Polarization sensitive OCT of the primate and rabbit eye

Abstract

We have successfully built and verified operation of a polarization sensitive optical coherence tomography (PSOCT) system operating at 850 nm. This system was utilized to image six rabbit eyes and two rhesus monkey eyes both in vivo and immediately ex vivo. PSOCT images of the cornea, crystalline lens, and the retina were analyzed. In all eyes, the corneas were found to be highly birefringent with considerable lateral variation in polarization. Lateral variation in corneal birefringence resulted in a corresponding change in the initial polarization state of light incident on the retina. When the corneas were removed and replaced with a non-birefringent keratoprosthesis, the initial polarization state at the retinal surface exhibited no lateral variation. This observation indicates that the crystalline lens contributes little, if any, to the birefringence signal. In fact, measurements made on freshly excised crystalline lens showed a double pass phase retardation of only 6.5 degrees. PSOCT retinal nerve fiber layer (RNFL) thickness measurements were the same with the intact cornea and with the keratoprosthesis. The lateral variation in corneal birefringence did not affect the PSOCT RNFL measurements because the PSOCT signal measures depth resolved changes in birefringence. With the intact cornea, the change in birefringence as a function of depth was independent of the initial polarization state.