Disclosed is a system for determining one or more physical lengths of an eye. The system comprises a memory configured to store location information and one or more processors. The one or more processors are configured to determine an optical length of each segment of a plurality of segments of an axis (20) of the eye, each segment corresponding to a portion of the eye； and determine a refractive index of each segment of the plurality of segments to yield a plurality of refractive indices. The refractive index is determined by obtaining a plurality of length pairs, each pair comprising a pre-operative physical length and a post-operative physical length, each pair estimating a physical length of at least a portion of the axis (20)； and determining the plurality of refractive indices that yield the pre-operative physical length substantially equal to the post-operative physical length for each pair. The one or more processors are also configured to calculate a physical length of each segment of the plurality of segments according to the optical length and the refractive index of the segment to yield a plurality of physical lengths； and calculate an lOL power of an lOL (28) using the physical lengths to correct vision of the eye.
