CA1197717A - Extraocular contact lens construction - Google Patents
Extraocular contact lens constructionInfo
- Publication number
- CA1197717A CA1197717A CA000438358A CA438358A CA1197717A CA 1197717 A CA1197717 A CA 1197717A CA 000438358 A CA000438358 A CA 000438358A CA 438358 A CA438358 A CA 438358A CA 1197717 A CA1197717 A CA 1197717A
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- lens
- haptic
- rabbet
- glass
- lens assembly
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Abstract
ABSTRACT OF THE DISCLOSURE
The invention contemplates improved extraocular-lens structures for contact with the cornea of a human eye, to be worn in place of spectacles. The construction features a lens element of requisite prescription power but of diameter which substantially equals or only slightly exceeds the fully dilated pupil side of the wearer, and fenostrated haptic structure peripherally engaged to the lens. The haptic structure extends radially outwardly and is so thin and axially compliant as to be self-conforming to the curvature of the cornea and to effectively adhere thereto, thus stabilizing the lens for retention of its position on the optical axis of the eye. The haptic structure is formed by two sheets of transparent material laminated to opposite sides of the lens and to each other. The effective surface of the haptic area is reduced by photographically delineated milling to fenestrate the haptic structure radially outwards of the lens.
The invention contemplates improved extraocular-lens structures for contact with the cornea of a human eye, to be worn in place of spectacles. The construction features a lens element of requisite prescription power but of diameter which substantially equals or only slightly exceeds the fully dilated pupil side of the wearer, and fenostrated haptic structure peripherally engaged to the lens. The haptic structure extends radially outwardly and is so thin and axially compliant as to be self-conforming to the curvature of the cornea and to effectively adhere thereto, thus stabilizing the lens for retention of its position on the optical axis of the eye. The haptic structure is formed by two sheets of transparent material laminated to opposite sides of the lens and to each other. The effective surface of the haptic area is reduced by photographically delineated milling to fenestrate the haptic structure radially outwards of the lens.
Description
7~l~
~ lis invention relates particularly to extraocular~lens structures for contact application to the cornea, for wear in place of spectacles.
Conventional contact lenses, be they of the hard or soft variety, are circular, of 12 to 14mm diameterJ and thus cover a relatively large area, approximating the area defined by the perimeter of the iris. They are larger than optically necessary because the only light rays they need accommodate are those permitted by ~he pupil, and their relatively large area is a source of discomfort because fluid on the cornea is thereby precluded natural flow and circulation; as a consequence, the wearer of contact lenses must accustom himself to relatively frequent removal, cleaning and replacement of his lenses. But if the conventional contact lens were any smaller, it would be virtually incapable of manipulation by the wearer, and it would also be prone to move off-axis, over the corneal surface. Furthermore, liquid and gas-permeable plastics have recently been used, but lenses of such materials tend to build enzyme deposits and present difficulties in regard to cleaning and sterilization.
As far as I am aware, glass has been foreclosed as a contact-lens material, due to its high density and fragility, compared to that of plastic materials. And the manufacture of contact lenses has involved plastic-molding techniques where prescription curvatures are derived from a moldingcavity, or by lathe-cutting, i.e., they are not expressly ground into the lens itsel~. And being circular, there is no way that astigmatism can be corrected through con~entional contact lenses because there is no way of identifying orientation parameters of the astigmatism.
Brief Statement of the Invention It is an object to provide an improved extraocular or contact-lens ` construction.
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It is a specific object to provicle such a construction wherein the lens element itself may be of substantially smaller size, consistent essentially only ~ith its optical requirements, and wherein haptic structure engaged to the lens element provides stabilized positioning for the lens element.
The invention provides a contact-lens assembly adapted for removable mounting to the cornea of an eye, comprising an optically finished lens element having a circular periphery characterized by a peripherally continuous rabbet formation at one axial side of said element, and a single-piece haptic of flexible sheet material having a circular opening at the rim of which said haptic has circumferentially continuous seated engagement with said rabbet formation and thereby mounts said lens element.
The invention also provides a contact-lens assembly adapted for removable mounting to the cornea of an eye, comprising meniscus-lens means of optical glass having a circular periphery characterized by a peripherally continuous rabbet formation at one axial side of said lens means, and single-piece annular haptic means of sheet material having a circular opening at the rim of which said haptic means has circumferentially continuous seated engagement with said rabbet formation and thereby mounts said lens means, said haptic means having generally spherically dished convex and concave surfaces at its respective axial ends, ~he convex surfaces of said haptic means and of said lens means being at the same axial end of said assernbly.
The invention further provides a glass contact-lens element having a circular periphery characterized by a circumferentially continuous rabbet formation at one axial end, said rabbet formation being adapted to mount to the central aperture of suitable haptic structure, said glass element being characterized by spaced longitudinally open passages of combined effec~ive ~7~i7 sectional area which is less than one per cent of the peripherally included area of said lens element.
~rom another aspect, this invention provides the method of making . a two-piece contact-lens assembly, wherein a circular lens element having a - peripherally continuous rabbet wlth land and shoulder surfaces at one axial side is engaged at the rabbet to the circular rim of a centrally apertured flexible haptic element of heat-expandable sheet material, which method comprises heating said haptic element to expand the rim circumference of its circular aperture, such expansion being to a degree to permit axial i.nsertion of the rabbet land sur:Eace to be engaged, making such insertion to the point of axial location at the shoulder surface of the rabbet formation, and retaining the thus-assembled relation while allowing the haptic element to cool and thus shrink into said tensed engagement.
The invention also provides the method of making a glass contact-lens element of meniscus configuration and adapted for assembly to a mounting haptic, which method comprises selecting a thin sheet of optical glass of desired refractive index, chemically etching a circular line to define and separate a lens blank from said sheet, selecting a pair of die elements having cooperating convex and concave surface curvatures appropriate to desired ultimate meniscus-lens curvatures, heating the lens blank to softened condition, forming meniscus curvatures by axially compressing the softened blank between sa.id die elements, and allowing the die-formed blank to cool.
The invention also provides the method of making a two-piece glass contact-lens assembly wherein a glass contact-lens element of meniscus con-figuration is assembled to a dished glass haptic element, which method comprises selecting a thin sheet of optical glass of desired refractive index, ~ 3 --- \
chemically etching a circular line to dcfine and separate a lens blank from said sheet, selecting a thin sheet of glass and etching the same to define a blank for the haptic element, assembling both blanks to ultimate co-axial relatioll, selecting die elements havlng cooperating convex and concave surface curvatures appropriate to desired ultimate meniscus-lens curvatures and to desired ultimate dished haptic curvature, heating the assembled blanks to softened conditionJ concurren~ly forming the meniscus curvatures and the haptic curvature by axially compressing the softened blanks between said die elements, and allowing the die-formed assembled blanks to cool.
The invention also provides the method of making a glass con~act-lens element having a circular periphery characterized by a rabbet formation at one axial end, which comprises selecting a thin sheet of optical glass of desired refractive index, cutting a circular blank from said sheet by chemically etching a circular border line to characterize the blank with said circular periphery, chemically etching said rabbet formation from said one axial end, chemically etching in said blank a plurality of spaced longitudinally open passages of combined effective sectional area which is less than one per cent of the peripherally included area of said lens element, heating said blank to sof~en the same, and compressionally forming front and back lens surfaces on the softened blank.
The haptic means is readily self-adapting to the curvature of the cornea, and permits the employment of optical glass as the material of the lens element. The contact-lens construction i5 also capable of supplying astigmatism correction for the ~earer, and can be cleaned and sterilized by boiling in water or by autoclaving.
; Glass may be safely used as the optical element and *he structure is relatively simple and lends itself to quantity and precision manufacture, 77~L'7 provides lmproved comfort to the wearer, and involves substantially reduced demands for removal, cleaning and replacement.
The lens element is of substantially reduced diameter (e.g.> 5 to 8mm), and is thus essentially only of the size required to serve a fully dilated pupil, and the fenestrated compliant haptic structure engages the lcns element and adheres to the wet sur:Eace of the cornea for stabili~ed support of the lens element. The resul-t is a much lighter-weight article, of less bulk than conventional contact lenses, and permi~ting the use o~ optical glass for the lens element.
