MULTIFOCAL CONTACT LENS

Abstract: A multifocal contact lens (200) customized for a patient has an anterior side with a power curve defined in part by (i) a central spheric aspheric surface (202), (ii) and inner annular spheric surface (204) contiguous with the central aspheric surface, (iii) a second annular spheric surface (206) contiguous along a radially inner periphery with the inner annular spheric surface, and (iv) an outer annular spheric surface (210) contiguous along a radially inner periphery with the second annular spheric surface. Each of the annular spheric surfaces is concentric or coaxial with the central aspheric surface. The central aspheric surface corresponds to a distance vision correction zone. The inner annular spheric surface corresponds to an intermediate vision correction zone. The second annular spheric surface corresponds to a near vision correction zone, and the outer annular spheric surface corresponds to a distant vision correction zone.

Description: MULTIFOCAL CONTACT LENS Background of the Invention This invention relates to a multifocal contact lens. Bifocal contact lenses are designed to correct or compensate for a condition of advancing age known as "pres¬ byopia." In a presbyopic eye, the ability to focus at near distances, such as the normal reading distance, and in some cases at intermediate distances, is diminished. The loss of focusing capability is due to hardening of the eye's natural crystalline lens material. Generally, multifocal contact lenses (usually either bifocal, trifocal or aspheric) are concentric or segmented in configuration. In a conventional bifocal contact lens of the concentric type, a first, centrally located, circular correc¬ tion zone constitutes either distant or near vision correc¬ tion, while a second annular correction zone surrounding the first zone provides the corresponding near or distance vision correction, respectively. In a conventional bifocal contact lens of the segmented or translating type, the lens is divided into two somewhat D-shaped zones. Usually the upper area is for distance vision correction, whereas the lower area is for near vision correction. Such conventional segmented contact lenses require some sort of movement of the lens relative to the eye to achieve acceptable visual acuity for both distant and near vision. One accepted method of fitting contact lenses is based on taking so called K readings (which measure the center of the cornea) and fitting the center of the contact lens in a predetermined relationship to those readings. This, however, is not the only method of fitting contact lenses. In all conventional bifocal fitting techniques, the bifocal or multifocal contact lenses is optimally designed to be particularly positioned on the cornea. However, it is very difficult in many cases, to position the lens to achieve the required fit. In general, the hardest part of fitting a lens is to position the lens at a desired location on the patient's cornea. Precise fitting of a bifocal contact lens to the eye is crucial in so called simultaneous vision contact lenses where the brain receives both near and far vision input and selects between the near vision input and the far vision input, depending on the desired object(s) of perception. As mentioned above, the segmented bifocal contact lenses translate to some extent on the eye. Such lenses can¬ not be locked onto the cornea. However, for good vision, some stability is necessary. Summary of the Invention The present invention is directed to providing a multifocal contact lens which addresses problems of customiza¬ tion to the individual user's corneal geometry and optical requirements. The contact lens should also address problems in manufacturing. Preferably, the lens is made from a polymer material which provides at least about 10% by weight water after hydration. A multifocal contact lens customized for a patient has, in accordance with the present invention, an anterior side with a power curve defined in part by (i) a central sur¬ face, (ii) an inner annular surface contiguous with the cen¬ tral surface, (iii) a second annular surface contiguous along a radially inner periphery with the inner annular surface, and (iv) an outer annular surface contiguous along a radially inner periphery with the second annular surface. Each of the annular surfaces is concentric or coaxial with the central surface. Preferably, the central surface corresponds to a distance vision correction zone, while the inner annular sur¬ face corresponds to an intermediate vision correction zone, the second annular surface corresponds to a near vision cor¬ rection zone, and the outer annular surface corresponds to a distant vision correction zone. In accordance with another feature of the present invention, at least one of the vision correction zones of the lens is an aspheric zone. In one specific embodiment of the invention, the central zone is an aspheric zone with a standard eccentricity between approximately -0.6 and approxi¬ mately -1.0, preferably approximately -0.8. One or more of the annular zones may be spheric zones. For example, all of the annular vision correction zones may be spheric. Or, alternatively, the