Patent Publication Number: US-7909459-B2

Title: Soft multifocal contact lens

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims benefit of earlier filed patent applications. This application is a continuation of U.S. application Ser. No. 11/442,694, filed May 26, 2006, entitled “SOFT MULTIFOCAL CONTACT LENS” which is a continuation of U.S. application Ser. No. 10/836,457 filed Apr. 30, 2004, entitled “SOFT MULTIFOCAL CONTACT LENS” which is a continuation-in-part of U.S. application Ser. No. 10/149,871, filed on Jun. 13, 2002, entitled “SOFT MULTIFOCAL CONTACT LENS,” which is a 35 U.S.C. §371 filing of International Patent Application No. PCT/AU00/01531, filed on Dec. 13, 2000, and entitled “SOFT MULTIFOCAL CONTACT LENS.” which further claims priority benefit of Australian Patent Application No. PQ4683 filed on Dec. 16, 1999, and entitled “SOFT MULTIFOCAL CONTACT LENS.” The entire content of all these related applications are hereby incorporated by reference in their entirety as for all purposes. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present invention relates to multifocal contact lens. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention there is provided a multifocal contact lens made of flexible material and adapted to translocate on an eye. In one example, the contact lens includes a distant vision segment and a close range vision segment; the lens having a periphery, a front surface, a rear surface having a curvature, an upper end, and a lower end. The distant vision segment is located close to the upper end relative to the close range vision segment which is located close to the lower end. A truncated portion is located at the lower end, the truncated portion being arranged to rest on a lower eyelid, and a forwardly projecting ledge is positioned at the lower end of the contact lens. The forwardly projected ledge is configured so as to project forward of a line formed by a downward extension of the curvature of an adjacent portion of the front surface. In one example, the forwardly projected ledge includes a ridge or raised strip at the lower end of the lens. 
     In another example, the contact lens includes a distant vision segment and a close range vision segment; the lens having a periphery, a front surface, a rear surface having a curvature, an upper end, and a lower end. The distant vision segment is located close to the upper end relative to the close range vision segment which is located close to the lower end. A truncated portion is located at the lower end, the truncated portion being arranged to rest on a lower eyelid. The distant vision segment and the close range vision segment meet along a substantially straight line. In one example, the line is parallel to the truncated portion when viewed from the front surface. The lens may further include a forwardly projecting ledge at the lower end of the contact lens. 
     In another example, the contact lens includes a distant vision segment and a close range vision segment; the lens having a periphery, a front surface, a rear surface having a curvature, an upper end, and a lower end. The distant vision segment is located close to the upper end relative to the close range vision segment which is located close to the lower end. A truncated portion is located at the lower end, the truncated portion being arranged to rest on a lower eyelid. The lens further including at least one secondary curve portion located at the rear surface adjacent the periphery, the at least one secondary curve portion having a curvature which is less pronounced than that of the rear surface. The secondary curve portion aids smooth translocation on a patient&#39;s eye. Additionally, the lens may further include a forwardly projecting ledge at the lower end of the contact lens. 
     In another example, the contact lens includes a distant vision segment and a close range vision segment; the lens having a periphery, a front surface, a rear surface having a curvature, an upper end, and a lower end. The distant vision segment is located close to the upper end relative to the close range vision segment which is located close to the lower end. A truncated portion is located at the lower end, the truncated portion being arranged to rest on a lower eyelid, and a forwardly projecting ledge is located at the lower end of the contact lens. The forwardly projecting ledge having a lower surface which is also arranged to rest on the lower eyelid of the user. 
     The present invention and its various embodiments are better understood upon consideration of the detailed description below in conjunction with the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a front perspective view of a contact lens in accordance with a first embodiment of the present invention; 
         FIG. 2  is a cross-section along the line A-A of  FIG. 1 ; 
         FIG. 3  is a front perspective view of a contact lens in accordance with a second embodiment of the present invention; 
         FIG. 4  is a cross-section along the line B-B of  FIG. 3 ; 
         FIGS. 5A-5C  illustrate cross-sectional views of exemplary contact lens having secondary curve portions; and 
         FIGS. 6A-6C  illustrate cross-sectional views of exemplary contact lens having secondary curve portions. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIGS. 1 and 2  of the drawings there is shown a contact lens  10  having a front surface  12  and a rear surface  14 . 
