SIMULTANEOUS MULTIFOCAL CONTACT LENS AND METHOD OF UTILIZING SAME FOR TREATING VISUAL DISORDERS

Abstract: A simultaneous multifocal contact lens (10) for correcting vision acuity of an individual is disclosed. The contact lens comprises a central region (25) radially surrounded by at least one far vision focal region (30) and at least one near vision focal region (26), wherein a near vision additional correction of the at least one near vision focal region (26) is ovecorrected by at least 10 % with respect to the near vision additional correction prescribed for the individual according to the standard prescription for lens radius design.

Description: I SIMULTANEOUS MULTIFOCAL CONTACT LENS AND METHOD OF UTILIZING SAME FOR TREATING VISUAL DISORDERS FIELD AND BACKGROl 1ND OF THE INVENTION The present invention relates to a multi focal lens capable of providing a wearer with a focused vision in a range of distances and of a method of utilizing same for treating an indi\ idual suffering from a \ isual disorder such as presbyopia. More particularly, the present inv ention relates to a simultaneous multifocal contact lens which employs overcorrection of a near vision additional correction of a peripheral near vision focal region to thereby provide a wearer with a complete range of focused vision, in particular focused near vision. As an individual advances in years, tv pically past 40-45. a physiologic loss of accommodation in the eyes begins. This physiological loss, which is termed presbyopia, is characterized by an inability to focus on objects that are relatively near to the individual (typically less then 22 cm). In addition to aging, a variety of eye disorders, such as. for example, cataract, which often necessitates lens replacement, can also abolish an indiv idual's ability to focus throughout a range of distances. To correct the loss of a vision range, individuals rely upon spectacles. contact lenses or ophthalmic lens (in the case of lens replacement) having a number of di fferent regions with different optical powers in order to find the appropriate optical power for the object or objects upon w hich the observer wishes to focus. With spectacles, the process involves shifting the field of vision from typically an upper lens portion far power to a lower lens portion near power. With contact lenses, however, this approach has been less than satisfactory. The prior art teaches two types of contact lens designs for the correction of presbyopia, alternating (or translating) and simultaneous. The design of alternating (or translating) lenses is very similar to bifocal eyeglass lenses in that the wearer sees through the distance segment in the upper portion of the lens when looking straight ahead and sees through a lower near vision seszment when the eve is moved to look down. The translation from distance to near in these lenses is achieved through the mechanical action of the lens resting on the lower ey elid and, when the eye looks down, the lens remains stable on the lower eyelid causing the pupil of the eye to translate from the distant vision portion of the lens to the near vision portion of the lens. As such, w hen fabricated from soft materials, numerous operational problems plagued these lenses which have, therefore, enjoyed very limited commercial success. The design of simultaneous v ision bifocal or multi focal contact lenses is either concentric or aspheric with focal pow er changing through di fferent areas of the lens. These lenses are fitted so that distance, intermediate and near zones focus images simultaneously on the retina of the eye and the brain then separates out the image desired. Theoretically, with adaptation, the ability to change focus naturally from near to far w ith no blurring in betw een can be achieved with simultaneous vision lenses. As alternating presbyopic designs proved to be unsuccessful in soft contact lens designs, most of the development work with soft contact lenses was done in the area of simultaneous presbyopic correction with concentric designs or aspheric designs. Numerous examples of simultaneous bi focal contact lenses or ophthalmic lens exist in the art. For example. U.S. Pat. No. 4.923.296 to Erickson describes a lens system which comprises a pair of contact lenses, each having equal areas of near and distant optical power, with the lens for one eye having a near upper half and a distant lower half and the lens for the other eye having a distant upper half and near lower half. Together they provide at least partial clear images in both eyes, and through suppression by the brain of the blurred images, allow alignment of the clear images to produce an in-focus image. U.S. Pat. No. 4.890.913 to de Carle describes a bifocal contact lens comprising a number of annular zones having different optical powers. The object in the design of this lens is to maintain, at all times, regardless of pupil diameter, an approximately equal division between near and distant powers, which requires between six and twelve total zones on the lens. Another attempt at providing a bifocal contact lens is described in U.S. Pat. No. 4.704.016 to de Carle. Again, this lens attempts to maintain, at all times, regardless of pupil diameter, an approximately equal division between near and distant powers. Yet another attempt at providing a bifocal contact lens is described in U.S. Pat. No. 5.929.969. This lens comprises a number of circular ring zones of two optical powers. Although the above described bi focal lenses provide some vision correction, a mismatching of the various optical zones may lead to destructive interference and thus a less than optimal vision in some instances. In addition to bi-focal lenses, a number of multifocal lenses which attempt to improve upon their bi focal counterparts have also been described. For example. U.S. Pat. No. 5.448.3 12 describes a multifocal concentric ophthalmic lens for presbyopic patients constructed with three general annular lens portions in a multifocal design. A central circular portion of the lens has only the patient's distance corrective power, and is surrounded by a first inner annular portion, w hich can consist of multiple annular rings having an inner radial portion which enhances the patient's near focal power encircled by radial portions of substantially equal cumulative amounts of distance and near optical power focal correction for the patient. This is surrounded by a second outer annular portion, w hich can also consist of one or more annular rings having additional distance focal power near the periphery of the optical surface area of the ophthalmic lens. Each annular ring has cither a near or distance optical power and