The invention will be illustratively described in conjunction wi-th the accompanying drawings, in which:
Figure 1 is a simplified fron*-elevation view of a human eye to which contact-lens structure of the invention has been applied;
Figure 2 is an enlarged view of the lens structure of Figure 1 to show haptic detail;
Figure 3 is a side-elevation view of the structure of Figure 2;
Figure 4 is a view similar to Figure 3 but wlth the separate parts in exploded relation;
Figure 5 is a view similar to Figure ~ to show a modification;
Figure 6 is a sectional view, taken at 6-6 of Figure 2 and on a further-enlarged scale;
Figure 7 is a view similar to Figure 2, to show a modification;
Figures 8 and 8A are fragmentary views, otherwise similar to Figures 7 and 2, respectively, to show another modification;
Figures 9 and 9A are similar to Plgures 8 and 8A, to show further modification;
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~77~7 Figures 10 and IOA are views similar to Figures 3 and 4 respectively, to show further modification;
Figures 11 and 12 are views similar to Figur~s 5 and 3, respectively~
*o show further modiication;
Figures 13, 14 and 15 are similar end views to show illustratively varied formations in the lens element of Figures 11 and 12; and Figure 16 is a simplified view in elevation~ partly broken away and in longitudinal section, to show a compression-die configuration to produce contact-lens structure of Figure 12.
In the form of Figures 1 to 4, the invention is shown in application to an extraocular or contact-lens assembly comprising a central lens element 10 which may be of molded plastic, but which is preferably of optically finished glass, ground to prescription curvature le.g., plano-convex or meniscus) and of outside diameter Dl which equals or sligh~ly exceeds the diameter of the fully dilated pupil o~ a human eye. As is clear from Figure l, the diameter Dl is very much less than the diame~er D2 of the iris 12 of the eye ll. Generally speaking, the diameter Dl, is in the range 5 to 8mm, and the diameter D2 is in the range of 12 to 14mm~ the latter being the diameter of a conventional contact lens.
Fixed to and centrally supporting the lens element 10 is a haptic 13 of much larger included area than the lens element 10. Haptic 13 comprises two thin sheets 14-15 of plastic material laminated to the front and back surfaces of lens element 10, and to each other in regions radially ou~side element 10; in these outer regions, haptic 13 is characterized by very substantial fenestration, meaning that the structure is primarily "open", for normal air or "breathing" exposure of the surface o:~ the cornea. Such ~9~'7~7 fenestration may be by photographically delineated milling, before or after lamination of the sheets 14-15 to each other, relying upon such chemical-etching, plasma and other milling techniques as are described for intraocular lens haptics, in my United States Letters Patent 4,0~0,70g.
More specifically, each of the sheets of haptic 13 is seen to be o~ generally oval or elliptical outer contour and to comprise four radially outward foot formations, there being a first larger pair 16-17 on the major axis and a second shorter pair 18-19 on ~he minor axis. It is intended that these ~oot formations be very compliant in the axial direction, to render them self-conforming to the surface of the cornea. Each foot formation, taking formation16 as ~ypical, comprises angularly spaced outer legs 20 and a central leg 21 integrally connecting an inner hub portion 22 to an outer bridge portion 23;
and intermedia~e their points of interconnection all these elemental areas are slotted, as at 2~, to render them 0ven more self-confirming to the surface of the cornea. The sheets 14-15 should be selected for auto-clavability and may be of l-mil or 0.5 mil material, suitably nylon, high-density polyethylene, Mylar*, Teflon*, polyethersulfone, polyester, sheet silicone, or H.E.M.A., meaning that in the elemen~al areas 20-21-22-23, the haptic is o~ thickness T
(Figure 6) in the range of 1 to 2 mils; the width Wl of each of these areas is typically in the order of 10 mils, and slot widths W2 are in the order of 3 mils. The overall dimensions of the haptic blank may suitably be 16mm.
(major axis) by 12mm ~minor axis). Bonding o~ the plastic sheets 1~-15 to each other may be by suitable ultrasonic, heating or cemen~ing techniques, as applicable.
Prior to application to the cornea, the foot formations 16-17-18-19 are so a~ially weak ("floppy") as to be apparently useless as supports for * Trade Marks of the DuPont Company ~33'7'~7 the associated lens element 1~. However, once the central lens-bearing region is placed over the pupil~ ~he adjacent floppy hap~ic regions are drawn, by a self-wetting action akin to surface tension and/or capillary attraction (in the context of surface moisture on the cornea) to lie down on the cornea in con:Eormance to locally adjacent curvature of the cornea. In addition to rendering the elemental areas 20-21-22-23 more compliant, tlle slotted regions ~24) thereof achieve a pump-like coaction wi~h surface liquid on the cornea, with the result that surface liquid is locally displaced and drawn into and through the slotted regions (24), and essentially all haptic area radially outside the lens element 10 has an affinity :for the cornea region to which it has "attached" itself by self-wetting. Thus, the relatively narrow and slotted nature of areas 20-21-22-23 promotes displacemen~ of surface liquid, with the attendant benefit of cleaning and lubricating action, particularly when blinking the eyelid over the installed structure. And the 1 to 2-mil haptic thickness encountered by a blinking eyelid is inconsequential, while the lens elemen~ remains sufficiently anchored in its installed eye-axis position, it being further noted that, as a result of using the indicated milling techniques, all edges of the haptic formations are smoothly rounded and therefore not a source of irritation The anchoring effect is enhanced by providing a mildly roughened surface (as by etchin~) on the posterior side of the haptic areas 20-21-22-23, and the smoothness of eyelid action is enhanced by providing a smooth anterior surface of the haptic; the roughened surface will have been created prior to milling and will have a ~lull or matte appearance, and the smooth surface will be shiny, thus enabling ready identification of the front and back surfaces of the assembly.
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In the form of Figures 1 to ~, the sheets 14-15 continuously ~nd intimately cover the respective front and back surfaces Oe lens element 10.
The selected plastic material of sheets 14-15 must therefore be for their transparenc~, and as noted previously, reliance is upon the lens element 10 for optical properties. Generall~, it may be observed that use of plastic material for lens element 10 means an index of refraction substantially less than that of glass. rherefore, production of plastic lens elements 10 will mean greater curvature (shorter radii), and therefore greater lens thickness, than for a glass lens element 10 of the same diopter specification. In the case of the glass lens element 10, optical glasses are commercially available with various indices of refraction in the range 1.4 to 2.0, and I find that by grinding all lens elements 10 ~as optically finished plano-convex elements), with the same single radius of curvature (e.g., 300-mm radius), a full range of prescribable diopter powers (at quarter-diopter increments, up to 10 diopters) is available merely by choice of the glass for its particular index of refraction; a similar single-radius approach in grinding negative-lens surfaces will also serve a wide range of diopter prescriptions, *hrough appropriate selection of a particular glass for its index o refraction.
Further, because glass elements 10 may be finished with prescribable grinding eccentricity, astigmatism correction can be provided, the lens element being oriented with its astigmatic-correction axis rotationally displaced to a prescribed angular orientation with respect to~ say, the major axis 16-17 upon assembly to and lamir,ation with the haptic parts 1~-15; the exposed dull vs. shiny surfaces of the haptic, being recogniæably exposed, enable the user to make sure that his installed lens (major axis horizontal, shiny side facing forward) will always be so installed in his eye as to avoid astigmatic ambiguity.
_ 9 Figure 5 illustrates a modification ~herein each of the haptic sheets 14'-15' is formed with a central aperture of diameter D3, to enable peripheral overlap with the rim of lens element 10; lamination of the sheets 14'-15' and their substantial ~enestration radially outside lens element 10 is otherwise as described for Figures 1 to 4. m e diameter D3 is illustratively 4.5 to 5~n, to allow such peripheral o~erlap to the radial extent of O.S to 0.75mm, for the case of a 6-mm diameter Dl of lens element 10.
