Duration 5min, Q&A 3min
Repeatability of Corneal Measurements with Anterior Segment Polarization-Sensitive Optical Coherence Tomography
Anterior Segment Polarization-Sensitive Optical Coherence Tomography (PS-OCT) is a new technology which can evaluate birefringence of ocular tissues. The aim of this study was to verify the repeatability of corneal measurements with PS-OCT.
Eleven normal eyes of 11 young individuals (22.9 ± 0.8 years) and 11 eyes of 7 patients with keratoconus (27.4 ± 3.4 years) were evaluated.
Subjects were measured with a custom-made three-dimensional anterior segment PS-OCT built by the Computational Optics Group of University of Tsukuba. This system uses a swept-source OCT technology with a probe wavelength of 1.3µm, and a scanning speed of 30,000 A-lines/s. Central portion of the corneas were scanned with a horizontal raster pattern on scanning ranges of 4 x 4 mm2, with each scanning range including 512 horizontal x 128 vertical A-lines. Each scan acquired tomographic volumes of a structural OCT and polarization sensitive OCT. From this scanning area, an annular area of 0.4 to 3 mm diameter was cropped, and en face phase retardation maps were obtained. For the analysis, those maps were denominated as 3 mm diameter phase retardation. Besides, in the phase retardation maps, the phase retardation was also mapped using a hue color map ranging from 0 to π. Two measurements of the same cornea were consecutively done by the same operator. Coefficient of repeatability and intraclass coefficient (ICC) for the measurements were calculated.
Results and Conclusion
The values for 3 mm diameter of en face phase retardation maps were 0.188 ± 0.197 (mean ±SD) for the first measurements, and 0.184 ± 0.216 for the second measurements recorded with the equipment. Coefficient of repeatability was 0.977, and ICC was 0.948. Measurements of normal and keratoconic corneas obtained by the same operator using PS-OCT showed good repeatability.
[ Keyword ]
Polarization-Sensitive OCT / cornea / keratoconus / repeatability
[ Conflict of Interest ]