works in combination with other lens portions to yield the desired focal ratio in that portion of the lens. U.S. Pat. No. 5.682.223 describes a multifocal lens design with near, far and intermediate optical power zones. The borders of these zones are optimized for pupil size as a function of lighting conditions. In this design, zone placement and zone radii are not carefully planed and as such destructive interference cannot be avoided. To overcome interference problems. U.S. Pat. No. 5.982.543 describes a multi refractive zone lens optimized with consideration for phase match between the zones. However, the lens design described features lens coherence properties in visible light w hich vary considerably from one scene to the next. Although some of the abov e described lenses have traversed some of the limitations inherent to multifocal lenses, these lenses still provide sub-optimal ision correction for some or all ision ranges. The abov e described prior art designs, be it aspheric or concentric, cannot provide monocular multifocal correction for moderate to mature presbyopia. In most cases, some form of modified mono ision is required in an attempt to satisfy the v isual requirement for near and far v ision. Po address this and other problems ty pical of prior art simultaneous multi focal lenses a variety of lenses w ith under or over corrected focal regions have been described. For example. U.S. Pat. Nos. 5.864.378 and 5.864,379 describe a contact lens and an opthalmic lens (respectively) in w hich a central near vision zone ('379), or both a central near ision zone and a peripheral far \ ision zone ('378) are ov ercorrected. According to these patents, while such a correction does not impair distance vision, it compensates for presbyopia and therefore al lows a user to focus on objects w ithin a range of near and intermediate distances. U.S. Pat. Nos. 5.919.229 and 5.702.440 both describe contact lenses with undercorrected peripheral near v ision zones. Although these lenses substantially enhance the focus range of an individual as compared to other prior art designs, such lenses still suffer from limitations which arise from the nature of the correction or the lens position of the vision region which is corrected. As such, these prior art lens designs cannot completely compensate for moderate to severe presbyopia, thus resulting in a less than a complete range of focused vision. There is thus a widely recognized need for. and it would be highly advantageous to have, a simultaneous multifocal lens which can overcome presbyopia, thus providing a complete range of focused vision, in particular focused near vision, while at the same time having a relatively short period of visual adjustment and being comfortable to the wearer. SUMMARY OF H IE INVENTION According to one aspect of the present invention there is provided a simultaneous multifocal contact lens for correcting ision acuity of an individual, the contact lens comprising a central region radially surrounded by at least one far vision focal region and at least one near vision focal region, wherein a near vision additional correction of the at least one near v ision focal region is overcorrectcd by at least 10 % w ith respect to the near ision additional correction prescribed for the indiv idual according to a standard prescription for lens radius design. According to another aspect of the present invention there is pro ided a method of improving v isual acuity in an indiv idual suffering from presbyopia, the method comprising the steps of (a) fabricating, according to a prescription of the individual, a pair of simultaneous multi focal contact lenses each including a central region radially surrounded by at least one far vision focal region and at least one near vision focal region, w herein a near v ision additional correction of the at least one near v ision focal region is overcorrectcd by at least 10 % with respect to the near v ision additional correction prescribed for the indiv idual according to a standard prescription for lens radius design; and (b) fitting the individual with the pair of simultaneous multifocal contact lenses to thereby improve the isual acuity of the indiv idual. According to further features in preferred embodiments of the invention described below, the near v ision additional correction of the at least one near vision focal region is overcorrectcd by 1 0 to 100 % with respect to the near vision additional correction prescribed for the individual according to the standard prescription for lens radius design. According to still further features in the described preferred embodiments the near vision additional correction of the at least one near vision focal region is overcorrectcd by 15 to 70 % with respect to the near vision additional correction prescribed for the individual according to the standard prescription for lens radius design. According to still further features in the described preferred embodiments the near vision additional correction of the at least one near vision focal region is overcorrectcd by 20 to 50 % with respect to the near vision additional correction prescribed for the individual according to the standard prescription for lens radius design. According to still f urther features in the described preferred embodiments a surface of the simultaneous multifocal contact lens which lies adjacent to a cornea of the individual is quadrically aspherical ly shaped with substantially identical eccentricity throughout and a substantially constant radius for each of the at least one near and the at least one far ision focal regions. According to still further features in the described preferred embodiments the at least one near and the at least one far vision focal regions are each shaped as distinct rings. According to still further features in the described preferred embodiments the focal regions radiate outwardly from the central region in an alternating sequence including the far vision focal region and the near vision focal region. According to still further features in the described preferred embodiments the sequence is repeated at least twice. According to still further features in the described preferred embodiments the sequence is repeated at least three times. According to still further features in the described preferred embodiments the focal regions radiating outwardly from the central region are positioned 1 .125, 1 .275, 1 .525, 1 .675, 1 .9 and 4.0 mm from a center of the central region. According to still f urther features in the described preferred embodiments the simultaneous multifocal lens further comprising a tri-focal diffractive microrclief profile region being positioned at an