Polarization-sensitive spectral-domain optical coherence tomography using a single line scan camera

Barry Cense,Mircea Mujat,B H Park,Teresa C Chen,Johannes F De Boer

doi:10.1364/oe.15.002421

Abstract

Polarization-sensitive optical coherence tomography can be used to measure the birefringence of biological tissue such as the human retina. Previous measurements with a time-domain polarization-sensitive optical coherence tomography system revealed that the birefringence of the human retinal nerve fiber layer is not constant, but varies as a function of location around the optic nerve head. Here we present a spectral-domain polarization-sensitive optical coherence tomography system that uses a spectrometer configuration with a single line scan camera and a Wollaston prism in the detection arm. Since only one camera has to be synchronized with other components in the system, the design is simplified considerably. This system is 60 times faster than a time-domain polarization-sensitive optical coherence tomography system. Data was acquired using concentric circular scans around the optic nerve head of a young healthy volunteer and the acquisition time for 12 circular scans was reduced from 72 s to 1.2 s. The acquired data sets demonstrate variations in retinal thickness and double pass phase retardation per unit depth that were similar to data from the same volunteer taken with a time-domain polarization-sensitive system. The double pass phase retardation per unit depth of the retinal nerve fiber layer varied between 0.18 and 0.40 degrees/mum, equivalent to a birefringence of 2.2 * 10(-4) and 4.8 * 10(-4) respectively, measured at 840 nm.

Highlights

Optical coherence tomography (OCT) [1, 2] is a technique for non-invasive threedimensional imaging of turbid media, such as biological tissue
Polarization-sensitive optical coherence tomography can be used to measure the birefringence of biological tissue such as the human retina
Previous measurements with a time-domain polarization-sensitive optical coherence tomography system revealed that the birefringence of the human retinal nerve fiber layer is not constant, but varies as a function of location around the optic nerve head

Summary

Introduction

Optical coherence tomography (OCT) [1, 2] is a technique for non-invasive threedimensional imaging of turbid media, such as biological tissue. Polarization-sensitive OCT (PS-OCT) can measure the birefringence and optic axis of biological tissue [3,4,5,6,7]. Birefringence occurs in neatly oriented fibers of biological tissue, such as collagen, tooth enamel, and the retinal nerve fiber layer. In vivo time-domain ophthalmic PS-OCT measurements around the optic nerve head of up to five healthy young volunteers have shown the well known variation of the human retinal nerve fiber layer thickness, and more importantly have demonstrated a variation of the birefringence around the optic nerve head [8,9,10]. A birefringence measurement may be used to analyze microtubule density, which may lead to a better understanding of the pathophysiology of the nerve fiber layer architecture changes that occur in glaucoma (the world’s second leading cause of blindness). Since microtubules are 25 nm thin structures [12], sub-wavelength information on the microtubules could be acquired with PS-OCT, even though the axial and lateral resolutions of the technique are orders of magnitude lower

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