Abstract:
A multifocal contact lens ( 10, 50 ) made of flexible material is able to translocate on an eye by virtue of a lower end ( 22 ) of the contact lens ( 10, 50 ) being truncated so as to provide a relatively wide surface. The lower end ( 22 ) engages with the lower eyelid of a wearer. The lower end ( 22 ) may be provided with a forwardly projecting ledge ( 52 ).

Description:
This application is a 35 U.S.C. §371 filing of International Patent Application No. PCT/AU00/01531, filed on Dec. 13, 2000. This application claims priority benefit of Australian Patent Application No. PQ4683 filed on Dec. 16, 1999 both incorporated by reference in their entirety herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a Contact Lens. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention there is provided a multifocal contact lens characterised in that the contact lens is made of flexible material, the contact lens is of a unitary construction and the contact lens is arranged to translocate on an eye, the contact lens having a front surface and a rear surface and an upper end and a lower end, wherein the lower end of the contact lens is truncated so as to provide a relatively deep end surface which is arranged to rest on a lower eyelid of the patient, the truncated lower end being provided with an integral forwardly projecting ledge having a lower surface which is also arranged to rest on the lower eyelid of the patient. 
    
    
     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; and 
     FIG. 4 is a cross section along the line B—B of FIG.  3 . 
    
    
     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 stabilises 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 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  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 customised 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. 
     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 . 
     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 stabilise 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.