outermost region of the simultaneous multifocal lens and being for ensuring in-phase interference of the at least one near vision focal region and the at least one far vision focal region when each being at a proper focus. According to still further features in the described preferred embodiments the simultaneous multifocal contact lens further comprising at least one intermediate vision focal region radially surrounding the central region. According to still further features in the described preferred embodiments a surface of the simultaneous multifocal contact lens which lies adjacent to a cornea of the individual is quadrically aspherically shaped with substantially identical eccentricity throughout and a substantially constant radius for each of the at least one near, the at least one intermediate and the at least one far vision local regions. According to still further features in the described preferred embodiments the at least one near, the at least one intermediate and the at least one far ision focal regions arc each shaped as distinct rings. According to still further features in the described preferred embodiments the focal regions radiate outwardly from the central region in an alternating sequence including the far vision focal region, the intermediate vision focal region and the near vision focal region. According to still further features in the described preferred embodiments the sequence is repeated at least twice. According to still further features in the described preferred embodiments the sequence is repeated at least three times. According to still further features in the described preferred embodiments the near and intermediate f ocal regions radiate outwardly from the central region in an alternating sequence. According to still further features in the described preferred embodiments the sequence is repeated at least twice. According to still further features in the described preferred embodiments the sequences are surrounded by the at least one far vision focal region. According to still further features in the described preferred embodiments the focal regions radiating outwardly from the central region are positioned 1.275, 1.525. 1 .675, 1 .9 and 4.0 mm from a center of the central region. According to still further features in the described preferred embodiments the simultaneous multifocal lens further comprising a tri-focal di ffractive microrelief profile region being positioned at an outermost region of the simultaneous multifocal lens and being for ensuring in-phase interference of the at least one near vision focal region, the at least one intermediate v ision focal region and the at least one far vision focal region w hen each being at a proper focus. According to still f urther features in the described preferred embodiments the central region is a far ision focal region. According to still further features in the described preferred embodiments the central region is a near v ision focal region. According to still further features in the described preferred embodiments the near v ision additional correction of the central region is as prescribed for the individual according to the standard prescription for lens radius design. The present invention successfully addresses the shortcomings of the presently know n configurations by providing a multi focal lens capable of providing a wearer with a focused vision in a range of distances which is superior over prior art designs because apparently it accounts for distortions of base curve radii for near vision optical regions associated with contacting the lens w ith an ev e. BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, w ith reference to the accompanying drawings. With specific reference now to the draw ings in detail, it is stressed that the particulars show n are by way of example and for purposes of illustrativ e discussion of the preferred embodiments of the present invention only, and are presented in the cause of prov iding what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the drawings: FIG. 1 is a front v iew of a simultaneous multifocal contact lens according to the teachings of the present inv ention; FIG. 2 is a side v iew of one half of the simultaneous multifocal contact lens according to the teachings of the present invention; FIG. 3 depicts simultaneous focusing of an image by three types of focal regions of the simultaneous multifocal contact lens according to the teachings of the present invention; FIG. 4 is a graph depicting coordinates of optical regions of the simultaneous multifocal contact lens according to the teachings of the present invention and their respective optical power distribution; FIG. 5 is a graph representing a sag di fference betw een smooth and piecewise smooth curves of the simultaneous multi focal contact lens according to the teachings of the present invention; FIG. 6 is a graph representing a magnified v iew of the sag difference between smooth and piecewise smooth curves in a portion of the simultaneous multifocal contact lens according to the teachings of the present invention; FIG. 7 illustrates an optical scheme for light propagation through regions of the simultaneous multifocal contact lens according to the teachings of the present invention; FIG. 8 illustrates light diffraction on a curv ed surface of the simultaneous multifocal contact lens according to the teachings of the present invention; and FIG. 9 illustrates a tilt of an element of the curved surface of the simultaneous multifocal contact lens according to the teachings of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is of a multifocal lens and a method of utilizing same for treating an individual suffering from a visual disorder such as. for example, presbyopia. Specifically, the present invention is of a simultaneous multifocal contact lens which employ s overcorrection of a near v ision additional correction of a peripheral near vision focal region and can be used to provide a wearer suffering from a v isual disorder, such as presbyopia, w ith a complete range of focused vision, in particular focused near v ision. The principles and operation of the present invention may be better understood w ith ref erence to the drawings and accompanying descriptions. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. Referring now to the drawings. Figures 1 -3 illustrate the simultaneous multifocal contact lens for correcting vision acuity of an indiv idual suffering from, for example, presbyopia, according to the present invention, which is referred to hereinunder as lens 10. As is speci fically shown in Figure 1. lens 10 is substantially circular in shape with a typical diameter of between 9 and 14 mm which depends largely on the iris si/e and corneal shape of the indiv idual fitted. Lens 10 is ty pically manufactured in sizes such as large, medium and small, w ithin the above range. As used herein the phrase "substantially circular" refers to a circular structure w hich is fabricated as close to a perfect circle as possible by presently practiced methods of lens manufacturing. As is speci fically show n in Figure 2. lens 10 includes a front surface 12 which faces away from the cornea of the individual fitted with lens 10 and a back surface 14 which lies against the individual ' s cornea when lens 10 is fitted. Both front 12 and back 14 surfaces include an optical zone 16 and a non-optical zone 18 (lenticular zone on front 12 and peripheral zone on back 14 surfaces) w hich are curved in shape. Lens 10 further includes a center 20 and an edge 22. wherein the distance therebetween defines the radius of lens 10. Lens 10 can be fabricated from any standard contact lens materials, i.e.. I 1 rigid (gas permeable or PMMA) or soft (hydrogel). According to the present invention, lens 10 is preferably fabricated from soft poly meric materials i.e.. polymeric materials which contain at least 10 % by weight water after hydration. such as disclosed in U.S. Pat. Nos. 5.3 14.960 and 5.3 14.96 1 w hich are incorporated herein by reference. Lens 10 can be fabricated using methods know n in the art. such as for example, single-path diamond-turning. As used hereinbelow. the terms "near", "far" and "intermediate" when used with reference to focal regions 24 and/or region 25 of lens 10 refer to a distance from the eye which can be focused thereby. Thus, for example, a near vision focal region is configured with an optical or focal power ( -() diopters) capable of correcting v ision in indiv iduals suffering from near vision sight problems ( e.g.. far-sightedness). As used herein the phrases "focal power" or "optical power" when used with reference to focal region 24 or focal region 25 of lens 10 interchangeably refer to the ability of these regions to refract and thus focus incoming light. As specifically shown in Figure 1. optical zone 16 of lens 10 includes several distinct focal regions 24 preferably arranged as concentric rings surrounding a substantially circular central region 25. Region 25 which is positioned in the center of lens 10 can be configured with an optical power for providing focused near vision ( 0 diopters of addition ) or far vision ( ' 0 diopters of addition ). Preferably region 25 of lens 10 of the present invention is a far vision focal region and thus serves for bringing into focus objects which are positioned far from the individual fitted with lens 10 (typically and preferably more than 600 cm). According to the present invention, regions 24 include near vision 26. and far v ision 30 focal regions. Regions 26 and 30 are configured of an optical power capable of bringing into focus objects situated either near (typically between 20 to 40 cm) or far (typically more than 600 cm) from the eye of the individual. Preferably, regions 24 also include at least one intermediate vision focal region 28 which serves to bring into focus objects placed within a distance range of 40 to 200 cm away from the eye of the individual fitted with lens 10. It wil l be appreciated, that numerous examples to contact lenses w hich include a central focal portion surrounded by concentric focal regions are known in the art. As is further detailed in the Background section above, some of these prior art lenses also employ over or under correction of focal regions. specifically under correction of peripheral far focal regions or overcorrection of a central near focal region. Although such corrections substantial ly improve the ability of a contact lens to focus objects positioned throughout a distance range, some limitations still apply. especially when such prior art configurations are applied to soft (hydrogel ) contact lenses. Without an intention of being limited by any theory , based on the assumption that a soft contact lens distorts to conform to the shape of the cornea, and assuming that a change in a radius for near focus regions is performed at the base curve, the front curv e of front surface 12 at the peripheral near v ision focal regions will replicate these changes only to a certain degree. Thus, a compensation for the near focal regions must be applied by providing additional focal power to these regions (overcorrection). Due to higher distortion at the lens periphery, this overcorrection must increase outwardly from the center of the radius. The amount of overcorrection is determined by the distortion of the lens which is governed by the lens material and it's thickness. Near vision addition powers are referred to by eye care professionals as "add" power, and represent the difference between the distance correction and near correction prescribed by an eye care professional for eyeglasses or contact lenses. Accordingly, a prescription of "-3 w ith a +2 add" (which would be typical for moderate presbyopia) would mean that distance v ision requires -3 diopters of correction, and near vision requires an additional 2 diopters of plus correction, resulting in - 1 diopters of near vision correction. While reducing the present invention to practice it was uncovered that with typical lens materials, typical overcompensation of about 30 % additional focal power to the near focal regions unexpectedly improves near eye sight of fitted individuals. Thus, a lens focal configuration which employs over correction of the additional correction ( "add") component of a near vision peripheral focal region by approximately 30 % was found to be far superior to the prior art configuration mentioned hereinabove since such a configuration compensates for the lack of focal power of the peripheral near vision focal regions w hich due to lens distortion are ty pically under-pow ered when worn ov er the eye. 1 hese considerations are discussed in greater detail in the Example pro ided hereinbelow. Thus, according to preferred embodiments of the present invention, the additional correction ( "add" ) used to determine the focal power of near v ision focal region(s) 26 is overcorrectcd by at least 10 %. preferably 10 - 100 %. more preferably 1 5 to 70 %. most preferably 20- 50 % w ith respect to the near v ision additional correction prescribed for the indiv idual as determined by the standard prescription for lens radius design ( lens maker formula). It w ill be appreciated that optical zone 16 can include any number of regions 26. 