A method and apparatus are provided to map the shape or thickness of a
surface. Thickness estimates across a distance are received, and Fourier
analysis is performed to generate Fourier amplitude coefficients and
phase values for a number of frequency components. Linear discriminant
functions are used to characterize the resulting shape as normal or not.
Discriminant functions are provided that aid in the diagnosis of glaucoma
when the thickness measured is the retinal nerve fiber layer thickness.