     As shown in the drawings, the front surface  12  is subdivided into a distant vision front segment  16  and a close range vision front segment  18 . 
     A distant vision front segment  16  has a curvature which preferably conforms to a spherical, aspherical or toroidal shape. It has been found that use of an aspherical shape for the front segment  16  enables the lens  10  to be made relatively thin. 
     Similarly, the close range vision front segment  18  has a curvature which preferably conforms to a spherical, aspherical or toroidal shape. It has been found that the use of an aspherical shape allows for a progressively variable close range reading area. 
     The segments  16  and  18  may meet along a laterally expanding line  20  as shown in  FIG. 1  depending on the respective curvatures of the segments  16  and  18 . Alternatively, the segments  16  and  18  may meet at a point. 
     The segment  18 , as can be seen in  FIG. 2 , may be relatively thick compared to the segment  16  and may be in the form of a prism. 
     The prism stabilizes the contact lens  10  on the eye and the amount of the prism depends on the lens power but it is preferably sufficient to hold the lens in position on the eye without rotation and without being uncomfortable for the patient. 
     The contact lens  10  is formed of a flexible material which is also soft. For example the contact lens  10  may be formed of soft hydrogel, silicone or a hybrid material formed from soft hydrogel and silicone or other flexible, non-rigid material. Further, the lens  10  is relatively large being, for example, larger than a corneal lens. 
     The contact lens  10  has a lower end  22  and an upper end  24 . The prism is located adjacent the lower end  22 . The presence of the prism adjacent the lower end  22  results in the contact lens  10  having a relatively bulky and heavy portion adjacent to the end  22 . The end  22  is, as can best be seen in  FIG. 2 , truncated so as to leave an end surface which is relatively deep as shown in  FIG. 2 , compared to a nontruncated end. The truncation of the end  22  allows the contact lens  10  to rest on a lower eye lid of a patient so as to engage and hold the contact lens  10  in position. 
     Further, the rear surface  14  of the lens  10  is formed in a curved shape which may be spherical or aspherical or may be toroidal to correct for a patient&#39;s astigmatism. Further, adjacent the end  22  and the end  24  the rear surface  14  is preferably formed with secondary curve portions  26  or  28  respectively. The secondary curve portions  26  and  28  have a curvature which is less pronounced than that of the rear surface  14  so as to modify the lens fitting on the eye so as to facilitate translocation. The secondary curves may each be a single curve, a series of curves, an aspherical curve, or a combination of these curves. 
     The secondary curve portions  26  and  28  are less pronounced (i.e., flatter) than the curvature of the main rear surface  14  of lens  10 . In various examples, the secondary curve portions  26  and  28  may include one or more of flatter curves, varying widths, varying curves, a series of blended flatter curves, aspheric, or some other design that gradually makes the peripheral secondary curve portions  26  and  28  of lesser curvature (flatter) than the curvature of rear surface  14 . The flatter peripheral curve enables lens  10  to more readily move (translate) over the flatter scleral portion of the eye when the eye looks down and the lens translates on the eye as described below. 
