylates conforming to this formula are readily available. Examples of suitable acrylates include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl methacrylate, butyl acrylate and butyl _ ;~
methacrylate. Methyl methacrylate is most preferred.
The third comonomer is the epoxidized alkyl acrylate conforming to the formula:
R O O
, 2 C C - O - (CH2)n - CH - C~2 where R and n are as above defined. A preferred epoxidized acrylate is 2,3-epoxypropyl methacrylate.
The molar ratio of dihydroxyalkyl acrylate to alkyl acrylate varies within broad limits. Preferably, the dihydroxy-alkyl acrylate at least equals or exceeds the alkyl acrylate ancl a preferred ratio varies between about 1:1 and 10:1, more preferably between 1.2:1.0 and 2:1. The most preferred molar ratio is about 1.5:1Ø
The amount of epoxidi2ed acrylate used may vary within broad parameters, generally from 0 to 30% by weight of the dihydroxy acrylate, more preferably, from 0.1 ~o 15~ by weight and most pre~erably, from 1.0 to 7.5% dependent upon the monomers used, their ratio and -the like. A more definite amount is the amount sufficient to provide a polymer capable of absorb- r ing water of hydration in an amount of from 35 to 50%, and more preferably, from 40 to 46%.
5~
'I'he polym~rs are formed hy bulk polymerization using suitable catalysts. The monomers are mixed in the absence oE
solvent and maintained under reduced pressure at an elevated temperature for a period of time sufficient to solidify -the reaction mixture. Typically, the temperature of reac-tion varies between 20 and 60C. The catalyst concentration ma~ vary within broa~ limits dependent upon the particular catalyst used, but generally varies between about 0.001 and 0.2 weigh-t percent of the hydroxyalkylacrylate, and preferably between 0.01 and 0.0 weight percent. A preferred catalyst is isopropyl percarbonate in an amount of about 0.02 weight percent.
Other suitable lens materials would be obvious to ~Ir those skilled in the art given the property requirements set `forth herein. Thus, for example, the polymers formed by the polymerization of 2-hydroxyethyl methacrylate is described in U.S. Patent No. 3,220,960, supra, could be made suitable by an increase in the concentration of cross-linking agent so that a more highly cross-linked structure and hence, a more rigid hydrogel, would be obtained.
v-
ba~
where ~ is hydrogen or methyl and n is a whole in-teger having a value of from 0 to 4, preferably from 1 -to 4. A preferred 59L~
dihydroxyacrylate is 2,3-dihydroxypropyl methacrylate.
The second comonomer is a substantially w~ter insol-uble alkyl acrylate or methacrylate corresponding to the general formula:
R O
Cil2 = C - C ~ OR
where R is hydrogen or methyl and R' is alkyl having from 1 to 6 carbon atoms. Alkyl acrylates conforming to this formula are readily available. Examples of suitable acrylates include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl methacrylate, butyl acrylate and butyl _ ;~
methacrylate. Methyl methacrylate is most preferred.
The third comonomer is the epoxidized alkyl acrylate conforming to the formula:
R O O
, 2 C C - O - (CH2)n - CH - C~2 where R and n are as above defined. A preferred epoxidized acrylate is 2,3-epoxypropyl methacrylate.
The molar ratio of dihydroxyalkyl acrylate to alkyl acrylate varies within broad limits. Preferably, the dihydroxy-alkyl acrylate at least equals or exceeds the alkyl acrylate ancl a preferred ratio varies between about 1:1 and 10:1, more preferably between 1.2:1.0 and 2:1. The most preferred molar ratio is about 1.5:1Ø
The amount of epoxidi2ed acrylate used may vary within broad parameters, generally from 0 to 30% by weight of the dihydroxy acrylate, more preferably, from 0.1 ~o 15~ by weight and most pre~erably, from 1.0 to 7.5% dependent upon the monomers used, their ratio and -the like. A more definite amount is the amount sufficient to provide a polymer capable of absorb- r ing water of hydration in an amount of from 35 to 50%, and more preferably, from 40 to 46%.