Figure 7 depicts an alternative construction, partlcularly suited to eyes for which no astigma~ism is to be corrected. The only significant difference in Figure 7 is that the outer perimeter of the haptic 30 thereof is generally circular. In other words, all foot formations 31-32-33-34 are alike, and preferably comprise slotted elemental hub, foot, and bridge areas corresponding to areas 20-21-22-23 of Figure 2.
Figures 8 and 8A respectively illus~rate circular and elliptically con~oured embodiments of a modified version of the in~ention, particularly suited to the a-tonic iris, i.e., an eye having no iris or a damaged iris.
One or both of the sheets which comprise the haptic 40 (40') is characterized by an opaque a~mular region 41 (41') extending from the lens-lapping inner diameter D3 to an outer diameter D4 to match ~he person's other-eye iris diameter. Foot formations 43-44 (43'-44') extend radially outward of the hub region of lens element retention, but the major open fenestration is radially outside the annulus 41 (41'~, the "opaque" region 41 ~41') being desirably foraminated with apertures of diameter preferably less than substantially 0.005 inch and at least as great as the thickness of region 41 (41'), to permit "breathing" action of the corneal surface covered thereby.
Desirably, the "opaque" region is so finished as to color and design as to '7~7~
create the appearance of a normal iris in the afflicted eye.
~ igures 9 and 9A illustrate modification o~` the respective circular and elliptical embodlments o~ Figures 7 and 2~ wherein the haptic 50 (50') is peripherally continuously a circle or an ellipse or oval. Slotting of elemental areas of haptics 50 (50') is again preferred, as described for Figure 2.
The 10ppy nature of the continuous periphery of both haptics SQ (50') enables continuous intimate attraction to the cornea surface in the manner described for Figures 1 to ~, and the plurality o~ axially compliant radial leg elements 51 (52-53) is preferably at least three~ being shown as four, for both Figures 9 and 9A.
Figures 10 and lOA are directed to an all-glass embodiment oE the invention wherein the lens element 10 is an optically finished element, shown as plano-convex and with a cylindrical rim of thickness T2 in the range 1 to 3 milsJ preferably substantially 2 mils. The flat posterior side of lens element 10 is mo~mted, as by fusing or ~y a suitable cementJ to the central region of a sheet ~lass haptic 60 o~ thickness in the range 0.5 to 1.5 mils, preferably 1 mil. Fenestration is provided in the haptic region external to lens element 10, in the manner discussed above for the forms of Figures 2 and 7, 9 and 9A, as the case may be. The glass haptic 60 is thus substantially as floppy as its plastic counterpart, but it has the advantage of being less susceptible to bacteria-growth phenomena, and therefore less likely or less ; oEten to require removal for cleaning and sterilization; its ultimately flexed curvature in adaptation to the cornea is suggested by dashed lines 60.
~ Figures 11 and 12 illustrate a ~urther embodiment wherein the ; element 10' is a meniscus--lens, having a concave axial-end surface oE first spherical radius Rl and a convex ou~er or opposite-end surface of second spherical radius R2; in the illustration Rl is shown to exceed ~2 and thus to de~ine a positive meniscus~lens 10', bu-t the relation of Rl to R2 will be understood to be dictated by prescription appropr:iate to the op~ical correction needed by a particular eye. The circular periphery of lens element 10' is characterized by a rabbet formation 65, which may be etched, thus establishing a substantially cylindrical land of diameter D5; the land terminates at a radially outward shoulder of outer diameter D6, being the peripheral limit of the lens element. Typically, D6 will be in the range 6.5 to lOmm, and the etched shoulder height ~ R of the rabbet will be 0.1 to 0.25 mm, so that D5 may be 6mm or larger; at the same time, the axial depth T3 of the rabbet may be about 0.05mm, thus constituting a rela~ively harmless incursion upon the rim thickness T4 of the lens element, T~ being abou~ O.lmm, and the ~iml thickness T~ ~see Figure 12) being approximately 0.5mm and of course dependen~ on particular curvature radii Rl and R2. The curvature radii will generally be about 300mm, respectively differing as much as 9mm from each other, it being understood that the sense of the difference determines whether the lens elemen~ 10' is positive or negative.
The haptic 66 to which lens element 10' is assembled is shown flat in Figure 11, since it is an annular blank cut, preferably by etching, from thin sheet material which may ~e glass or a suitable plastic. The cent:ral opening 67 of haptic 66 may be of the diameter D5 of the rabbet land to which it is fitted; whether of glass or plastic, a suitable cemen~ inert to bod~
fluids may be employed to secure the assembled haptic (66) and lens (10') elements. Preferably, however, if haptic 66 is of glass, the diameter of opening 67 is selected for such slight interference with the diameter of the rabbet land that (1) upon heating to expand opening 67J the haptic will ~ 9 ~ t~
insertably receive the rabbet land to the point of circumferential abutment with the rabbet shoulder and (2) upon allowing the thus-assembled parts to cool, a sligh~ residual circumferential tension (clamping) will develop in haptic 66 to permanently retain the assembled relationship.
The preferred material for lens element 10' is optical glass, of selected index o refraction as previously noted. And in that event, the rabbet 65 is preferably the result of suitably masked chemical etching, the etching proceeding axially from one to the exclusion of the other axial end of the lens element; as shown, the rabbet and the rabbet-forming etch involve only the convex end of the lens element. A suitable etchant is hydrofluoric acid, diluted to about 20 per cent in water.
It is a feature of the invention that the lens element 10', although much smaller than those in curren~ contact-lens use, shall be characterized by spaced through-passages, such as passages 68 in Figure 13~ for permitting air access to a corresponding plurality of lens-covered regions of the cornea.
~s shown, in Figure 13, three such passages are provided~ at equal spacing from each other and on a single common geometrical circle of diameter D7 about ` the central optical axis. In Figure l~ such passages are shown equally spaced on each of two concentric circles of diameters D8-D8' about the axis, and is Figure 15, the Dg diameter circle of such passages surrounds a central passage 68' of the same character.
The passages 68-68' of Figures 13 to 15 may suitably be of 0.25 to 0.5mm diameter and the geometrical circle diameters may be in the range of to 8mm, depending on the number and distribution of the passages and the peripheral diameter D6 of the lens element. In any case, however, the combined sectional area of all such passages is preferably less than one per ~ 1 ~'7~7~.'7 cent of the peripherally included area of the lens, so that "breathing" is possible without degrading vision.
~ hile it is possible and highly satisfactory to provide ground optically finished front and back surfaces for a glass lens element 10', this is a relatively expensive technique. My current preference is to use compression dies on a heat-softened blank to form the desired convex and concave surfaces of the lens. Such apparatus is shown, simplifiedJ in Pigure 16. Basically, an annular body 70 pro~ides a straight cylindrical bore 71 of diameter to clear and locate an inserted blank for element 10'. Bore 71 receives a bottom-inserted fixed-die element 72 having an upper convex spherical surface of radius Rl on a central axis 73; at its other end~ bore 71 provides axial guidance for a movable-die element 74 having a lower concave spherical surface of radius R2, also on the central axis. Assuming the prior etching of rabbet 65, a heat-softened flak glass blank for element 10' is inserted in bore 71 (rabbeted side up) so that upon descent of the upper die element 74, the projected rim 75 at the periphery of the concave end of element 74 will locate in the rabbet 65 upon inikial contact with element 10'.
Ihereafter~ compression of die elements 7~-72 squeezes the softened glass blank into its ultimate desired curvatures, dependent of course upon the curvatures associated with the respective convex and concave forming surfaces of the die elements.
What has been described thus far applies to the manufacture of lens elements 10' in which no astigmatic correction is prescribed, namely, meniscus-lens elements in which Rl and R2 are centered on the optical axis of the element 10'. To provide for astigmatic correckion, it is merely necessary that for one of the die elements 72 or 74, the curvakure-forming spherical 77~7 surface thereof shall be based on a center that is offset from the optical axis (i.e.~ ecc0ntric with respect to tlle center o~ the other die-element spherical surface), the extent of the offset being of course a function of the prescrip~ion s~a~ement of degree of correction required. In the event of such eccentric offset, it is convenient to e~ternally indicate the angular direction of the offset, as by appropriate edge marking on the flange 72' (or 7~') of the die element 72 ~or 74~ having the eccentric offset of its spherical center.
