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Barry Cense, Qiang Wang, Jason Besecker, Sangyeol Lee, Weihua Gao, Donald T. Miller; 2D Mapping Of Phase Retardation Of Henle’s Fiber Layer Using Polarization-Sensitive Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1705.
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Macular diseases such as age-related macular degeneration and diabetic retinopathy are known to disrupt the organization of Henle’s fiber layer (HFL). Since the organization is a source of phase retardation, a decrease in retardation may be a sensitive indicator of macular disease. To date, a quantitative assessment of the phase retardation induced by HFL has not been performed. Here, we map the two-dimensional distribution of double pass phase retardation (DPPR) of HFL using polarization-sensitive OCT (PS-OCT) in normal (young (n = 10, aged 26 ± 3 years); old (n = 10, aged 57 ± 5 years)) and glaucomatous subjects (n = 5, aged 60 ± 7).
A spectral-domain PS-OCT system was constructed with a spectrometer in which a Wollaston prism separated two orthogonal polarization states on a single linescan camera. The right eye of each subject was imaged with PS-OCT without dilation. Volumetric scans of 15°x15° and centered on the fovea were recorded at an A-line acquisition rate of 25 kHz. The phase retardation induced by HFL was determined using a Stokes vector calculation. To avoid contamination by nerve fiber retardation, Stokes vectors were computed for the anterior surface of HFL and the photoreceptor cilium layer. Phase retardation induced by HFL was obtained by comparing the two sets of vectors.
Figure 1 displays DPPR maps of the 15°x15° retinal patches of a normal (left) and glaucomatous subject (right). The measurement on the normal subject demonstrates an annulus of elevated DPPR centered on the fovea, suggestive of increased numbers of photoreceptor axons (oriented radially) in the elevated region. For the glaucomatous subject, the superior half of the map reveals a significantly lower DPPR, suggestive of disruption in HFL.
PS-OCT permits mapping of the two-dimensional DPPR distribution in the macular region of both normal and glaucomatous subjects.
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