5~
'I'he polym~rs are formed hy bulk polymerization using suitable catalysts. The monomers are mixed in the absence oE
solvent and maintained under reduced pressure at an elevated temperature for a period of time sufficient to solidify -the reaction mixture. Typically, the temperature of reac-tion varies between 20 and 60C. The catalyst concentration ma~ vary within broa~ limits dependent upon the particular catalyst used, but generally varies between about 0.001 and 0.2 weigh-t percent of the hydroxyalkylacrylate, and preferably between 0.01 and 0.0 weight percent. A preferred catalyst is isopropyl percarbonate in an amount of about 0.02 weight percent.
Other suitable lens materials would be obvious to ~Ir those skilled in the art given the property requirements set `forth herein. Thus, for example, the polymers formed by the polymerization of 2-hydroxyethyl methacrylate is described in U.S. Patent No. 3,220,960, supra, could be made suitable by an increase in the concentration of cross-linking agent so that a more highly cross-linked structure and hence, a more rigid hydrogel, would be obtained.
v-
Claims (25)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A soft minus prescription hydrogel contact lens, said lens having a maximum cross-sectional thickness at any point on its circumference not exceeding 0.15 mm having a lenticular curve extending from its junction with its power curve to the edge of the lens, the radius of said lenticular curve being at least 0.02 mm shorter than the radius of the power curve, and being of a hydrogel sufficiently rigid so as not to irreversibly deform during blinking of a wearer's eyelid and sufficiently flex-ible so as to conform to the curvature of the wearer's eye.
2. The lens of claim 1 where the maximum cross-sectional thickness does not exceed 0.10 mm at any point on its circumference.
3. The lens of claim 1 capable of continuous wear and having a maximum cross-sectional thickness that varies between about 0.03 and 0.08 mm.
4. The lens of claim 1 capable of daily wear and having a maximum cross-sectional thickness that varies between about 0.05 and 0.10 mm.
5. The lens of claim 3 having a minimum diameter of at least 12 mm.
6. The lens of claim 3 where the diameter varies between 13 and 17 mm.
7. The lens of claim 6 where the diameter is about 13.5 mm.
8. The lens of claim 3 where the posterior curve is a monocurve.
9. The lens of claim 3 where the edge thickness of the lens varies between about 0.03 and 0.08 mm.
10. The lens of claim 8 where edge thickness is about 0.06 mm.
11. A soft minus prescription hydrogel contact lens, said lens having a maximum cross-sectional thickness at any point on its circumference not exceeding 0.15 mm, a minimum diameter of 12 mm, an edge thickness ranging between 0.03 and 0.08 mm and a lenticulated curve extending from its junction with the power curve to the edge of the lens, said lenticular curve having a radius of at least 0.02 mm shorter than the radius of the power curve, said lens being of a hydrogel con-taining water of hydration in an amount of at least 35% by weight of the total weight of the hydrated lens and being sufficiently rigid so as not to irreversibly deform during blinking of a wearer's eyelid and sufficiently flexible to conform to the contour of the wearer's eye.
12. The lens of the claim 11 where the posterior curve of the lens is a monocurve.
13. The lens of claim 12 where the maximum cross-sectional thickness of the lens does not exceed 0.10 mm at any point on its circumference.
14. The lens of claim 12 capable of continuous wear and having a maximum cross-sectional thickness that varies between 0.03 and 0.08 mm.
15. The lens of claim 12 capable of daily wear and having a maximum cross-sectional thickness that varies between 0.05 and 0.10 mm.
16. The lens of claim 12 where the diameter varies between 13 and 17 mm.
17. The lens of claim 16 where the diameter is about 13.5 mm.
18. The lens of claim 12 where the edge thickness of the lens varies between about 0.03 and 0.08 mm.
19. The lens of claim 12 where the hydrogel is a hydrated terpolymer of a dihydroxyalkyl acrylate or methacry-late in major amount, an alkyl acrylate or methacrylate in minor amount and an epoxidized alkyl acrylate or methacrylate in an amount to impart the sufficient rigidity to the hydrogel.
20. The lens of claim 19 where the dihydroxyalkyl acrylate or methacrylate is glyceryl methacrylate, the alkyl acrylate or methacrylate is methyl methacrylate and the epoxid-ized alkyl acrylate or methacrylate is glycidyl methacrylate.
21. The lens of claim 19 where the hydrogel also includes a diester of an acrylic or methacrylic acid as a cross-linking agent.