The haptic 66 is also preferably etch-cut ~rom thin fla~ sheet glass stock, and is therefore initially as shown in Figure ll. According to one method of assembly, such a glass haptic blank is heat-softened and compression-die formed into dished spherical shape in conformance with cornea curvature, prior to its assembly to the inserted element 10'; such forming is exemplified in Figure 12, being shown after completion of its above-described assembly. It will be understood that the chemical etching by means of which the haptic bla~k is cut from sheet stock may also provide fenestration as desired in the haptic blank. Such fenestration may take one of the forms described in connection with Figures 1 to 9, or it may be o~herwise as desired, for example, foraminated with spaced apertures as described at 68 for lens element lO'.
It is also desirable that either the etched design or the die-forming design operative upon the haptic 66 shall provide a built-in recognizable angular reference identification (indicium) so that the ultimate user can always apply his lens assembly in consistently correct angular orientation; such a die-formed indicium appears at 79 in Figure 12. Recognizable ori~ntation is particu-larly important when the lens element lO' incorporates astigmatism correction, and it will be understood that the angle identification mentioned above in connection with eccentric offset in the die-elemen~ relation mus~ be correctly 7~
positioned with respect to the haptic reference identi.fication (indicium), upon haptic to lens element assembly, the correct angular -rela~ion being as prescribed for the ultimate user's eye.
The described embodiments of the invention will be seen to achieve all stated objects. Importantly, the invention brings light weight and substantially reduced bul~ and surface area to the contact-lens art7 plus the inherent capability of providing optically finished glass lens elements, with astigmatic correction, i needed; further, photochromic glass at lO
provides a hitherto ~mavailable feature in a contact lens configuration.
Fenestration areas are substantial, radially outside the supported lens element 10, being preferably at least four times the end area of the lens element, such area being taken as within effective perimeter limits of the geometric circular or oval ~elliptical) contour to which the foot formations are tangent. Except for the "opaque" annulus ~ ) of Figures 8 and 8A, all other haptic regions and materials are preferabLy clear and transparen~, foot formations of such haptic regions being effectively i.nvisible to the eye of an observer.
Not only does the invention bring above-noted benefits of optically finished glass to the contact-lens art, but an i~portant safety factor is also provided. In embodiments involving plastic-shee~ haptics, the plastic sheets of the haptic fully enclose and support the lens element in at least the region of its rim; in other words, it is at least the most delicate and racturable part of the lens ~hich is protected by such plastic-sheet enclosure.
In glass haptic situations as described in connection with Figures 10 and lOA, the haptic sheet 60, being bonded to lens element 10 over its full area, provides reinforcement to the otherwise more fracturable rim region of the ~ 16 -~ ~'77~7 lens element 10; in the event that lens element 10 is a meniscus-lens, the haptic sheet 60 is preferably centrally open to the diameter D3 (see Figure S), but there will be an annular overlap (Dl, minus D3) within which sheet 69 and lens 10 are bonded, thus providing lens-rim reinforcement, in addition to the described support and positioning flmctions of the haptic. And in the etched-glass situations discussed in connection with Pigures 11 to 15, it wi]l be noted that as a result of chemical etching there is no chipping, nicking or the like degradation of remaining glass, as at the rabbeted periphery, so that inherent strength and resistance to shatter are preserved in the etched glass components.
It should be further observed that although curvatures and diopter ranges have been mentioned by way of illustration, these ranges are in no sense by way of limiting the invention. For example, the invention will be seen to have application to aphakic patients3 i.e., to those whose cataracted natural lens has been surgically removed but for whom an external lens, rather than an implanted intraocular lens, has been prescribed. Such lenses may be of the structure, nature and combinations herein described, but with a stronger finished optical element 10, e.g., having power in the order of 10 or more diopters. When such stronger lenses are of glass, the thickness of the lens i 20 element 10 per se will still be very much less than for a conventional contact-lens prescribed for the same situation.
While the invention has been described in detail for preferred forms shown, it will be understood that modifications may be made without departure from the claimed scope of the invention. For example, the technique of retaining an optical element by and between laminated plastic sheets whi.ch become the haptic lends itself to intraocular-lens application, so that for ~'77~'~
example, a configuration as in Pigure 7, and with three or more foot formations within an outer circular locus of 12 to l~mm diameter may serve well for anterior-chamber implan~ation, relying upon the foot formations to develop stabilizing support at the scleral ridge (adjacent the base of the iris). Of course, in that event, the haptic sheets should provide a more stiff radial-support action, in that they stand without contact analogous -to the described cornea-adherent extraocular applications herein; thus, for intraocular application the overall haptic thickness Tl is preferably about lO mils, and of course lens curvatureswill be of shorter radius in view of the vitreous-humor environment in which such lenses must function.
~ lis invention relates particularly to extraocular~lens structures for contact application to the cornea, for wear in place of spectacles.
Conventional contact lenses, be they of the hard or soft variety, are circular, of 12 to 14mm diameterJ and thus cover a relatively large area, approximating the area defined by the perimeter of the iris. They are larger than optically necessary because the only light rays they need accommodate are those permitted by ~he pupil, and their relatively large area is a source of discomfort because fluid on the cornea is thereby precluded natural flow and circulation; as a consequence, the wearer of contact lenses must accustom himself to relatively frequent removal, cleaning and replacement of his lenses. But if the conventional contact lens were any smaller, it would be virtually incapable of manipulation by the wearer, and it would also be prone to move off-axis, over the corneal surface. Furthermore, liquid and gas-permeable plastics have recently been used, but lenses of such materials tend to build enzyme deposits and present difficulties in regard to cleaning and sterilization.
As far as I am aware, glass has been foreclosed as a contact-lens material, due to its high density and fragility, compared to that of plastic materials. And the manufacture of contact lenses has involved plastic-molding techniques where prescription curvatures are derived from a moldingcavity, or by lathe-cutting, i.e., they are not expressly ground into the lens itsel~. And being circular, there is no way that astigmatism can be corrected through con~entional contact lenses because there is no way of identifying orientation parameters of the astigmatism.
Brief Statement of the Invention It is an object to provide an improved extraocular or contact-lens ` construction.
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It is a specific object to provicle such a construction wherein the lens element itself may be of substantially smaller size, consistent essentially only ~ith its optical requirements, and wherein haptic structure engaged to the lens element provides stabilized positioning for the lens element.
The invention provides a contact-lens assembly adapted for removable mounting to the cornea of an eye, comprising an optically finished lens element having a circular periphery characterized by a peripherally continuous rabbet formation at one axial side of said element, and a single-piece haptic of flexible sheet material having a circular opening at the rim of which said haptic has circumferentially continuous seated engagement with said rabbet formation and thereby mounts said lens element.
The invention also provides a contact-lens assembly adapted for removable mounting to the cornea of an eye, comprising meniscus-lens means of optical glass having a circular periphery characterized by a peripherally continuous rabbet formation at one axial side of said lens means, and single-piece annular haptic means of sheet material having a circular opening at the rim of which said haptic means has circumferentially continuous seated engagement with said rabbet formation and thereby mounts said lens means, said haptic means having generally spherically dished convex and concave surfaces at its respective axial ends, ~he convex surfaces of said haptic means and of said lens means being at the same axial end of said assernbly.
The invention further provides a glass contact-lens element having a circular periphery characterized by a circumferentially continuous rabbet formation at one axial end, said rabbet formation being adapted to mount to the central aperture of suitable haptic structure, said glass element being characterized by spaced longitudinally open passages of combined effec~ive ~7~i7 sectional area which is less than one per cent of the peripherally included area of said lens element.