28 and/or 30. For example, a sequence including near 26 and intermediate 28 regions, near 26 and far 30 regions, intermediate 28 and far 30 regions or all three types of regions 24 can be utilized in optical zone 16. This sequence, which can be arranged in any order can be repeated at least two to at least three times. According to another preferred embodiment of the present invention. optical zone 16 includes a sequence including intermediate region 28 followed by near region 26. w hich is repeated tw ice and follow ed by a single far region 30. According to this configuration outer boundaries of regions 24 (in the order described above) are preferably positioned 1.275. 1 .525. 1 .675. 1 .9 and 4.0 mm. respectively, from lens center 20, wherein an outer boundary of region 25 is positioned 1 .125 mm from lens center 20. As is further detailed hereinbelow and in the Example which follows. focal regions 24 and central region 25 are configured with an optical power (expressed in. for example, diopters) which allows an individual fitted with a pair of lens 10 to bring into focus objects which are positioned near, far or at any distance in between away from the individual ' s eyes. It will be appreciated that the optical power of each of regions 24 and region 25 can be generated by either configuring regions 24 and region 25 from materials of a different refraction index and/or by varying the shape (degree of curvature) of front 12 and/or back 14 surfaces of each region. According to another preferred embodiment of the present invention. back surface 14 is quadrically aspherically shaped w ith substantially identical eccentricity throughout and a substantially constant radius for each of regions 24. The configuration of lens 10 according to the present invention enables an individual fitted therew ith to readily bring into focus an object located at any distance therefrom. This feature of lens 10 of the present inv ention is enabled since under certain circumstances the human brain can discriminate between separate competing images by accepting an in-focus image and rejecting an out-of-focus image. Thus, an individual fitted with lens 10 will perceive the in focus image of an object while being obliv ious to the out-of-focus images of this object. This is exempli fied by Figure 3. wherein an object 32 captured by all three types of focal regions 24. is only focused by one type of region. Thus, as shown by the three possible alternatives, only one type of focal region 24 will focus object 32 onto retina 34 (as is indicated by black image) while the other types of focal regions 24 w ill focus the same object 32 either behind or in front of the retina 34 (as indicated by gray images) and thus out of focus as perceived by the brain. Since the out-of-focus images of object 32 (as indicated by gray images in Figure 3) are disregarded by the brain, the individual perceives object 32 clearly and in focus regardless of its distance to the eye of the individual. According to another preferred embodiment of the present invention lens 10 f urther includes a tri-focal di ( Tractive microrelief profile region 40. Region 40 is positioned outside and adjacent to regions 24 of the simultaneous multifocal lens and serves for ensuring in-phase interference of regions 24 when each is at a proper focus. Lens 10 further includes a bevel region 42 and a blend region 44 interposed between edge 22 and region 40. These regions function to mechanically position lens 10 on the cornea. Thus, lens 10 of the present inv ention can be utilized for treating an individual suffering from a visual disorder, such as. for example, presbyopia, by first determining a visual acuity of an indiv idual by. for example, a common eye examination. Following the determination of the focal pow er necessary for near and far vision focal regions, by using, for example, the standard prescription for lens radius design, the focal power of the peripheral near vision focal regions is then overcorrectcd as described above and as is further exempli fied by the Example that follows. The resulting lens 10 fabricated according to the guidelines of the present invention thus provides the indiv idual w ith a range of focused v ision while substantially improving the near v ision acuity as compared to prior art lenses. Additional objects, advantages, and novel features of the present invention will become apparent to one ordinarily skilled in the art upon examination of the following example, w hich is not intended to be limiting. Additionally, each of the various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below finds experimental support in the follow ing example. EXAM PLE Reference is now made to the follow ing example, w hich together with the abov e descriptions, illustrate the invention in a non limiting fashion. The focal property of the various focal regions of the lens of the present invention is achieved by changing the radius of curvature of the various regions at one or both of the smooth optical surfaces (back and front ). For example, the back surface can feature piecewise smooth optical regions and periphery. The surface is then considered piecewise smooth instead of a fully smooth surface. This surface includes three foci regions or three types of objects distances: far. intermediate and near. The contact lens according to the present invention is designed with consideration to the following parameters: D far - optical power for far vision in accordance to prescription of the patient. Add - addition in optical power for near vision, as is compared with far vision. Rι„ ecc - radius of curvature and eccentricity ϊ base curve in accordance with the prescription of the patient {ecc - 0 corresponds to spherical shape). n - refractiv e index of the contact lens material when hydrated. CT - central thickness is determined from mechanical properties and therefore considered as a giv en for optical design. Several formulas can be utilized to calculate the optical power of a lens: (i) the "lens-maker's formula": which can be utilized for calculating the optical power (in diopters) according to the radii of curvature, (ii) the paraxial thick lens formula: and (iii) aspherical surface optimized for best focus. An inversed "lens-maker's formula" can also utilized for calculating the proper radii of curvature. The lens design according to the present invention, starts by calculating a front curve radius of curvature /? / using the following: The radius of curvature of a piecewise base curve in the regions responsible for far vision is calculated as follows: ?.,.., = R„ (4) The radius of curvature of a piecewise base curve in the regions responsible for intermediate vision is calculated as follows: R hn tk- (5) by util izing hal f of the Add correction. The radius of curvature of the piecewise base curve in the regions responsible for near v ision is expected to be as follows: Add R hu (6) /?,. 