Adaptive confocal scanning laser polarimeter for early and accurate detection of glaucoma

Glaucoma is a leading cause of blindness in the world. It is painless and irreversible. Prevention and control of the progression depend on early diagnosis. Early symptoms include loss and thinning of optical nerve fiber, and accurate and quantitative measurement of the thickness of the optical nerve fiber layer provides an objective tool for early diagnosis. Due to the periodic structure of the optic nerve fiber, it possesses the property of form birefringence. Therefore, the thickness of the optic nerve fiber layer can be measured by the phase retardation when a polarized light is incident on to the eye and travels back from the eye. The confounding factor is that the cornea is also birefringent, and each individual has different phase retardation in the cornea. We have developed a method to measure the phase retardation of the cornea by using the intrinsic polarimeter in the Henle nerve fiber layer and then use an adaptive optical phase retarder to compensate for the retardance of the cornea. We further developed an algorithm to significantly improve the system measurement accuracy of the optical nerve fiber layer by more than an order of magnitude.