     In one example, a translating bifocal lens is provided with a peripheral curvature of sufficient flatness and width to allow for the lens to easily move (i.e., translate) up when the patient looks down and the lower eyelid engages the lower portion of the lens. An exemplary soft lens is shown in  FIGS. 5A and 5B , and includes a peripheral curve portion  28   a  that is approximately 0.5 mm wide and 1.00 mm flatter in radius than the base curvature of rear surface  14  of the lens.  FIGS. 6A and 6B  illustrate another exemplary lens including a curve portion  28   b  having a peripheral curvature that is preferably flatter than the curvature of rear surface  14  in the range from 0.75 mm and 3.00 mm, and more preferably between 1.0 mm and 2.75 mm. The width of the peripheral curved portion  28   a  is preferably in a range from 0.5 mm to 5.0 mm, more preferably 0.75 mm to 4.0 mm, and yet more preferably 1.1 mm to 2.50 mm. As illustrated in  FIG. 6B , the sclera (the white area of the eye) generally has a curvature that is flatter than the curvature of the cornea. The flatter and wider peripheral curve of the translating bifocal lens shown in  FIGS. 6A and 6B  allows the lens to slide or translate easily upwards onto the sclera when the user looks down and the lens engages the ledge  52  as shown in greater detail in  FIG. 6C . In contrast,  FIG. 5C  illustrates the exemplary lens shown in  FIGS. 5A and 5B  having a less flat and wide peripheral curve (e.g., a curvature closer to the curvature of rear surface  14 ), which makes translation more difficult as the lens is more likely to dig into the flatter curvature of the sclera. 
     The secondary curve portions  26  and  28  may only extend along part of the periphery of the lens  10  adjacent the ends  22  or  24  or they could be lengthened to extend around most of or all of the periphery of the lens  10 . 
     The position of the junction  20  between the segments  16  and  18  may be varied as with bifocal spectacle lens, so that the position of the close range vision portion  18  may be customized to each patient. This allows the lens  10  to be fitted precisely to an eye of an individual patient. 
     As discussed above, the lower portion of the lens  10  adjacent the end  22  is bulkier and heavier than the upper portion adjacent the end  24 . This ensures that the lens  10  is orientated in the correct way in use so that the distant vision segment  16  is uppermost and the close range vision segment  18  is lowermost. 
     Additionally, a lens including an astigmatic or toroidal power correction may be incorporated on either the front surface  12  or rear surface  14  of the lens. A toroidal lens is placed in a specific axis in the lens, and the bifocal lens incorporating the toroidal power is desirably located at a precise and stable position on the eye so the corrective prescription is maintained at the desired position. The truncated end  22  (and/or forwardly projecting ledge  52  described below) is designed to position the lens, resting on the lower lid, such that the lens is in a proper position on the eye during use to enable the corrective power more effectively. 
     Further, the contact lens  10  may have lateral lenticular portions  30  adjacent sides thereof. The lenticular portions  30 , where present, are cut away portions which reduce lens bulk. 
     The contact lens  10  preferably has an overall size of from 10 to 16 mm preferably from 12.5 to 14.5 mm. The truncation at the lower end  22  may reduce the overall size of the lens by from 0.05 to 5 mm preferably by from 0.5 to 3 mm. 
     The contact lens  10  could have a third intermediate power vision segment between the segments  16  and  18 . Further, the close range vision segment  18  may include an intermediate segment which is preferably a progressively variable or graduated portion for close vision. 
     In use, the lens  10  of  FIGS. 1 and 2  is fitted to a patient&#39;s eye with the end  22  resting on the lower eyelid of the patient. Thus, when the patient looks downward, the eye moves relative to the contact lens  10  so that the visual axis is through the close, intermediate or graduated range vision segment  18 . 
     The contact lens  10  cannot move downward because of the engagement between the end  22  and the lower eyelid. Alternatively, when the patient looks up, the eye moves again relative to the contact lens  10  which is retained in place by the weight of the segment  18 , so that the visual axis is through the upper portion of the contact lens  10  corresponding to the top portion or distant vision segment  16 . 
     Thus, in operation, the contact lens  10  translocates relative to the eye so that the patient can selectively look through the lower close range vision segment  18  or the distant vision segment  16 . Translocation is aided by the presence of the secondary curve portions  26  and  28 . 
     Line  20 , illustrating the straight line demarcation between distance segments  16  and  18 , provides a bifocal lens without (or at least reduced) undesirable “image jump” when looking from the distant portion of the lens to the close range portion of the lens. In particular, there is no sudden introduction of a prismatic effect by the close range portion at the dividing line, or at least at the point where the eye crosses the dividing line, in the translation of the eye from the distant portion to the close range portion of the lens as common in bifocal lenses having curved demarcation lines. Where the demarcation between distance and close vision segments is curved, the close vision segment exerts a prismatic effect at all points within its circumference relative to the distance portion of the lens. The effect for a user is that all objects seen through the close segment appear to have “jumped” to a new position when transitioning between segments. More particularly, with curved bifocals, the position of the optical centers of the distance and the close range portions of the lens is dependant on the powers of the lens and are always displaced. As the direction of gaze is lowered, the eye meets a gradually increasing prismatic effect as the line of vision moves away from the distance optical center. Just after it crosses the dividing line into the close range portion it suddenly meets the base down effect exerted by the close range segment. The effect on the wearer is that all the objects seen through the segment appear to have jumped to a new position. An obvious effect of the ‘jump’ is the loss in visual field. The magnitude of the jump depends, at least in part, on the distance between the optical centers of the distance and the close range portions of the lens, which is dependant on the powers of the distance and the close range portions of the lens. 
     The exemplary configurations described herein, including a straight line  20  between segments  16  and  18 , may allow a user&#39;s clarity of vision, when looking from the distance to the reading portion of the lens, to be clear and with reduced distortion or blurred vision caused by the different segments. In one example, line  20  is a substantially straight horizontal line along the curvature of the front surface  12 , e.g., parallel to lower end  22 , when viewed from the major front surface of lens  10 . The optical center of a lens is the only point in the lens where there is no prismatic effect. With the straight line bifocal design, the optical centers at least closely coincide resulting in elimination of the image jump (or at least reduced image jump relative to curved demarcation lenses) as the eye moves from the distance portion to the close range portion of the lens. In one example, a bifocal lens includes a straight line dividing the distance and the close range portions of the lens having a virtual superimposition of the optic centers of both the distance and the close range portions on the dividing line. 
     In  FIGS. 3 and 4 , there is shown a contact lens  50  which is similar to the contact lens  10  and like reference numerals denote like parts. 
     In this case, however, the lower end  22  is provided with an integral forwardly projecting ledge  52  which, in use, is arranged to rest on the lower eyelid. The use of the ledge  52  has the advantage that the segment  18  may be made thinner than in the contact lens  10 . Alternatively, the ledge  52  may be used in conjunction with a prism to add bulk to the lower part of the contact lens  50  to assist in correct lens orientation. 
     Further, the use of a thinner segment  18  reduces the overall weight of the contact lens  50 . Thus, the contact lens  50  may or may not have the lenticular portions  30  of the contact lens  10 . 
     The ledge  52  may extend across the entire lower end  22  of the lens  50  or over only a portion of the lower end  22 . Typically, the ledge  52  may be from 2 to 10 mm, preferably from 4 to 6 mm wide at the end  22  where the contact lens  50  is truncated. 
     The presence of the ledge  52  adds bulk to the lower end  22  so allowing good lid action on the contact lens  50  to allow for lens translocation. 
     Further, as can be seen in  FIG. 3 , the ledge  52  may be provided with upwardly curved end portions  54  which act as weights and help to stabilize the contact lens  50  in use. The ledge  52  and the portions  54  may be conveniently formed by means of a lather or incorporated in a mould depending on the method of manufacture. Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. 
     Additionally, in one example, ledge  52  may be configured to project forward of a line formed by a downward extension of curvature of an adjacent portion of the front surface  12 , for example, extending forward of the curvature of the lower, close range portion  18 . The forwardly projecting ledge  52  thereby forms a ridge or elevated portion extending out from the adjacent surface, which is configured to assist in abutting a patient&#39;s eyelid and thereby aid in translocation of the lens on the eye. In one example, ledge  52  includes a raised strip formed along a portion of close range portion  18  and adjacent the lower end  22 . 
     The above detailed description is provided to illustrate exemplary embodiments and is not intended to be limiting. It will be apparent to those of ordinary skill in the art that numerous modification and variations within the scope of the present invention are possible. Further, various combinations of different examples may be used alone or in combination. Additionally, particular examples have been discussed and how these examples are thought to be advantageous or address certain disadvantages in related art. This discussion is not meant, however, to restrict the various examples to methods and/or systems that actually address or solve the disadvantages.