1000 (//„ - !) by using a full Add correction. The unique feature of the lens of the present invention is the use of over-correction for calculating a radius of a curvature piecew ise base curve in the regions responsible for near vision. This is effected as follows: Add ιι ι = Add - Cov ( 7) where Cov is the correction coefficient w hich is preferably selected between 1 . 1 and 1 .5. By replacing Add by Add vrr in equation 7 the follow ing equation is generated: Over-correction is utilized by the present invention only for calculating the radius of curvature of a piecewise base curve in the regions responsible for near vision, while a non-corrected (standard) Add is used for intermediate vision region(s). The use of over-correction improv es the ability of the lens according to the present invention in terms of supporting triple-foci operations, since it directs rays of light into a proper foci. As mentioned hereinabove. the lens according to the present invention, includes a back surface shaped with quadrics aspherics with the same eccentricity in all clear aperture and constant radius in each of the peripheral ring-shaped optical regions. The central region of the configuration according to the present invention is a far vision region which is surrounded by a twice repeated periodic sequence containing consecutive intermediate and near vision regions followed bv a far vision region. Thus, the lens contains six reeions w ith coordinates of borders of 1 .125 mm, 1 .275 mm. 1 .525 mm. 1 .675 mm. 1 .9 mm and 4.0 mm from the center of the lens. In addition, the lens also includes a tri-focal di ffractive microrelief profile region positioned outside the above mentioned optical regions. This tri-focal diffractive microrelief profile region ensures in-phase interference of all the optical regions when at proper focus. By fabricating the lens of the present invention w hile utilizing an Rh of 8.4. material of ιι.\f w hich equals 1 .44 and an Add alue of 2.5 the follo ing is obtained: Rbmui ie = 8*605 mm Rbn ai = 8.956 mm Thus, the optimized coordinates (semi-diameters) of the various regions are: Figures 4-6 illustrate some of the parameters of a lens fabricated according to the teachings of the present invention. Figure 4 illustrates the coordinates of the v arious optical regions and optical power distribution thereof; Figure 5 illustrates a sag difference between smooth and piecewise smooth curv e in all of the various optical regions, while Figure 6 illustrates a magnified view of the sag difference between a smooth and a piecewise smooth curve in all of the various optical regions. The design of the contact lens according to the present invention is effected via a computer simulation of retinal intensity. Figure 7 illustrates an equivalent light diffraction scheme for the various focal regions of the multifocal contact lens designed according to the present invention. Indicated are the positions of the three foci, their spot-sizes and also the light beam power distribution between foci. The peak intensity for each focus region is determined by the computer simulation. Figure 8 presents a Detailed scheme for diffraction on curved surface, while Figure 9 illustrates the tilt of the element of a curved surface. The computer simulation is based upon the following algorithm: A Cartesian 3-D coordinate system centered at the vertex ( ) of surface Λ with z-axis along optical axis is used, u = ( //, v ) is the transverse Cartesian coordinates of a current point ( u. //) on surface A . while z = //( u) is the equation for surface Λ . n kι h is the Refractive index of the media follow ing determination of surface Λ . Φ( u ) is the Phase function of a piecewise phase delay on surface Λ . Working under the assumption that a light field is concentrated around some center of observation w ith coordinates ( x ./ ) . the task is to calculate light field ir not only exactly at point (x ( ,/) but also for points ( x.l + Δz) being close thereby (see Figure 8). By using a general Kirchhoff integral, which is applicable here due to rather wide optic regions, the following can be calculated: »r( x./ + Δ_-) = K(u. x ι . Δ--) ./Λ (9) where IΓ is the light field impinging on the curved surface. L is the distance from a point on surface Λ to the impinging point. (ιι. x ( . Δr) = 0.5 [ NN + N , N is the tilt factor. </- II I S c c i \ the element of square on surface Λ (see Figure 9), V j is the gradient with respect to coordinated (u.v), N s is the unit normal vector of surface A . N is the ray unit vector after diffractive microrelief. N , is the unit vector pointing towards the observation center from the point on surface Λ . k = 2π I λ. λ - is the wavelength. In such general form. Kirchhoff integral looks rather complicated and thus cannot be utilized in a Fourier transform as is usually done for Fresnel's transform under paraxial approximation. However, in addition to the parameters describing the complexity of a non-paraxial curved surface there exist a small but useful parameter which describes the image size of the point source. Once the optical system (lens) is imaging, the spot size is small compared to the focal length - "a small-spot approximation " . Following a series of transformations with a small-spot approximation for light diffraction on microrelief located on curved radial symmetrical substrate and substitution of variables, the Kirchhoff integral can be utilized in a single Fourier transform. The substitution is nonlinear, because the distances depend on u: the intensity eikonal. and phase function can be any nonsymmetrical function. The calculation is as follows: L + (//') /V(u.O.Δr)- exp[- v I exp[/2/τ v x]<7 : v Ll„ /„ +# ■ // 2 ιΛ/ (u.Δr) (10) wherein. E h is the total power of illuminating spherical beam converging into the center x ( of watching points. S h is the square of the sphere with radius / within the optical aperture of base surface. L = V[/-//(u] : +(x , -u) : . t , = 7(/ + A_--//(u)) +(x c -u) . /„ =1- II + Δz (11) The spatial frequencies and coordinates can be represented as follows: ■ v = v . r = u (12) λ L λ + r whereas the equivalent focus is: and the tilt factor is: wherein // ' is the derivativ e of // w ith respect to r. Equation ( 10) enabled computer simulation in the case of a curved nonparaxial surface of a contact lens. All the algorithms were implemented by dedicated programs written by the inventors in C++ object-oriented programming language. The results of the computer simulation enabled optimization of the curvature radii. Hie di ffractive microrelief region of the lens of the present invention can be generated by diamond latching the region outside the optical region. For example a - 1 diffraction order with negative power is suitable for far objects, a 0 order with zero optical power is suitable for objects of an intermediate distance and a H order with positive optical power is suitable for near objects. A lens fabricated with this diffractive microrelief pattern is of an improved function because it optimally directs rays of light into the proper foci. Since multifocal contact lenses are typically fabricated from rigid or soft-ty pe plastic materials by single-path diamond-turning a software program implementing the teachings of the present invention can generate CNC or similar format files suitable for diamond tip fabrication by Rank Pneumo. Precitech and other lathes. 20 Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations w ill be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall " s within the spirit and broad scope of the appended claims. All publications cited herein are incorporated by reference in their entirety. Citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

Claims: WHAT IS CLAIMED IS: 1 . A simultaneous multifocal contact lens for correcting vision acuity of an individual, the contact lens comprising a central region radially surrounded by at least one far ision focal region and at least one near vision focal region, w herein a near v ision additional correction of said at least one near v ision focal region is overcorrectcd by at least 10 % w ith respect to said near v ision additional correction prescribed for the indiv idual according to a standard prescription for lens radius design. 2. The simultaneous multifocal contact lens of claim 1. wherein said near v ision additional correction of said at least one near vision focal region is overcorrectcd by 10 to 100 % with respect to said near vision additional correction prescribed for the individual according to the standard prescription for lens radius design. 3. The simultaneous multifocal contact lens of claim 1 , wherein said near v ision additional correction of said at least one near vision focal region is overcorrectcd by 1 5 to 70 % with respect to said near vision additional correction prescribed for the individual according to the standard prescription for lens radius design. 4. The simultaneous multi focal contact lens of claim 1 , wherein said near vision additional correction of said at least one near vision focal region is overcorrectcd by 20 to 50 % with respect to said near vision additional correction prescribed for the individual according to the standard prescription for lens radius design. 5. The simultaneous multifocal contact lens of claim 1. wherein a surface of the simultaneous multifocal contact lens which lies adjacent to a cornea of the individual is quadrically aspherically shaped with substantially identical eccentricitv throughout and a substantially constant radius for each of said at least one near and said at least one far vision focal regions. 6. The simultaneous multifocal contact lens of claim 1 . wherein aid at least one near and said at least one far vision focal regions are each shaped as distinct rings. 7. The simultaneous multi focal contact lens of claim 6, wherein said focal regions radiate outwardly from said central region in an alternating sequence including said far v ision focal region and said near v ision focal region. 8. The simultaneous multifocal lens of claim 7. wherein said sequence is repeated at least twice. 9. The simultaneous multi focal lens of claim 7. wherein said sequence is repeated at least three times. 10. The simultaneous multifocal lens of claim 9, wherein said focal regions radiating outwardly from said central region are positioned 1.125. 1 .275. 1 .525. 1 .675. 1 .9 and 4.0 mm from a center of said central region. 1 1 . The simultaneous multifocal lens of claim 1. further comprising a tri-focal diffractive microrelief profile region being positioned at an outermost region of the simultaneous multifocal lens and being for ensuring in-phase interference of said at least one near vision focal region and said at least one far v ision focal region when each being at a proper focus. 12. The simultaneous multifocal contact lens of claim 1. further comprising at least one intermediate vision focal region radially surrounding said central region. 13. The simultaneous multifocal contact lens of claim 12. wherein a surface ot the simultaneous multi focal contact lens which lies adjacent to a cornea of the indiv idual is quadi icallv asphericallv shaped w ith substantiallv identical eccentricity thioughout and a substantially constant l adius foi each of said at least one neai said at least one intermediate and said at least one lai ision focal l egions 14 The simultaneous multifocal contact lens ot claim 1 2. whci ein said at least one neat , said at least one intei mediate and said at least one far v ision focal regions ate each shaped as distinct rings 15 Hie simultaneous multifocal contact lens of claim 14 wherein said focal regions radiate outwardlv horn said central legion in an alternating sequence including said far v ision local icgion said mtei mediute v ision local legion and said neai v ision local icgion 16 The simultaneous multi local lens of claim 1 5. wherein said sequence is repeated at least twice 1 7 I he simultaneous multi focal lens of claim I s. wheiein said sequence is icpeatcd at least thiee times 1 8 The simultaneous multifocal lens of claim 14 w herem said near and intermediate focal regions radiate outwardly f rom said central region in an alternating sequence 19 The simultaneous multifocal lens of claim 1 8, wherein said sequence is repeated at least twice 20 The simultaneous multifocal lens of claim 18, wherein said sequences are surrounded bv said at least one far vision local legion 21 The simultaneous multifocal lens of claim 20. wherein said focal regions radiating outwardly from said central region are positioned 1 .275. 1 .525. 1 .675. 1 .9 and 4.0 mm from a center of said central region. 22. The simultaneous multifocal lens of claim 14, further comprising a tri-focal diffractive microrelief profile region being positioned at an outermost region of the simultaneous multifocal lens and being for ensuring in-phase interference of said at least one near vision focal region, said at least one intermediate vision focal region and said at least one far v ision focal region when each being at a proper focus. 23. The simultaneous multi focal lens of claim 1 , wherein said central region is a far vision focal region. 24. The simultaneous multifocal lens of claim 1 , w herein said central region is a near vision focal region. 25. The simultaneous multifocal lens of claim 24, wherein said near vision additional correction of said central region is as prescribed for the individual according to the standard prescription for lens radius design. 26. A method of improving v isual acuity in an indiv idual suffering from presbyopia, the method comprising the steps of: (a) fabricating, according to a prescription of the individual, a pair of simultaneous multifocal contact lenses each including a central region radially surrounded by at least one far vision focal region and at least one near vision focal region, wherein a near vision additional correction of said at least one near vision focal region is overcorrected by at least 10 % with respect to said near vision additional correction prescribed for the individual according to the standard prescription for lens radius design. (b) fitting the individual with said pair of simultaneous multifocal contact lenses to thereby improve the visual acuity of the individual. 27. The method of claim 26. w hciein said near vision additional correction of said at least one near vision focal region is overcorrectcd by 10 to 1 00 % with respect to said near v ision additional correction prescribed for the individual according to the standard prescription for lens radius design. 28. The method of claim 26. w herein said near v ision additional correction of said at least one near vision focal region is overcorrectcd by 1 5 to 70 % with respect to said near vision additional correction prescribed for the individual according to the standard prescription for lens radius design. 29. The method of claim 26. w herein said near vision additional correction of said at least one near vision focal region is overcorrected by 20 to 50 % with respect to said near vision additional correction prescribed for the individual according to the standard prescription for lens radius design. 30. The method of claim 26. wherein a surface of each of said pair of simultaneous multifocal contact lenses which lies adjacent to a cornea of the indiv idual is quadrically aspherically shaped with substantially identical eccentricity throughout and a substantially constant radius for each of said at least one near and said at least one far vision focal regions. 3 1 . The method of claim 26. wherein said at least one near and said at least one far vision focal regions are each shaped as distinct rings. 32. The method of claim 3 1. wherein said focal regions radiate outwardly from said central region in an alternating sequence including said far vision focal region and said near vision focal region. 33. The method of claim 32. wherein said sequence is repeated at least twice. 34. The method of claim 32. w herein said sequence is repeated at least three times. 35. The method of claim 34, wherein said focal regions radiating outwardly from said central region are positioned 1 . 125. 1 .275. 1 .525. 1 .675. 1 .9 and 4.0 mm from a center of said central region. 36. The method of claim 26. w herein each of said pair of simultaneous multi focal contact lenses further includes a tri-focal di ffractive microrelief profile region being positioned at an outermost region thereof and being for ensuring in-phase interference of said at least one near vision focal region and said at least one far vision focal region when each being at a proper focus. 37. The method of claim 26, wherein each of said pair of simultaneous multifocal contact lenses f urther includes at least one intermediate vision focal region radially surrounding said central region. 38. The method of claim 37. wherein a surface of each of said pair of simultaneous multifocal contact lenses which lies adjacent to a cornea of the indiv idual is quadi icallv asphericallv shaped with substantially identical eccentricity throughout and a substantially constant radius for each of said at least one near, said at least one intermediate and said at least one far v ision focal regions. 39. The method of claim 37. wherein said at least one near, said at least one intermediate and said at least one far vision focal regions are each shaped as distinct rings. 40. The method of claim 39. wherein said focal regions radiate outwardly from said central region in an alternating sequence including said far vision focal region, said intermediate v ision focal region and said near v ision focal region. 41. T he method of claim 40, w herein said sequence is repeated at least twice. 42. The method of claim 40. w herein said sequence is repeated at least three times. 43. The method of claim 37. wherein said near and intermediate focal regions radiate outwardly from said central region in an alternating sequence. 44. The method of claim 43. w herein said sequence is repeated at least twice. 45. The method of claim 43, w herein said sequences are surrounded by said at least one far vision focal region. 46. The method of claim 45. wherein said focal regions radiating outw ardly from said central region are positioned 1 .275. 1 .525. 1 .675. 1 .9 and 4.0 mm from a center of said central region. 47. The method of claim 37, wherein each o( said pair of simultaneous multifocal contact lenses further includes a tri-focal diffractive microrelief profile region being positioned at an outermost region of the simultaneous multifocal lens and being for ensuring in-phase interference of said at least one near vision focal region, said at least one intermediate vision focal region and said at least one far vision focal region when each being at a proper focus. 48. The method of claim 26. wherein said central region is a far vision focal region. 49. The method of claim 26, wherein said central region is a near v ision focal region. 50. The method of claim 49, wherein said near v ision additional correction of said central region is as prescribed for the individual according to the standard prescription for lens radius design. 51 . The simultaneous multi focal contact lens of claim 1 . w herein said near vision additional correction of a first near vision focal region of said at least one near vision focal region is overcorrectcd by n %. w hereas n is a number selected from a range between 10-50. and further w herein said near vision additional correction of a second near v ision focal region of said at least one near vision focal region is overcorrectcd by n ι- 10 %.

Inventors: GOLUB MICHAEL, GROSSINGER ISRAEL, GOLUB, MICHAEL, GROSSINGER, ISRAEL
Applicants: FRIEDMAN MARK M, GOLUB MICHAEL, GROSSINGER ISRAEL, HOLO OR LTD, FRIEDMAN, MARK, M., GOLUB, MICHAEL, GROSSINGER, ISRAEL, HOLO OR LTD.
Application year: 2000
Main classification: G02C7
IPC codes: G02C7