inner annular surface may be aspheric and the second and outer annular surfaces spheric. According to other features of the present inven¬ tion, the central surface has a diameter between approximately 1.5 mm and approximately 2.5 mm, the inner annular surface has an outer diameter between approximately 2.0 mm and approxi¬ mately 3.5 mm, the second annular surface has an outer diameter between approximately 2.3 mm and approximately 4.5 mm, and the outer annular surface has an outer diameter between approximately 3.5 and approximately 8.0 mm. In one specific embodiment of the invention, the central surface has a diameter of approximately 2.2 mm, the inner annular surface has an outer diameter of approximately 2.8 mm, the second annular surface has an outer diameter of approximately 3.5 mm, and the outer annular surface has an outer diameter of approx¬ imately 8.0 mm. The anterior side of the lens may have an annular lenticular area with an inner periphery contiguous with the outer annular surface and with an outer diameter between approximately 8.0 mm and approximately 14.5 mm. It is contemplated that the multifocal contact lens has a cornea-fitting posterior surface which has an eccentricity magnitude ranging from 0.0 to about 1.5 and including 0.0. A multifocal contact lens in accordance with the present invention may be manufactured from hydrophilic or soft (hydrogel) polymeric materials i.e., polymeric materials which contain at least about 10% by weight water after hydration, such as disclosed in U.S. Patents Nos. 5,314,960 and 5,314,961, the disclosure of which is hereby incorporated by reference. In accordance with an additional feature of the present invention, where the central surface is aspheric, it has a maximum change in power of approximately 1 diopter from the center radially outwardly to the peripheral edge. The preεent invention relies in part on a method for preparing a customized soft or hydrophilic multifocal contact lens wherein a standard diagnostic hydrophilic contact lens having a predetermined refractive power for distance vision is first placed on the patient's eye and allowed to seat itself in a natural position. The hydrophilic lens of the present invention will generally seat itself in a substantially centered position (which term shall include a somewhat off- centered position). In one step of the method, an over-refraction is performed using the diagnostic lens in its natural position on the patient's cornea to determine a spheric or aspheric power curve which may be applied to a first portion or area of a prescription multifocal contact lens to provide optimal dis¬ tance vision for the patient. In another step, a further over-refraction is performed to determine a second spheric or aspheric curve to provide near vision for the patient. As discussed above, the distance vision area may be a central area of the lens, while the near vision area is an annular area concentric or coaxial with the central area. Alterna¬ tively, the central zone may be a near vision correction zone, while distance vision is corrected by an annular zone located concentrically or coaxially with respect to the central zone. In both cases, a further distance vision correction zone may be provided next to a lenticular area of the lens. The refractive power of this additional zone may be defined in part by a spheric or aspheric surface on the anterior side of the lens conforming to the prescription needs of the individ¬ ual patient. In any event, the outer distance vision correc¬ tion zone is effective to assist in the correction of distance vision under low levels of illumination, for example, during night driving. The patient is fitted with a lens having the same posterior profile as the diagnostic lens and an anterior pro¬ file with two or more concentric or coaxial power surfaces. The anterior power curve will generally comprise at least two and may comprise as many as four spheric and/or aspheric curves to provide adequate vision for near, intermediate and far distances. In certain instances, such as in mature pres- byopes, in order to accommodate near, intermediate and dis¬ tance vision, the prescription lens preferably will comprise central, paracentral and peripheral spheric curves, each having a clinically determined power, or curvature, on the anterior surface of the lens and a single posterior spheric or aspheric curve of predetermined eccentricity, or optionally and preferably, a spheric curve combined with an aspheric curve of predetermined eccentricity. Upon placement of a diagnostic hydrophilic contact lens on the cornea of a patient's eye so that the fitting sur¬ face is in substantial alignment with the cornea, the diag¬ nostic lens usually aligns itself with the cornea in a sub¬ stantially centered position. In this position, the patient may have adequate distance vision. With the appropriate diag¬ nostic lens in place, the patient's near vision will be determined. Over-refraction of the lens for near vision will indicate a power curve to be cut on the anterior side of this lens. The lens which is produced from this process will pro¬ vide intermediate vision, in addition to near and distance