Retinal imaging with polarization-sensitive optical coherence tomography and adaptive optics

Barry Cense,Weihua Gao,Jeffrey M Brown,Mircea Mujat,Ravi S Jonnal,Steven M Jones,Johannes F De Boer,B Hyle Park,Donald T Miller

doi:10.1364/oe.17.021634

Abstract

Various layers of the retina are well known to alter the polarization state of light. Such changes in polarization may be a sensitive indicator of tissue structure and function, and as such have gained increased clinical attention. Here we demonstrate a polarization-sensitive optical coherence tomography (PS-OCT) system that incorporates adaptive optics (AO) in the sample arm and a single line scan camera in the detection arm. We quantify the benefit of AO for PS-OCT in terms of signal-to-noise, lateral resolution, and speckle size. Double pass phase retardation per unit depth values ranging from 0.25 degrees/microm to 0.65 degrees/microm were found in the birefringent nerve fiber layer at 6 degrees eccentricity, superior to the fovea, with the highest values being noticeably higher than previously reported with PS-OCT around the optic nerve head. Moreover, fast axis orientation and degree of polarization uniformity measurements made with AO-PS-OCT demonstrate polarization scrambling in the retinal pigment epithelium at the highest resolution reported to date.

Highlights

Glaucoma causes irreversible damage to the retinal ganglion cells and its axons [1]
Fast axis orientation and degree of polarization uniformity measurements made with adaptive optics (AO)-polarization-sensitive optical coherence tomography (PS-optical coherence tomography (OCT)) demonstrate polarization scrambling in the retinal pigment epithelium at the highest resolution reported to date
These axons disappear during glaucoma progression, causing a characteristic retinal nerve fiber layer thinning at the retinal poles, which can be diagnosed and monitored with retinal imaging systems such as scanning laser ophthalmoscopy (SLO), scanning laser polarimetry (SLP) and optical coherence tomography (OCT)

Summary

Introduction

Glaucoma causes irreversible damage to the retinal ganglion cells and its axons [1]. Axons of the ganglion cells aggregate in arcuate bundles at the inferior and superior poles of the optic nerve head. Intensity-based imaging with SD-OCT has proven highly successful, yet its effectiveness for detecting early-stage glaucoma is challenged by the subtle thickness changes and compositional changes of the retinal nerve fiber layer that accompany the disease. The latter is evident even in healthy eyes in which the glial content of nerve fiber bundles is known to vary significantly (18% to 42% of the cross sectional area in primates) [7]. Such variation cannot be distinguished with intensity-based SD-OCT

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