~rom another aspect, this invention provides the method of making . a two-piece contact-lens assembly, wherein a circular lens element having a - peripherally continuous rabbet wlth land and shoulder surfaces at one axial side is engaged at the rabbet to the circular rim of a centrally apertured flexible haptic element of heat-expandable sheet material, which method comprises heating said haptic element to expand the rim circumference of its circular aperture, such expansion being to a degree to permit axial i.nsertion of the rabbet land sur:Eace to be engaged, making such insertion to the point of axial location at the shoulder surface of the rabbet formation, and retaining the thus-assembled relation while allowing the haptic element to cool and thus shrink into said tensed engagement.
The invention also provides the method of making a glass contact-lens element of meniscus configuration and adapted for assembly to a mounting haptic, which method comprises selecting a thin sheet of optical glass of desired refractive index, chemically etching a circular line to define and separate a lens blank from said sheet, selecting a pair of die elements having cooperating convex and concave surface curvatures appropriate to desired ultimate meniscus-lens curvatures, heating the lens blank to softened condition, forming meniscus curvatures by axially compressing the softened blank between sa.id die elements, and allowing the die-formed blank to cool.
The invention also provides the method of making a two-piece glass contact-lens assembly wherein a glass contact-lens element of meniscus con-figuration is assembled to a dished glass haptic element, which method comprises selecting a thin sheet of optical glass of desired refractive index, ~ 3 --- \
chemically etching a circular line to dcfine and separate a lens blank from said sheet, selecting a thin sheet of glass and etching the same to define a blank for the haptic element, assembling both blanks to ultimate co-axial relatioll, selecting die elements havlng cooperating convex and concave surface curvatures appropriate to desired ultimate meniscus-lens curvatures and to desired ultimate dished haptic curvature, heating the assembled blanks to softened conditionJ concurren~ly forming the meniscus curvatures and the haptic curvature by axially compressing the softened blanks between said die elements, and allowing the die-formed assembled blanks to cool.
The invention also provides the method of making a glass con~act-lens element having a circular periphery characterized by a rabbet formation at one axial end, which comprises selecting a thin sheet of optical glass of desired refractive index, cutting a circular blank from said sheet by chemically etching a circular border line to characterize the blank with said circular periphery, chemically etching said rabbet formation from said one axial end, chemically etching in said blank a plurality of spaced longitudinally open passages of combined effective sectional area which is less than one per cent of the peripherally included area of said lens element, heating said blank to sof~en the same, and compressionally forming front and back lens surfaces on the softened blank.
The haptic means is readily self-adapting to the curvature of the cornea, and permits the employment of optical glass as the material of the lens element. The contact-lens construction i5 also capable of supplying astigmatism correction for the ~earer, and can be cleaned and sterilized by boiling in water or by autoclaving.
; Glass may be safely used as the optical element and *he structure is relatively simple and lends itself to quantity and precision manufacture, 77~L'7 provides lmproved comfort to the wearer, and involves substantially reduced demands for removal, cleaning and replacement.
The lens element is of substantially reduced diameter (e.g.> 5 to 8mm), and is thus essentially only of the size required to serve a fully dilated pupil, and the fenestrated compliant haptic structure engages the lcns element and adheres to the wet sur:Eace of the cornea for stabili~ed support of the lens element. The resul-t is a much lighter-weight article, of less bulk than conventional contact lenses, and permi~ting the use o~ optical glass for the lens element.
The invention will be illustratively described in conjunction wi-th the accompanying drawings, in which:
Figure 1 is a simplified fron*-elevation view of a human eye to which contact-lens structure of the invention has been applied;
Figure 2 is an enlarged view of the lens structure of Figure 1 to show haptic detail;
Figure 3 is a side-elevation view of the structure of Figure 2;
Figure 4 is a view similar to Figure 3 but wlth the separate parts in exploded relation;
Figure 5 is a view similar to Figure ~ to show a modification;
Figure 6 is a sectional view, taken at 6-6 of Figure 2 and on a further-enlarged scale;
Figure 7 is a view similar to Figure 2, to show a modification;
Figures 8 and 8A are fragmentary views, otherwise similar to Figures 7 and 2, respectively, to show another modification;
Figures 9 and 9A are similar to Plgures 8 and 8A, to show further modification;
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~77~7 Figures 10 and IOA are views similar to Figures 3 and 4 respectively, to show further modification;
Figures 11 and 12 are views similar to Figur~s 5 and 3, respectively~
*o show further modiication;
Figures 13, 14 and 15 are similar end views to show illustratively varied formations in the lens element of Figures 11 and 12; and Figure 16 is a simplified view in elevation~ partly broken away and in longitudinal section, to show a compression-die configuration to produce contact-lens structure of Figure 12.
In the form of Figures 1 to 4, the invention is shown in application to an extraocular or contact-lens assembly comprising a central lens element 10 which may be of molded plastic, but which is preferably of optically finished glass, ground to prescription curvature le.g., plano-convex or meniscus) and of outside diameter Dl which equals or sligh~ly exceeds the diameter of the fully dilated pupil o~ a human eye. As is clear from Figure l, the diameter Dl is very much less than the diame~er D2 of the iris 12 of the eye ll. Generally speaking, the diameter Dl, is in the range 5 to 8mm, and the diameter D2 is in the range of 12 to 14mm~ the latter being the diameter of a conventional contact lens.
Fixed to and centrally supporting the lens element 10 is a haptic 13 of much larger included area than the lens element 10. Haptic 13 comprises two thin sheets 14-15 of plastic material laminated to the front and back surfaces of lens element 10, and to each other in regions radially ou~side element 10; in these outer regions, haptic 13 is characterized by very substantial fenestration, meaning that the structure is primarily "open", for normal air or "breathing" exposure of the surface o:~ the cornea. Such ~9~'7~7 fenestration may be by photographically delineated milling, before or after lamination of the sheets 14-15 to each other, relying upon such chemical-etching, plasma and other milling techniques as are described for intraocular lens haptics, in my United States Letters Patent 4,0~0,70g.
More specifically, each of the sheets of haptic 13 is seen to be o~ generally oval or elliptical outer contour and to comprise four radially outward foot formations, there being a first larger pair 16-17 on the major axis and a second shorter pair 18-19 on ~he minor axis. It is intended that these ~oot formations be very compliant in the axial direction, to render them self-conforming to the surface of the cornea. Each foot formation, taking formation16 as ~ypical, comprises angularly spaced outer legs 20 and a central leg 21 integrally connecting an inner hub portion 22 to an outer bridge portion 23;
and intermedia~e their points of interconnection all these elemental areas are slotted, as at 2~, to render them 0ven more self-confirming to the surface of the cornea. The sheets 14-15 should be selected for auto-clavability and may be of l-mil or 0.5 mil material, suitably nylon, high-density polyethylene, Mylar*, Teflon*, polyethersulfone, polyester, sheet silicone, or H.E.M.A., meaning that in the elemen~al areas 20-21-22-23, the haptic is o~ thickness T
(Figure 6) in the range of 1 to 2 mils; the width Wl of each of these areas is typically in the order of 10 mils, and slot widths W2 are in the order of 3 mils. The overall dimensions of the haptic blank may suitably be 16mm.
(major axis) by 12mm ~minor axis). Bonding o~ the plastic sheets 1~-15 to each other may be by suitable ultrasonic, heating or cemen~ing techniques, as applicable.
Prior to application to the cornea, the foot formations 16-17-18-19 are so a~ially weak ("floppy") as to be apparently useless as supports for * Trade Marks of the DuPont Company ~33'7'~7 the associated lens element 1~. However, once the central lens-bearing region is placed over the pupil~ ~he adjacent floppy hap~ic regions are drawn, by a self-wetting action akin to surface tension and/or capillary attraction (in the context of surface moisture on the cornea) to lie down on the cornea in con:Eormance to locally adjacent curvature of the cornea. In addition to rendering the elemental areas 20-21-22-23 more compliant, tlle slotted regions ~24) thereof achieve a pump-like coaction wi~h surface liquid on the cornea, with the result that surface liquid is locally displaced and drawn into and through the slotted regions (24), and essentially all haptic area radially outside the lens element 10 has an affinity :for the cornea region to which it has "attached" itself by self-wetting. Thus, the relatively narrow and slotted nature of areas 20-21-22-23 promotes displacemen~ of surface liquid, with the attendant benefit of cleaning and lubricating action, particularly when blinking the eyelid over the installed structure. And the 1 to 2-mil haptic thickness encountered by a blinking eyelid is inconsequential, while the lens elemen~ remains sufficiently anchored in its installed eye-axis position, it being further noted that, as a result of using the indicated milling techniques, all edges of the haptic formations are smoothly rounded and therefore not a source of irritation The anchoring effect is enhanced by providing a mildly roughened surface (as by etchin~) on the posterior side of the haptic areas 20-21-22-23, and the smoothness of eyelid action is enhanced by providing a smooth anterior surface of the haptic; the roughened surface will have been created prior to milling and will have a ~lull or matte appearance, and the smooth surface will be shiny, thus enabling ready identification of the front and back surfaces of the assembly.
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In the form of Figures 1 to ~, the sheets 14-15 continuously ~nd intimately cover the respective front and back surfaces Oe lens element 10.
The selected plastic material of sheets 14-15 must therefore be for their transparenc~, and as noted previously, reliance is upon the lens element 10 for optical properties. Generall~, it may be observed that use of plastic material for lens element 10 means an index of refraction substantially less than that of glass. rherefore, production of plastic lens elements 10 will mean greater curvature (shorter radii), and therefore greater lens thickness, than for a glass lens element 10 of the same diopter specification. In the case of the glass lens element 10, optical glasses are commercially available with various indices of refraction in the range 1.4 to 2.0, and I find that by grinding all lens elements 10 ~as optically finished plano-convex elements), with the same single radius of curvature (e.g., 300-mm radius), a full range of prescribable diopter powers (at quarter-diopter increments, up to 10 diopters) is available merely by choice of the glass for its particular index of refraction; a similar single-radius approach in grinding negative-lens surfaces will also serve a wide range of diopter prescriptions, *hrough appropriate selection of a particular glass for its index o refraction.
Further, because glass elements 10 may be finished with prescribable grinding eccentricity, astigmatism correction can be provided, the lens element being oriented with its astigmatic-correction axis rotationally displaced to a prescribed angular orientation with respect to~ say, the major axis 16-17 upon assembly to and lamir,ation with the haptic parts 1~-15; the exposed dull vs. shiny surfaces of the haptic, being recogniæably exposed, enable the user to make sure that his installed lens (major axis horizontal, shiny side facing forward) will always be so installed in his eye as to avoid astigmatic ambiguity.
_ 9 Figure 5 illustrates a modification ~herein each of the haptic sheets 14'-15' is formed with a central aperture of diameter D3, to enable peripheral overlap with the rim of lens element 10; lamination of the sheets 14'-15' and their substantial ~enestration radially outside lens element 10 is otherwise as described for Figures 1 to 4. m e diameter D3 is illustratively 4.5 to 5~n, to allow such peripheral o~erlap to the radial extent of O.S to 0.75mm, for the case of a 6-mm diameter Dl of lens element 10.
Figure 7 depicts an alternative construction, partlcularly suited to eyes for which no astigma~ism is to be corrected. The only significant difference in Figure 7 is that the outer perimeter of the haptic 30 thereof is generally circular. In other words, all foot formations 31-32-33-34 are alike, and preferably comprise slotted elemental hub, foot, and bridge areas corresponding to areas 20-21-22-23 of Figure 2.
Figures 8 and 8A respectively illus~rate circular and elliptically con~oured embodiments of a modified version of the in~ention, particularly suited to the a-tonic iris, i.e., an eye having no iris or a damaged iris.
One or both of the sheets which comprise the haptic 40 (40') is characterized by an opaque a~mular region 41 (41') extending from the lens-lapping inner diameter D3 to an outer diameter D4 to match ~he person's other-eye iris diameter. Foot formations 43-44 (43'-44') extend radially outward of the hub region of lens element retention, but the major open fenestration is radially outside the annulus 41 (41'~, the "opaque" region 41 ~41') being desirably foraminated with apertures of diameter preferably less than substantially 0.005 inch and at least as great as the thickness of region 41 (41'), to permit "breathing" action of the corneal surface covered thereby.
Desirably, the "opaque" region is so finished as to color and design as to '7~7~
create the appearance of a normal iris in the afflicted eye.
~ igures 9 and 9A illustrate modification o~` the respective circular and elliptical embodlments o~ Figures 7 and 2~ wherein the haptic 50 (50') is peripherally continuously a circle or an ellipse or oval. Slotting of elemental areas of haptics 50 (50') is again preferred, as described for Figure 2.
The 10ppy nature of the continuous periphery of both haptics SQ (50') enables continuous intimate attraction to the cornea surface in the manner described for Figures 1 to ~, and the plurality o~ axially compliant radial leg elements 51 (52-53) is preferably at least three~ being shown as four, for both Figures 9 and 9A.
Figures 10 and lOA are directed to an all-glass embodiment oE the invention wherein the lens element 10 is an optically finished element, shown as plano-convex and with a cylindrical rim of thickness T2 in the range 1 to 3 milsJ preferably substantially 2 mils. The flat posterior side of lens element 10 is mo~mted, as by fusing or ~y a suitable cementJ to the central region of a sheet ~lass haptic 60 o~ thickness in the range 0.5 to 1.5 mils, preferably 1 mil. Fenestration is provided in the haptic region external to lens element 10, in the manner discussed above for the forms of Figures 2 and 7, 9 and 9A, as the case may be. The glass haptic 60 is thus substantially as floppy as its plastic counterpart, but it has the advantage of being less susceptible to bacteria-growth phenomena, and therefore less likely or less ; oEten to require removal for cleaning and sterilization; its ultimately flexed curvature in adaptation to the cornea is suggested by dashed lines 60.
~ Figures 11 and 12 illustrate a ~urther embodiment wherein the ; element 10' is a meniscus--lens, having a concave axial-end surface oE first spherical radius Rl and a convex ou~er or opposite-end surface of second spherical radius R2; in the illustration Rl is shown to exceed ~2 and thus to de~ine a positive meniscus~lens 10', bu-t the relation of Rl to R2 will be understood to be dictated by prescription appropr:iate to the op~ical correction needed by a particular eye. The circular periphery of lens element 10' is characterized by a rabbet formation 65, which may be etched, thus establishing a substantially cylindrical land of diameter D5; the land terminates at a radially outward shoulder of outer diameter D6, being the peripheral limit of the lens element. Typically, D6 will be in the range 6.5 to lOmm, and the etched shoulder height ~ R of the rabbet will be 0.1 to 0.25 mm, so that D5 may be 6mm or larger; at the same time, the axial depth T3 of the rabbet may be about 0.05mm, thus constituting a rela~ively harmless incursion upon the rim thickness T4 of the lens element, T~ being abou~ O.lmm, and the ~iml thickness T~ ~see Figure 12) being approximately 0.5mm and of course dependen~ on particular curvature radii Rl and R2. The curvature radii will generally be about 300mm, respectively differing as much as 9mm from each other, it being understood that the sense of the difference determines whether the lens elemen~ 10' is positive or negative.
The haptic 66 to which lens element 10' is assembled is shown flat in Figure 11, since it is an annular blank cut, preferably by etching, from thin sheet material which may ~e glass or a suitable plastic. The cent:ral opening 67 of haptic 66 may be of the diameter D5 of the rabbet land to which it is fitted; whether of glass or plastic, a suitable cemen~ inert to bod~
fluids may be employed to secure the assembled haptic (66) and lens (10') elements. Preferably, however, if haptic 66 is of glass, the diameter of opening 67 is selected for such slight interference with the diameter of the rabbet land that (1) upon heating to expand opening 67J the haptic will ~ 9 ~ t~
insertably receive the rabbet land to the point of circumferential abutment with the rabbet shoulder and (2) upon allowing the thus-assembled parts to cool, a sligh~ residual circumferential tension (clamping) will develop in haptic 66 to permanently retain the assembled relationship.
The preferred material for lens element 10' is optical glass, of selected index o refraction as previously noted. And in that event, the rabbet 65 is preferably the result of suitably masked chemical etching, the etching proceeding axially from one to the exclusion of the other axial end of the lens element; as shown, the rabbet and the rabbet-forming etch involve only the convex end of the lens element. A suitable etchant is hydrofluoric acid, diluted to about 20 per cent in water.
It is a feature of the invention that the lens element 10', although much smaller than those in curren~ contact-lens use, shall be characterized by spaced through-passages, such as passages 68 in Figure 13~ for permitting air access to a corresponding plurality of lens-covered regions of the cornea.
~s shown, in Figure 13, three such passages are provided~ at equal spacing from each other and on a single common geometrical circle of diameter D7 about ` the central optical axis. In Figure l~ such passages are shown equally spaced on each of two concentric circles of diameters D8-D8' about the axis, and is Figure 15, the Dg diameter circle of such passages surrounds a central passage 68' of the same character.
The passages 68-68' of Figures 13 to 15 may suitably be of 0.25 to 0.5mm diameter and the geometrical circle diameters may be in the range of to 8mm, depending on the number and distribution of the passages and the peripheral diameter D6 of the lens element. In any case, however, the combined sectional area of all such passages is preferably less than one per ~ 1 ~'7~7~.'7 cent of the peripherally included area of the lens, so that "breathing" is possible without degrading vision.
~ hile it is possible and highly satisfactory to provide ground optically finished front and back surfaces for a glass lens element 10', this is a relatively expensive technique. My current preference is to use compression dies on a heat-softened blank to form the desired convex and concave surfaces of the lens. Such apparatus is shown, simplifiedJ in Pigure 16. Basically, an annular body 70 pro~ides a straight cylindrical bore 71 of diameter to clear and locate an inserted blank for element 10'. Bore 71 receives a bottom-inserted fixed-die element 72 having an upper convex spherical surface of radius Rl on a central axis 73; at its other end~ bore 71 provides axial guidance for a movable-die element 74 having a lower concave spherical surface of radius R2, also on the central axis. Assuming the prior etching of rabbet 65, a heat-softened flak glass blank for element 10' is inserted in bore 71 (rabbeted side up) so that upon descent of the upper die element 74, the projected rim 75 at the periphery of the concave end of element 74 will locate in the rabbet 65 upon inikial contact with element 10'.
Ihereafter~ compression of die elements 7~-72 squeezes the softened glass blank into its ultimate desired curvatures, dependent of course upon the curvatures associated with the respective convex and concave forming surfaces of the die elements.
What has been described thus far applies to the manufacture of lens elements 10' in which no astigmatic correction is prescribed, namely, meniscus-lens elements in which Rl and R2 are centered on the optical axis of the element 10'. To provide for astigmatic correckion, it is merely necessary that for one of the die elements 72 or 74, the curvakure-forming spherical 77~7 surface thereof shall be based on a center that is offset from the optical axis (i.e.~ ecc0ntric with respect to tlle center o~ the other die-element spherical surface), the extent of the offset being of course a function of the prescrip~ion s~a~ement of degree of correction required. In the event of such eccentric offset, it is convenient to e~ternally indicate the angular direction of the offset, as by appropriate edge marking on the flange 72' (or 7~') of the die element 72 ~or 74~ having the eccentric offset of its spherical center.
The haptic 66 is also preferably etch-cut ~rom thin fla~ sheet glass stock, and is therefore initially as shown in Figure ll. According to one method of assembly, such a glass haptic blank is heat-softened and compression-die formed into dished spherical shape in conformance with cornea curvature, prior to its assembly to the inserted element 10'; such forming is exemplified in Figure 12, being shown after completion of its above-described assembly. It will be understood that the chemical etching by means of which the haptic bla~k is cut from sheet stock may also provide fenestration as desired in the haptic blank. Such fenestration may take one of the forms described in connection with Figures 1 to 9, or it may be o~herwise as desired, for example, foraminated with spaced apertures as described at 68 for lens element lO'.
It is also desirable that either the etched design or the die-forming design operative upon the haptic 66 shall provide a built-in recognizable angular reference identification (indicium) so that the ultimate user can always apply his lens assembly in consistently correct angular orientation; such a die-formed indicium appears at 79 in Figure 12. Recognizable ori~ntation is particu-larly important when the lens element lO' incorporates astigmatism correction, and it will be understood that the angle identification mentioned above in connection with eccentric offset in the die-elemen~ relation mus~ be correctly 7~
positioned with respect to the haptic reference identi.fication (indicium), upon haptic to lens element assembly, the correct angular -rela~ion being as prescribed for the ultimate user's eye.
The described embodiments of the invention will be seen to achieve all stated objects. Importantly, the invention brings light weight and substantially reduced bul~ and surface area to the contact-lens art7 plus the inherent capability of providing optically finished glass lens elements, with astigmatic correction, i needed; further, photochromic glass at lO
provides a hitherto ~mavailable feature in a contact lens configuration.
Fenestration areas are substantial, radially outside the supported lens element 10, being preferably at least four times the end area of the lens element, such area being taken as within effective perimeter limits of the geometric circular or oval ~elliptical) contour to which the foot formations are tangent. Except for the "opaque" annulus ~ ) of Figures 8 and 8A, all other haptic regions and materials are preferabLy clear and transparen~, foot formations of such haptic regions being effectively i.nvisible to the eye of an observer.
Not only does the invention bring above-noted benefits of optically finished glass to the contact-lens art, but an i~portant safety factor is also provided. In embodiments involving plastic-shee~ haptics, the plastic sheets of the haptic fully enclose and support the lens element in at least the region of its rim; in other words, it is at least the most delicate and racturable part of the lens ~hich is protected by such plastic-sheet enclosure.
In glass haptic situations as described in connection with Figures 10 and lOA, the haptic sheet 60, being bonded to lens element 10 over its full area, provides reinforcement to the otherwise more fracturable rim region of the ~ 16 -~ ~'77~7 lens element 10; in the event that lens element 10 is a meniscus-lens, the haptic sheet 60 is preferably centrally open to the diameter D3 (see Figure S), but there will be an annular overlap (Dl, minus D3) within which sheet 69 and lens 10 are bonded, thus providing lens-rim reinforcement, in addition to the described support and positioning flmctions of the haptic. And in the etched-glass situations discussed in connection with Pigures 11 to 15, it wi]l be noted that as a result of chemical etching there is no chipping, nicking or the like degradation of remaining glass, as at the rabbeted periphery, so that inherent strength and resistance to shatter are preserved in the etched glass components.
It should be further observed that although curvatures and diopter ranges have been mentioned by way of illustration, these ranges are in no sense by way of limiting the invention. For example, the invention will be seen to have application to aphakic patients3 i.e., to those whose cataracted natural lens has been surgically removed but for whom an external lens, rather than an implanted intraocular lens, has been prescribed. Such lenses may be of the structure, nature and combinations herein described, but with a stronger finished optical element 10, e.g., having power in the order of 10 or more diopters. When such stronger lenses are of glass, the thickness of the lens i 20 element 10 per se will still be very much less than for a conventional contact-lens prescribed for the same situation.
While the invention has been described in detail for preferred forms shown, it will be understood that modifications may be made without departure from the claimed scope of the invention. For example, the technique of retaining an optical element by and between laminated plastic sheets whi.ch become the haptic lends itself to intraocular-lens application, so that for ~'77~'~
example, a configuration as in Pigure 7, and with three or more foot formations within an outer circular locus of 12 to l~mm diameter may serve well for anterior-chamber implan~ation, relying upon the foot formations to develop stabilizing support at the scleral ridge (adjacent the base of the iris). Of course, in that event, the haptic sheets should provide a more stiff radial-support action, in that they stand without contact analogous -to the described cornea-adherent extraocular applications herein; thus, for intraocular application the overall haptic thickness Tl is preferably about lO mils, and of course lens curvatureswill be of shorter radius in view of the vitreous-humor environment in which such lenses must function.
Claims (32)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A contact-lens assembly adapted for removable mounting to the cornea of an eye, comprising an optically finished lens element having a circular periphery characterized by a peripherally continuous rabbet formation at one axial side of said element, and a single-piece haptic of flexible sheet material having a circular opening at the rim of which said haptic has circumferentially continuous seated engagement with said rabbet formation and thereby mounts said lens element.
2. A contact-lens assembly adapted for removable mounting to the cornea of an eye, comprising meniscus-lens means of optical glass having a circular periphery characterized by a peripherally continuous rabbet formation at one axial side of said lens means, and single-piece annular haptic means of sheet material having a circular opening at the rim of which said haptic means has circumferentially continuous seated engagement with said rabbet formation and thereby mounts said lens means, said haptic means having generally spherically dished convex and concave surfaces at its respective axial ends, the convex surfaces of said haptic means and of said lens means being at the same axial end of said assembly.
3. The lens assembly of claim 2, in which said haptic means is of such thin sheet material as to enable a degree of gently compliant conformance to the curvature of the cornea.
4. The lens assembly of claim 3, in which said haptic means is of glass.
5. The lens assembly of claim 3, in which said haptic means is of plastic.
6. The lens assembly of claim 4, in which said haptic means is in circumferentially tensed engagement with said rabbet formation.
7. The method of making a two-piece contact-lens assembly, wherein a circular lens element having a peripherally continuous rabbet with land and shoulder surfaces at one axial side is engaged at the rabbet to the circular rim of a centrally apertured flexible haptic element of heat-expandible sheet material, which method comprises heating said haptic element to expand the rim circumference of its circular aperture, such expansion being to a degree to permit axial insertion of the rabbet land surface to be engaged, making such insertion to the point of axial location at the shoulder surface of the rabbet formation, and retaining the thus-assembled relation while allowing the haptic element to cool and thus shrink into said tensed engagement.
8. The lens assembly of claim 4, in which said lens means is characterized by a peripherally continuous rabbet formation at one axial side of said lens means, said haptic means being of glass and in circumferent-ially tensed engagement to said rabbet formation.
9. The method of claim 7, wherein both the lens element and the haptic element are of glass.
10. The method of making a glass contact-lens element of meniscus configuration and adapted for assembly to a mounting haptic, which method comprises selecting a thin sheet of optical glass of desired refractive index, chemically etching a circular line to define and separate a lens blank from said sheet, selecting a pair of die elements having cooperating convex and concave surface curvatures appropriate to desired ultimate meniscus-lens curvatures, heating the lens blank to softened condition, forming meniscus curvatures by axially compressing the softened blank between said die elements, and allowing the die-formed blank to cool.
11. The method of claim 10, in which the center of curvature of one of said die elements is eccentric to the axis of die compression, whereby the die-formed blank has an inherent astigmatism-corrective property.
12. The contact-lens assembly of claim 2, in which the center of curvature of one of the meniscus-lens surfaces is eccentric to the center of curvature of the other meniscus-lens surface, whereby said lens means has an inherent astigmatism-corrective property, and in which said haptic means is characterized by a visually observable indicium of a reference location at one angular location about the circle of said opening, said lens means and said haptic means being assembled in angularly oriented relation such that the astigmatism-correction axis bears a particular angular relation to said reference location, said oriented relation being determined by prescription appropriate to the astigmatic condition of the eye to be fitted.
13. The method of making a two-piece glass contact-lens assembly wherein a glass contact-lens element of meniscus configuration is assembled to a dished glass haptic element, which method comprises selecting a thin sheet of optical glass of desired refractive index, chemically etching a circular line to define and separate a lens blank from said sheet, selecting a thin sheet of glass and etching the same to define a blank for the haptic element, assembling both blanks to ultimate co-axial relation, selecting die elements having cooperating convex and concave surface curvatures appropriate to desired ultimate meniscus-lens curvature and to desired ultimate dished haptic curvature, heating the assembled blanks to softened condition, concurrently forming the meniscus curvatures and the haptic curvature by axially compressing the softened blanks between said die elements, by allowing the die-formed assembled blanks to cool.
14. The method of claim 13, in which the haptic-forming concave die surface has an indicium-forming discontinuity at one angular reference-defining location.
15. The method of claim 14, in which the center of curvature of the lens-defining surface of one of said die elements is eccentric to the axis of die compression, the angular location of such eccentricity being so selected in relation to the angular location of said indicium-forming discontinuity that the astigmatism-correction axis of a die-formed lens and haptic assembly is characterized by a prescribed angle, referenced to the indicium and appropriate to the astigmatic condition of the eye to be fitted.
16. The lens assembly of claim 1, in which said lens element is of optical glass.
17. The lens assembly of claim 1, in which said haptic means is of plastic material.
18. The lens assembly of claim 1, in which said haptic means is of glass.
19. The lens assembly of claim 1, in which said lens element is characterized by spaced longitudinally open passages.
20. The lens assembly of claim 19, in which said passages are of diameter substantially in the range 0.25 to 0.5mm.
21. The lens assembly of claim 19, in which said haptic means is characterized by a plurality of spaced longitudinally open passages.
22. The lens assembly of claim 20, in which the number of passages is three or more having a combined effective sectional area which is less than one per cent of the peripherally included area of said lens element.
23. The lens assembly of claim 22, in which a plurality of said passages are at equal angular spacing on a geometric circle about the optical axis of said lens element, the spacing between adjacent passages of said plurality being at least to the magnitude of the radius of the geometric circle.
24. The lens assembly of claim 19, in which one of said pass-ages is on the optical axis of the lens element, a plurality of said passages being angularly spaced on a geometric circle about said axis.
25. The lens assembly of claim 16, in which said rabbet for-mation is the product of chemical etching.
26. The lens assembly of claim 19, in which said lens element is of optical glass and said passages are the product of chemical etching.
27. The lens assembly of claim 26, in which said rabbet for-mation is the product of chemical etching concurrent with the etching of said passages.
28. The lens assembly of claim 16 wherein said lens element is characterized by spaced longitudinally open passages of combined effective sectional area which is less than one per cent of the peripherally included area of said lens element.
29. The lens element of claim 28, in which said rabbet formation and passages are the product of concurrent masked chemical etching from both axial ends of said lens element, the mask on said one axial end being peripherally open to enable rabbet and passage etching from said one end, the mask on the other axial end being peripherally closed to prevent rabbet formation at said other end, and both masks having passage-defining opening which are in longitudinal register to permit concurrent passage formation from both axial ends.
30. The method of making a glass contact-lens element having a circular periphery characterized by a rabbet formation at one axial end, which comprises selecting a thin sheet of optical glass of desired refractive index, cutting a circular blank from said sheet by chemically etching a circular border line to characterize the blank with said circular periphery, chemically etching said rabbet formation from said one axial end, chemically etching in said blank a plurality of spaced longitudinally open passages of combined effective sectional area which is less than one per cent of the peripherally included area of said lens element, heating said blank to soften the same, and compressionally forming front and back lens surfaces on the softened blank.
31. The method of claim 30, wherein the heating and compressive forming steps are performed after the etching steps.
32. The method of claim 30, wherein the heating and compressive forming steps are performed before the etching steps.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US124,941 | 1980-02-26 | ||
| US06/124,941 US4377329A (en) | 1980-02-26 | 1980-02-26 | Contact lens or the like |
| US225,349 | 1981-01-15 | ||
| US06/225,349 US4435050A (en) | 1980-02-26 | 1981-01-15 | Contact lens assembly with haptic and method for making the same |
| CA000371704A CA1160487A (en) | 1980-02-26 | 1981-02-25 | Extraocular contact lens construction |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000371704A Division CA1160487A (en) | 1980-02-26 | 1981-02-25 | Extraocular contact lens construction |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1197717A true CA1197717A (en) | 1985-12-10 |
Family
ID=27166977
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000438358A Expired CA1197717A (en) | 1980-02-26 | 1983-10-04 | Extraocular contact lens construction |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1197717A (en) |
-
1983
- 1983-10-04 CA CA000438358A patent/CA1197717A/en not_active Expired
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |