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Shinichi Fukuda, Yuta Ueno, Akari Fujita, Haruhiro Mori, Tetsuro Oshika; The corneal phase retardation measured by a prototype of anterior segment polarization-sensitive OCT. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4312.
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Keratoconus is a bilateral, progressive and noninflammatory disease characterized by ectatic thinning of the cornea. Polarization-sensitive optical coherence tomography (PS-OCT) can evaluate internal tissue structures of the cornea, such as collagen fibers. We previously reported phase retardation measurements for keratoconus using a laboratory prototype of PS-OCT. In this current study, we quantitatively assessed the corneal phase retardation in 3-mm diameter using a pre-commercial prototype of PS-OCT.
Forty-nine eyes of 30 normal subjects and 15 eyes of 21 patients with keratoconus were investigated by PS-OCT and conventional anterior segment OCT. Each cornea was scanned at least twice using PS-OCT. Horizontal, fast raster pattern on scanning ranges of 6 × 6 mm2 and 12 × 12 mm2 was used. The central cornea thickness was also measured by anterior segment OCT.
The 12 × 12 mm2 en face phase retardation image showed characteristic L pattern in normal corneas and this pattern was collapsed in keratoconic corneas (Figure). While in normal controls the 3-mm diameter of en face phase retardation image showed low and homogeneous birefringence, in keratoconic corneas the phase retardation increased. The phase retardation values of normal corneas and keratoconus were respectively 28.0 and 36.2 and there was significant difference between them (P < 0.05). The 3-mm diameter of en face phase retardation was negatively correlated with corneal thickness.
PS-OCT might be useful for evaluating phase retardation, which is one of the parameters that defines birefringence, in corneal tissue. Average of en face phase retardation of 3-mm diameter of cornea was increased in keratoconus patients compared with normal subjects, which suggested changes in the lamellar structure of collagen fibers.
This is a 2020 ARVO Annual Meeting abstract.
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