Aspheric intraocular lens and method for making the same

Abstract

The invention relates to a novel artificial intraocular lens (IOL) and a method for improving such a lens in the field of opthalmology, with surface shape modifications that differ from perfect spherical geometries. The intraocular lens takes into account the natural optical configuration of the human vision apparatus, for example, visual axis tilt and pupil decentration. In addition, the method accounts for potential positioning errors caused by implantation and surgery effects.

1 . A method for designing an intraocular lens capable of adjusting the aberrations of the eye in order to provide optimal vision correction to patients, the method comprising the steps of:
 providing a mathematical model eye that describes the optical setup and performance of the natural human eye including at least one aspherical corneal surface; a gradient index and/or aspherical crystalline lens model; a visual axis that is tilted with respect to the axis of symmetry of the eye; and, a decentered iris that represents a decentered entrance pupil;   determining the performances of the mathematical model eye with respect to image quality and spherical aberrations as a function of pupil diameter;   using a mathematical model describing the statistics of potential lens misalignments and positioning errors induced by surgery or wound healing processes;   calculating the optical performance and resulting aberrations employing said mathematical eye model convoluted with the statistical model for lens displacements; and,   optically modeling an aspherical lens shape that replaces the natural human crystalline lens in the eye that provides optical power restoration while providing optical characteristics of the human lens in order to cause the eye with the intraocular lens having aspherical shape to have the same amount of spherical aberrations and the same level of image quality than the mathematical model eye as a function of the pupil diameter.   
   
   
       2 . The method of  claim 1 , wherein the radial distribution of refractive optical power is divided in at least three functional zones that account for photopic, mesopic and scotopic vision. 
   
   
       3 . The method of  claim 1 , wherein modeling and optimization of the lens shape includes selecting the radii of base curvature of the anterior and posterior surfaces as well as the central thickness, the edge thickness and the refractive index. 
   
   
       4 . The method of  claim 1 , wherein the amount of spherical aberration of a mathematical model eye having the intraocular lens is maintained at the same level as the mathematical model eye having a human crystalline lens for pupil diameters ranging from greater 0 to 4 mm. 
   
   
       5 . The method of  claim 1 , wherein the modified lens shape is defined in terms of a linear combination of polynomials. 
   
   
       6 . The method of  claim 1 , wherein the modified lens shape is defined by the equation: 
     
       
         
           
             z 
             = 
             
               
                 
                   cr 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             Q 
                           
                           ) 
                         
                          
                         
                           c 
                           2 
                         
                          
                         
                           r 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   k 
                   2 
                 
                  
                 
                   r 
                   2 
                 
               
               + 
               
                 
                   k 
                   4 
                 
                  
                 
                   r 
                   4 
                 
               
               + 
               
                 
                   k 
                   6 
                 
                  
                 
                   r 
                   6 
                 
               
               + 
               
                 
                   k 
                   8 
                 
                  
                 
                   r 
                   8 
                 
               
             
           
         
       
     
     wherein:
 c=r curv   −1  (curvature=1/base radius of curvature) 
 r=independent variable, radius about optical axis 
 Q=conic constant 
 k n =polynomial coefficient of order n. 
 
   
   
       7 . The method of  claim 6 , wherein k 2  is 0. 
   
   
       8 . An intraocular lens capable of adjusting the aberrations of the eye in order to provide optimal vision correction to patients, the intraocular lens being produced by a method which comprises the steps of:
 providing a mathematical model eye that describes the optical setup and performance of the natural human eye including at least one aspherical corneal surface; a gradient index and/or aspherical crystalline lens model; a visual axis that is tilted with respect to the axis of symmetry of the eye; and, a decentered iris that represents a decentered entrance pupil;   determining the performances of the mathematical model eye with respect to image quality and spherical aberrations as a function of pupil diameter;   using a mathematical model describing the statistics of potential lens misalignments and positioning errors induced by surgery or wound healing processes;   calculating the optical performance and resulting aberrations employing said mathematical eye model convoluted with the statistical model for lens displacements; and,   optically modeling an aspherical lens shape that replaces the natural human crystalline lens in the eye that provides optical power restoration while providing optical characteristics of the human lens in order to cause the eye with the intraocular lens having aspherical shape to have the same amount of spherical aberrations and the same level of image quality than the mathematical model eye as a function of the pupil diameter.   
   
   
       9 . The aspheric intraocular lens of  claim 8 , wherein the lens comprises an anterior and a posterior surface, whereby at least one of the anterior and posterior surfaces is aspheric and wherein the optical properties of these surfaces account for a spherical aberration equal or close to the spherical aberration of the human eye.