Spectral Dependence of Corneal Birefringence at Visible Wavelengths

Abstract

Abstract: : Purpose: To determine the wavelength dependence of corneal birefringence. Methods: A corneal polarimeter described previously (ARVO 2001; IOVS 2002;43:82-86) was modified to incorporate a multi-spectral light source and a video detector. Corneal birefringence was measured by using a variable retarder to null the fourth Purkinje image viewed through crossed polarizers. The corneas of five eyes of five normal subjects were measured three times at each of several wavelengths from 440 to 700 nm. Results: Corneal axis did not vary significantly with wavelength. Corneal retardance ranged from 85-143 nm in the five subjects. Pooling variances across subjects, the within wavelength s.d. was 10.2 nm and the between wavelength s.d. was 5.3 nm. Conclusion: Corneal birefringence was constant across visible wavelengths. This is consistent with the frequently assumed mechanism of form birefringence, i.e., birefringence due to oriented collagen fibrils in the corneal stroma.

Keywords: 370 cornea: basic science • 500 optical properties