vision. However, another over-refraction may be performed to determine the prescriptive strength of an intermediate vision correction zone located on the anterior side of the lens just outside of the central distance vision correction zone. Generally, a diagnostic lens used in a fitting method in accordance with the present invention will have a plurality of concentric or coaxial areas with respective predetermined power curves on the anterior side of the lens. The fitting or lens preparation method described above recognizes the difficulty of providing adequate multifo¬ cal hydrophilic contact lenses. However, instead of strug¬ gling to achieve absolute corneal centering, as some fitting techniques attempt, the instant method obviates the difficulty by assuming that the greatest majority of fitted multifocal lenses will be centered or slightly off-centered on the cornea. In a method in accordance with the present invention, the diagnostic lens positions itself in its natural position, which, in hydrophilic lenses, is centered or substantially centered (slightly off-center). Because the finished lens has the same back surface design as the diagnostic lens, there is no need to further position either the diagnostic lens or the finished product, which should naturally position the same way as the diagnostic lens. The present invention recognizes that each cornea is different and, instead of molding or fitting a lens precisely to center on the eye, the instant contact lens preparation technique selects among a fixed number of prescribed standard fitting or diagnostic lenses and then modifies only the anterior surface in order to achieve an optimal multifocal vision. This method can change differential powers of the two or more concentric or coaxial anterior spheric zones without appreciably affecting the fit. Whenever one refracts over such a lens on the eye using spheric ophthalmic lenses, the patient subjectively chooses that ophthalmic lens power combined with the multi¬ plicity of lens powers in the spheric central zone of the con¬ tact lens which provides the best acuity of vision at both far distance and near distance. There is a cortical interpreta¬ tion of the independent images to determine the best accep¬ table summation of images. The present invention may be used with all standard contact lens materials, i.e. rigid (gas permeable or PMMA), but is preferably used with soft (hydrogel) polymeric materials i.e., polymeric materials which contain at least about 10% by weight water after hydration, such as disclosed in U.S. Patents Nos. 5,314,960 and 5,314,961. Brief Description of the Drawing The sole figure of the drawing is a schematic front elevational view, on an enlarged scale, of a multifocal con¬ tact lens in accordance with the present invention. Detailed Description In preparing a customized multifocal contact lens, a standard diagnostic contact lens is first placed on the patient's eye and allowed to seat itself in a natural, sub¬ stantially centered, position. The anterior side of the lens has a plurality of concentric or coaxial spheric or aspheric surfaces essentially alignable with the cornea of the patient's eye. The posterior side of the lens is formed with a spheric or aspheric surface which is adapted to fit the lens to the cornea of the patient. If, upon placement on the patient's cornea, the diagnostic lens does not produce ade¬ quate distance vision, a first over-refraction is performed to determine a first spheric or aspheric power curve for a cen¬ tral anterior zone of the lens. This central power curve is responsible for correcting distance vision and is provided by modifying a central portion of the anterior surface of a fin¬ ished prescription lens having the same posterior surface as the diagnostic lens. An additional over-refraction is then performed to determine a second power curve for an annular anterior area or zone of the lens to provide adequate near vision correction. The second power curve is formed by modifying an annular portion of the anterior surface of the finished prescription lens. A third, spheric or aspheric, power curve is provided in an annular, outer area of the fin¬ ished lens to assist in the correction of distance vision under low levels of illumination, for example, during night driving. A fourth power curve, to provide correction for intermediate vision, is provided in an annular area on the anterior side of the lens immediately outside of the central power zone. A separate over-refraction procedure may be used to determined the power curve for the intermediate vision cor¬ rection zone. If the above discussed procedure fails to provide satisfactory near and distance vision, a different diagnostic lens may be used to determine power curves where the central zone on the anterior side of the lens is a near vision correc¬ tion zone, while an annular area is a distance vision correc¬ tion zone. The concave cornea-fitting posterior surface of the diagnostic lens and accordingly of a finished prescription lens, is spheric or aspheric with a predetermined eccentricity ranging from, and including, 0.0 to about 1.5. Where one or more surfaces on the anterior side of the diagnostic lens