22. The lens of claim 21 where the diester is a diester of glycol and methacrylic acid.
23. The lens of claim 21 where the diester is ethylene glycol dimethacrylate.
24. The lens of claim 21 where the diester is present in an amount of up to 5% by weight of all monomers.
25. The lens of claim 24 where the diester is present in an amount of from 0.1 to 4%.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/736,555 US4180308A (en) | 1972-10-02 | 1976-10-28 | Contact lens |
| US736,555 | 1976-10-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1099546A true CA1099546A (en) | 1981-04-21 |
Family
ID=24960333
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA289,638A Expired CA1099546A (en) | 1976-10-28 | 1977-10-27 | Contact lens |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5383641A (en) |
| CA (1) | CA1099546A (en) |
| DE (1) | DE2748481A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2564264A1 (en) | 2010-04-13 | 2013-03-06 | Johnson & Johnson Vision Care, Inc. | Contact lenses displaying reduced indoor glare |
| US10816822B2 (en) | 2010-04-13 | 2020-10-27 | Johnson & Johnson Vision Care, Inc. | Pupil-only photochromic contact lenses displaying desirable optics and comfort |
| US10894374B2 (en) | 2010-04-13 | 2021-01-19 | Johnson & Johnson Vision Care, Inc. | Process for manufacture of a thermochromic contact lens material |
| US11724471B2 (en) | 2019-03-28 | 2023-08-15 | Johnson & Johnson Vision Care, Inc. | Methods for the manufacture of photoabsorbing contact lenses and photoabsorbing contact lenses produced thereby |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3002664C2 (en) * | 1980-01-25 | 1989-05-18 | Titmus Eurocon Kontaktlinsen Gmbh & Co Kg, 8750 Aschaffenburg | Soft contact lens |
| AU629725B2 (en) * | 1990-01-24 | 1992-10-08 | Novartis Ag | Contact lens and process for the manufacture thereof |
| JPH06121414A (en) * | 1992-10-07 | 1994-04-28 | Fanuc Ltd | Relay module |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3220960A (en) * | 1960-12-21 | 1965-11-30 | Wichterle Otto | Cross-linked hydrophilic polymers and articles made therefrom |
| US4056496A (en) * | 1972-10-02 | 1977-11-01 | Corneal Sciences, Inc. | Hydrogels and articles made therefrom |
| US3957362A (en) * | 1972-10-02 | 1976-05-18 | Corneal Sciences, Inc. | Hydrogels and articles made therefrom |
-
1977
- 1977-10-27 CA CA289,638A patent/CA1099546A/en not_active Expired
- 1977-10-28 DE DE19772748481 patent/DE2748481A1/en not_active Ceased
- 1977-10-28 JP JP12955977A patent/JPS5383641A/en active Granted
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2564264A1 (en) | 2010-04-13 | 2013-03-06 | Johnson & Johnson Vision Care, Inc. | Contact lenses displaying reduced indoor glare |
| US9690115B2 (en) | 2010-04-13 | 2017-06-27 | Johnson & Johnson Vision Care, Inc. | Contact lenses displaying reduced indoor glare |
| US10816822B2 (en) | 2010-04-13 | 2020-10-27 | Johnson & Johnson Vision Care, Inc. | Pupil-only photochromic contact lenses displaying desirable optics and comfort |
| US10894374B2 (en) | 2010-04-13 | 2021-01-19 | Johnson & Johnson Vision Care, Inc. | Process for manufacture of a thermochromic contact lens material |
| US11391965B2 (en) | 2010-04-13 | 2022-07-19 | Johnson & Johnson Vision Care, Inc. | Pupil-only photochromic contact lenses displaying desirable optics and comfort |
| US11724472B2 (en) | 2010-04-13 | 2023-08-15 | Johnson & Johnson Vision Care, Inc. | Process for manufacture of a thermochromic contact lens material |
| US11789291B2 (en) | 2010-04-13 | 2023-10-17 | Johnson & Johnson Vision Care, Inc. | Pupil-only photochromic contact lenses displaying desirable optics and comfort |
| US11724471B2 (en) | 2019-03-28 | 2023-08-15 | Johnson & Johnson Vision Care, Inc. | Methods for the manufacture of photoabsorbing contact lenses and photoabsorbing contact lenses produced thereby |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5383641A (en) | 1978-07-24 |
| JPS6227362B2 (en) | 1987-06-15 |
| DE2748481A1 (en) | 1978-05-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |