Method for characterizing a cornea and obtaining an ophthalmic lens

Abstract

A system and method for determining the shape of a cornea of an eye illuminates at least one of the interior surface, the posterior surface, and the interior region of the eye with infrared light of a wavelength that can generate fluorescent light from the portion of the cornea illuminated. The generated fluorescent light is then detected. The step of illuminating can comprise focusing the infrared light in a plurality of different planes substantially perpendicular to the optical axis of the eye. From the detected light it is possible to create a map of at least a portion of the interior surface, at least a portion of the posterior surface, and/or portion of the interior region of the cornea. Clarity of vision can be determined by generating autofluorescence from proteins in the pigment epithelial cells of the retina.

I claim: 
     
         1 . A method for determining an optical adjustment for a custom IOL for a patient comprising the steps of:
 a) generating a map of a cornea of an eye of the patient by
 i) illuminating a portion of the cornea, said portion of the cornea comprising an anterior surface, a posterior surface, and an interior region between the anterior and posterior surfaces of the cornea, by scanning focused infrared light in a plurality of different planes within said portion of the cornea that are substantially perpendicular to an optical axis of the eye, said plurality of planes intersecting the following:
 a) a first portion of the anterior surface and a first portion of the interior region, 
 b) a second portion of the anterior surface, a second portion of the interior region and a first portion of the posterior surface, and 
 c) a second portion of the posterior surface and a third portion of the interior region, 
 
 wherein the infrared light is of a wavelength that generates fluorescent light and Second Harmonic Generation imaging (SHGi) signal by nonlinear optical processes from the portion of the cornea illuminated; 
 ii) detecting and evaluating the generated fluorescent light and SHGi signal generated from the portion of the cornea illuminated; 
 iii) determining the shape of the anterior and posterior surfaces and a spatially resolved thickness measurement of the portion of the cornea illuminated from the detected fluorescent light and the SHGi signal; 
 iv) determining from the SHGi signal the three dimensional layered structure of corneal stroma tissue; 
 v) deriving, using finite element modeling, optical path lengths for the portion of the cornea illuminated from the detected fluorescent light and SHGi signal; 
 vi) generating the map using the derived optical path lengths, wherein the map is of the anterior surface, posterior surface and the interior region for the portion of the cornea illuminated; and 
   b) determining a diopter power correction needed by the eye from the generated map of the cornea.   
     
     
         2 . The method of  claim 1  comprising the additional steps of:
 c) selecting a lens blank sized to serve as an IOL; and 
 d) modifying the index of refraction at a plurality of locations in the blank to yield the determined diopter power correction. 
 
     
     
         3 . The method of  claim 1  comprising the additional step of determining the aspheric correction from the generated map of the cornea. 
     
     
         4 . The method of  claim 3  comprising the additional steps of:
 c) selecting a lens blank sized to serve as an IOL; and 
 d) modifying the index of refraction at a plurality of locations in the blank to yield the determined diopter power and spherical corrections. 
 
     
     
         5 . The method of  claim 1  comprising the additional step of determining the toric correction from the generated map of the cornea. 
     
     
         6 . The method of  claim 1  comprising the additional steps of:
 c) selecting a lens blank sized to serve as an IOL; and 
 d) modifying the index of refraction at a plurality of locations in the blank to yield the determined diopter power and toric corrections. 
 
     
     
         7 . The method of  claim 1  comprising the additional steps of:
 c) selecting a lens blank sized to serve as an IOL; and 
 d) modifying the index of refraction at a plurality of locations in the blank to yield the determined diopter power, spheric, and tonic corrections. 
 
     
     
         8 . A method for determining an optical adjustment for a custom IOL for a patient comprising:
 a) generating a map of the optical path length differences of a cornea of an eye by
 i) illuminating a portion of the cornea, said portion of the cornea comprising an anterior surface, a posterior surface, and an interior region between the anterior and posterior surfaces of the cornea, by scanning focused infrared light in a plurality of different planes within said portion of the cornea that are substantially perpendicular to an optical axis of the eye, said plurality of planes intersecting the following:
 a) a first portion of the anterior surface and a first portion of the interior region, 
 b) a second portion of the anterior surface, a second portion of the interior region and a first portion of the posterior surface, and 
 c) a second portion of the posterior surface and a third portion of the interior region, 
 
 wherein the infrared light is of a wavelength that generates fluorescent light and Second Harmonic Generation imaging (SHGi) signal by nonlinear optical process from the portion of the cornea illuminated; 
 ii) detecting and evaluating the generated fluorescent light and SHGi signal generated from the portion of the cornea illuminated; 
 iii) determining the shape of the anterior and posterior surfaces and a spatially resolved thickness measurement of the portion of the cornea illuminated from the detected fluorescent light and the SHGi signal; 
 iv) determining from the SHGi signal the three dimensional layered structure of corneal stroma tissue; 
 v) deriving, using finite element modeling, optical path lengths for the portion of the cornea illuminated from the detected fluorescent light and SHGi signal; and 
 iv) generating the map of the portion of the cornea illuminated using the derived optical path lengths, wherein the map is of the spatial distribution of optical path lengths for the portion of the cornea illuminated; and 
   b) determining an optical adjustment needed by the eye from the generated map of the spatial distribution of optical path lengths.   
     
     
         9 . The method of  claim 8  comprising the additional steps of:
 c) selecting a lens blank sized to serve as the IOL; and 
 d) modifying the index of refraction at a plurality of locations in the blank to yield the determined diopter power correction. 
 
     
     
         10 . The method of  claim 8  comprising the additional step of determining the aspheric correction from the generated map of the cornea. 
     
     
         11 . The method of  claim 8  comprising the additional steps of:
 c) selecting a lens blank sized to serve as the IOL; and 
 d) modifying the index of refraction at a plurality of locations in the blank to yield the determined diopter power and spherical corrections. 
 
     
     
         12 . The method of  claim 8  comprising the additional step of determining the toric correction from the generated map of the cornea. 
     
     
         13 . The method of  claim 8  comprising the additional steps of:
 c) selecting a lens blank sized to serve as the IOL; and 
 d) modifying the index of refraction at a plurality of locations in the blank to yield the determined diopter power and toric corrections. 
 
     
     
         14 . The method of  claim 8  comprising the additional steps of:
 c) selecting a lens blank sized to serve as an IOL; and 
 d) modifying the index of refraction at a plurality of locations in the blank to yield the determined diopter power, spheric and toric corrections.