are aspheric, those surfaces have respective standard eccentricities. Generally, those anterior surfaces of the diagnostic lens have different eccentricities. However, it is also possible for them to have the same eccentricity. In fitting a patient with a multifocal contact lens, the diagnostic lens is placed on the cornea of the patient's eye so that cornea-fitting posterior surface is in substantial contact with the cornea. The lens is allowed to align itself with the cornea in a substantially centered position. Upon an alignment of diagnostic contact lens in the substantially centered position, a series of conventional diverging or con¬ verging spheric opthalmic test lenses are disposed before the lens on the patient's eye to determine a power curve with which anterior surface of a central lens portion can be formed to provide optimal distance vision for the patient. A subse¬ quent over-refraction is performed to determine a spheric or aspheric power curve with which an annular surface of the lens may be formed to provide optimal near vision for the patient. To optimize the fitting of a diagnostic lens to any particular patient's cornea, the lens is first selected from a kit of standard diagnostic contact lenses each having concave cornea-fitting posterior surface and an anterior side with a predetermined annular spheric or aspheric surface and a predetermined central spheric or aspheric surface. Most of the lenses in the kit have cornea-fitting posterior surfaces which are spheric or aspheric with eccentricities between 0.0 and about 1.5, inclusive. The patient is fitted first with a diagnostic or fitting contact lens having a posterior surface which substan¬ tially matches the cornea of the patient about the iris. Of course, precise matching is undesirable, because space is required for tear flow, etc. Two or more different standard diagnostic contact lenses may be tested sequentially on the cornea of the patient to determine which has the most appropriate cornea-fitting surface and anterior surfaces. However, a suitable diagnostic lens may be preselected inasmuch as appropriateness of the posterior and anterior surfaces depends in large part on the needs of the particular patient, for example, on whether the lens is to be used primarily for reading, primarily in social situations, or primarily for distance vision correction. In order to secure acceptable distance vision and near vision in a multi-focal contact lens pursuant to the above-described procedure, particularly where there is a signficant difference in "add" between the prescription or power curve for distance vision and the prescription or power curve for near vision, the lens may be formed to float or translate slightly on the cornea to an extent greater than normal. Thus, in the case of a contact lens having two anterior aspheric surfaces, a steeper part of the power curve may be shifted over the pupil for near vision. In the case of a lens with a third, paracentral anterior aspheric surface, the slight translation of the lens may serve to shift the lenticular area more squarely over the pupil for near vision. As depicted in the drawing, a multifocal contact lens 200 customized for a patient has an anterior side with a power curve defined in part by a central surface 202, an inner annular surface 204 contiguous with central surface 202, a second annular surface 206 contiguous along a radially inner periphery 208 with inner annular surface 204, and an outer annular surface 210 contiguous along a radially inner periphery 212 with second annular surface 206. Each of the annular surfaces 204 and 210 is concentric or coaxial with central surface 202. Central surface 202 corresponds to a distant vision correction zone, while inner annular surface 204 corresponds to an intermediate vision correction zone, second annular surface 206 corresponds to a near distance cor¬ rection zone and outer annular surface 210 corresponds to another distant vision correction zone. Central surface 202 has a diameter dl' between approximately 1.5 mm and approximately 2.5 mm, while inner annular surface 204 has an outer diameter d2' between approxi¬ mately 2.0 mm and approximately 3.5 mm. Second annular sur¬ face 206 has an outer diameter d3' between approximately 2.3 mm and approximately 4.5 mm, and outer annular surface 210 has an outer diameter d4' between approximately 3.5 and approxi¬ mately 8.0 mm. An annular lenticular area 214 of lens 200 has no power curve and has an outer diameter d5' between approxi¬ mately 8.0 mm and approximately 14.5 mm. Central surface 202 has a standard eccentricity between approximately -0.6 and approximately -1.0 and more preferably between about -0.75 and about -0.85. Each power surface 202, 204, 208 and 210 may be either aspheric or spheric. In one specific embodiment, cen¬ tral surface 202 and inner annular surface 204 are both aspheric surfaces, with inner annular surface 204 correspond¬ ing to a progressive add zone having a standard eccentricity between approximately -1.5 and approximately -5.0 and, more preferably between approximately -3.0 and approximately -5.0. In this embodiment, annular surfaces 206 and 210 may be spheric or aspheric. In a particular geometrical configuration of this specific corneal contact lens, diameters dl' through d5' are approximately 2.2 mm, approximately 2.8 mm, approximately 3.5 mm, approximately 8.0 mm, and approximately 14.5 mm, respec¬ tively. Central surface 202 has an eccentricity of approxi¬ mately -0.8, while inner annular surface 204 has a standard eccentricity of approximately -5.0. Where central surface 202 is aspheric, it preferably has a maximum change in power of approximately 1 diopter from the center radially outwardly to its peripheral edge 216. Where inner annular surface 204 is an aspheric progressive-add zone, it preferably has a maximum change in refractive power of approximately three and one-half diopters as measured radially from edge 216 to periphery 208. Multifocal contact lens 200 has a spheric or aspheric cornea-fitting posterior surface (not designated), with an eccentricity magnitude ranging between (and including) 0.0 and about 1.5. Multifocal contact lens 200 may be manufactured from hydrophilic or soft (hydrogel) polymeric materials i.e., polymeric materials which contain at least about 10% by weight water after hydration, such as disclosed in U.S. Patents Nos. 5,314,960 and 5,314,961, the disclosure of which is hereby incorproated by reference. Central surface 202 corrects distance vision particularly under conditions of high illumination, while outer annular surface 210 corrects distance vision particularly under conditions of low illumination such as night driving. Surface 204 corrects vision for intermediate distances. Lens 200 is fitted as described above, using a diag¬ nostic or test lens with the same posterior surface as lens 200 and an anterior side with a central spheric or aspheric surface of a predetermined standard eccentricity and power and at least one annular spheric or aspheric surface of a predetermined standard eccentricity and power. Power curves for central surface 202 and outer annular surface 210 are determined, as discussed above, during a first over-refraction procedure wherein a diagnostic or test lens is placed on the cornea of the patient's eye. A power curve for second annular surface 206 is determined during a second over-refraction pro¬ cedure. The power curves for central surface 202 and outer annular surface 210 may be determined under high illumination and low illumination levels, respectively. The power curve for paracentral or progressive-add surface 204 is determined by the preselected standard eccentricity of that intermediate zone and by the results of the first (distant vision) over- refraction procedure. Any progressive add zone (eccentricity of high magnitude) will provide a continuous range of powers to the retina and the brain of the patient. The patient's visual cortex selects from among that continuous range of powers or adds to obtain a focused sight. It is to be noted that in some circumstances, the outer two annular surfaces or correction zones 206 and 210 may be omitted in a prescription lens. Such a simplified lens has only a central aspheric surface 202 and an annular progressive add surface or zone. The central aspheric surface has a diameter between about 1.5 mm and about 2.8 mm, while the annular progressive add zone has an outer diameter between about 1.5 mm and about 8.0 mm. The progressive add zone has a standard eccentricity having a magnitude between approximately 1.5 and approximately 5.0. Where the central aspheric surface corresponds to a distance vision correction zone, the annular surface is an aspheric surface corresponding to a progressive add zone with a standard eccentricity between approximately - 1.5 and approximately -5.0. In another modification of the illustrated contact lens, only the outer annular zone 210 is omitted. In another specific embodiment of the multifocal contact lens of the drawing, central surface 202 is aspheric while inner annular surface 204 is spheric instead of aspheric. In this embodiment, the inner annular surface still corresponds to an intermediate vision correction zone. The radius of curvature of spheric surface 204 is determined by an over-refraction procedure during a diagnostic evaluation as described in detail elsewhere herein. In yet another specific embodiment of the multifocal contact lens shown in the drawing, all of the power curves are spheric, i.e., surfaces 202, 204, 206 and 210 are spheric sur¬ faces with radii of curvature determined by over-refraction procedure during a diagnostic evaluation. In this alternative multifocal contact lens, the surfaces 202, 204, 206 and 210 still correspond to distance, intermediate, near, and distance vision corrections zones, respectively. The widths of the surfaces, in the radial direction, are as set forth above. In an alternative lens having the general geometri¬ cal configuration described above, the central surface cor¬ responds to an aspheric near vision correction zone with a standard eccentricity between approximately +1.5 and approxi¬ mately +5.0 and preferably between approximately +3.0 and approximately +3.5, whereas the inner annular surface is aspheric with a standard eccentricity between approximately +1.5 and approximately +3.5 and