US 11,751,764 B2
Measuring a posterior corneal surface of an eye
Daniil Nekrassov, Berlin (DE); and Martin Gruendig, Rangsdorf (DE)
Assigned to Alcon Inc., Fribourg (CH)
Filed by ALCON INC., Fribourg (CH)
Filed on May 8, 2019, as Appl. No. 16/406,828.
Claims priority of provisional application 62/675,429, filed on May 23, 2018.
Prior Publication US 2019/0357767 A1, Nov. 28, 2019
Int. Cl. A61B 3/107 (2006.01); A61B 3/103 (2006.01); A61B 3/14 (2006.01); A61B 3/00 (2006.01); G06T 7/00 (2017.01); H04N 7/18 (2006.01)
CPC A61B 3/107 (2013.01) [A61B 3/0025 (2013.01); A61B 3/14 (2013.01); G06T 7/0016 (2013.01); H04N 7/181 (2013.01); G06T 2207/30041 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A system for measuring a posterior corneal surface of a cornea of an eye, comprising:
a plurality of cameras, each camera configured to generate image data representing a part of the eye posterior to the cornea, the part comprising an iris of the eye, the image data describing locations of a plurality of iris features of the iris, the locations on the iris features serving as landmarks used to align images from each of the plurality of cameras; and
a computer comprising:
a memory configured to:
store the image data from the cameras;
store a description of the shape of an anterior corneal surface of the cornea; and
one or more processors configured to apply a ray-tracing process to determine the shape of the posterior corneal surface, the ray-tracing process comprising:
define a plurality of rays, each ray traced from a camera of the plurality of cameras, through the anterior corneal surface and the posterior corneal surface, and to the iris of the eye;
determine a plurality of constraints for the rays, the constraints calculated using the description of the shape of the anterior corneal surface and locations of the iris features of the iris in the image data, the constraints calculated by:
for each ray, calculating a posterior point where the ray intersects with the posterior corneal surface according to a position of the ray subsequent to the refraction by the anterior corneal surface;
assuming a shape of the posterior corneal surface according to the posterior points calculated according to the positions of the rays subsequent to the refraction by the anterior corneal surface; and
for each ray, calculating a posterior angle by which the posterior corneal surface refracts the ray towards the iris according to the assumed shape of the posterior corneal surface at the posterior point where the ray intersects the posterior corneal surface; and
optimize a plurality of parameters according to the constraints, the optimized parameters describing the shape of the posterior corneal surface.