preferably about +2.5. The second annular correction surface is also aspheric and has a standard eccentricity between approximately +0.3 and approxi¬ mately +1.0 and preferably approximately 0.8. In such a lens, the central aspheric correction zone has a diameter between about 1.1 mm and about 2.2 mm, while the inner annular surface has an outer diameter between about 1.1 mm and about 2.5 mm. The second annular surface has an outer diameter between about 2.0 mm and 8.0 mm. Usually, a lens with a central near vision correction zone will have only three vision correction zones, although a fourth zone may be appropriate in some cases. An eccentricity between 0.0 and about 1.5 for the cornea-fitting posterior surface of a diagnostic hydrophilic lens or a finished prescription lens is in accordance with the generally aspheric topographical characteristics of the human cornea. With such an eccentricity, the cornea-fitting posterior surface is fitted relatively tightly to the patient's eye, so that the lens, which may move slightly with eye and eyelid movement, does not move significantly with movement of the upper eyelid. Upon the completion of the over-refraction process, the patient is fitted with a prescription lens 200 (generally, from a lens production laboratory) which is substantially identical to the finally used diagnostic lens. The prescrip¬ tion lens may have two anterior aspheric surfaces or three (or more) anterior aspheric surfaces. The anterior surface of the selected lens blank is machined or, more specifically, lathed to produce the appropriate anterior surfaces 202, 204, 206, 210. Alternatively, either the posterior or anterior surface of the lens or the entire lens, including posterior and anterior surfaces, may be molded. In most cases, over-refraction of the diagnostic lens will provide adequate vision for near, intermediate and far distances. In such a case, a lens having a posterior sur¬ face with a single spheric or aspheric curve may be used with good success. By incorporating the features of the contact lenses, it is now possible to avoid having to fit the patient in a rigid set or established position, thus obviating one of the more difficult problems of bifocal/multifocal contact lens fitting. Instead, the fit or position of the lens is first established naturally and thereafter, the visual character¬ istics of the lens are designed into the finished lens. Generally, as is well known in the art, if the anterior power curve is decreased by 12 lines for each diop¬ ter, the add is 1.0. A decrease of 6 lines for each 1/2 diop¬ ter results in an add of 0.5, while a decrease of 24 lines for each 2 diopters results in an add of 2.0. Similarly, a decrease of 48 lines for each 4 diopters results in an add of 4.0. This rule of thumb is helping in guiding the prac¬ titioner to design a lens which can accommodate varying powers of the lens in predetermined distances for maximum fit and visual effectiveness. Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the draw¬ ings and descriptions herein are profferred by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.

Claims: CLAIMS : 1. A multifocal contact lens customized for a patient, having an anterior side with a power curve defined in part by (i) a central surface, (ii) an inner annular surface contiguous with said central surface, (iii) a second annular surface contiguous along a radially inner periphery with said inner annular surface, and (iv) an outer annular surface con¬ tiguous along a radially inner periphery with said second annular surface, each of the annular surfaces being concentric or coaxial with said central surface, said central surface corresponding to a distance vision correction zone, said inner annular surface corresponding to an intermediate vision cor¬ rection zone, said second annular surface corresponding to a near vision correction zone, and said outer annular surface corresponding to a distant vision correction zone. 2. The lens defined in claim 1 wherein at least one of said central surface, said inner annular surface, said sec¬ ond annular surface, and said outer annular surface is an aspheric surface. 3. The lens defined in claim 2 wherein said central surface is an aspheric surface. 4. The lens defined in claim 3 wherein said central surface has a standard eccentricity between approximately -0.6 and approximately -1.0. 5. The lens defined in claim 4 wherein said central surface has an eccentricity of approximately -0.8. 6. The lens defined in claim 3 wherein said central surface has a diameter between approximately 1.5 mm and approximately 2.5 mm, said inner annular surface has an outer diameter between approximately 2.0 mm and approximately 3.5 mm, said second annular surface has an outer diameter between approximately 2.3 mm and approximately 4.5 mm, and said outer annular surface has an outer diameter between approximately 3.5 and approximately 8.0 mm. 7. The lens defined in claim 6 wherein said central surface has a diameter of approximately 2.2 mm, said inner annular surface has an outer diameter of approximately 2.8 mm, said second annular surface has an outer diameter of approxi¬ mately 3.5 mm, and said outer annular surface has an outer diameter of approximately 8.0 mm. 8. The lens defined in claim 7 wherein said anterior side has an annular lenticular area with an inner periphery contiguous with said outer annular surface and with an outer diameter between approximately 8.0 mm and approximately 14.5 mm. 9. The lens defined in claim 3, further comprising a cornea-fitting posterior surface with an eccentricity mag¬ nitude in a range including 0.0 and extending between 0.0 and about 1.5. 10. The lens defined in claim 3 wherein said inner annular surface, said second annular surface and said outer annular surface are all spheric surfaces. 11. The lens defined in claim 3 wherein said central surface has a center and a substantially circular peripheral edge, said central surface having a maximum change in power of approximately 1 diopter from said center radially outwardly to said peripheral edge. 12. The lens defined in claim 2 wherein said inner annular surface is an aspheric surface. 13. The lens defined in claim 12 wherein said second annular surface and said outer annular surface are both spheric surfaces. 14. The lens defined in claim 2 manufactured from a hydrophilic polymer. 15. The lens defined in claim 2 wherein at least one of said central surface, said inner annular surface, said sec¬ ond annular surface, and said outer annular surface is a spheric surface. 16. The lens defined in claim 1 wherein said central surface has a diameter between approximately 1.5 mm and approximately 2.5 mm, said inner annular surface has an outer diameter between approximately 2.0 mm and approximately 3.5 mm, said second annular surface has an outer diameter between approximately 2.3 mm and approximately 4.5 mm, and said outer annular surface has an outer diameter between approximately 3.5 and approximately 8.0 mm. 17. The lens defined in claim 16 wherein said cen¬ tral surface has a diameter of approximately 2.2 mm, said inner annular surface has an outer diameter of approximately 2.8 mm, said second annular surface has an outer diameter of approximately 3.5 mm, and said outer annular surface has an outer diameter of approximately 8.0 mm. 18. The lens defined in claim 17 wherein said anterior side has an annular lenticular area with an inner periphery contiguous with said outer annular surface and with an outer diameter between approximately 8.0 mm and approxi¬ mately 14.5 mm. 19. The lens defined in claim 18, further comprising a cornea-fitting posterior surface with an eccentricity mag¬ nitude in a range including 0.0 and extending between 0.0 and about 1.5. 20. The lens defined in claim 1 wherein at least one of said central surface, said inner annular surface, said sec¬ ond annular surface, and said outer annular surface is a spheric surface. 21. The lens defined in claim 20 wherein said second annular surface is a spheric surface. 22. The lens defined in claim 20 wherein said outer annular surface is a spheric surface. 23. The lens defined in claim 20 wherein said cen¬ tral surface, said inner annular surface, said second annular surface and said outer annular surface are all spheric sur¬ faces. 24. The lens defined in claim 1 wherein said anterior side has an annular lenticular area with an inner periphery contiguous with said outer annular surface. 25. The lens defined in claim 1, further comprising a cornea-fitting posterior surface with an eccentricity mag¬ nitude in a range including 0.0 and extending between 0.0 and about 1.5. 26. The lens defined in claim 1 manufactured from a hydrophilic polymer. 27. A multifocal contact lens customized for a patient, having an anterior side with a power curve defined in part by (i) a central surface, (ii) an inner annular surface contiguous with said central surface, (iii) a second annular surface contiguous along a radially inner periphery with said inner annular surface, and (iv) an outer annular surface con¬ tiguous along a radially inner periphery with said second annular surface, each of the annular surfaces being concentric or coaxial with said central surface, said inner annular sur¬ face corresponding to an intermediate vision correction zone. 28. The lens defined in claim 27 wherein at least one of said central surface, said inner annular surface, said second annular surface, and said outer annular surface is an aspheric surface. 29. The lens defined in claim 28 wherein at least one of said central surface, said inner annular surface, said second annular surface, and said outer annular surface is a spheric surface. 30. The lens defined in claim 27 wherein at least one of said central surface, said inner annular surface, said second annular surface, and said outer annular surface is a spheric surface. 31. The lens defined in claim 30 wherein said cen¬ tral surface, said inner annular surface, said second annular surface, and said outer annular surface are all spheric sur¬ faces. 32. The lens defined in claim 27 wherein said cen¬ tral surface corresponds to a distance vision correction zone.

Inventors: POSTER MAURICE, SEIDNER LEONARD, POSTER, MAURICE, SEIDNER, LEONARD
Applicants: PERMEABLE TECH INC, PERMEABLE TECHNOLOGIES, INC.
Application year: 1996
Main classification: G02C7
IPC codes: B29D11, G02C7