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Ahmed M. Hagag, Maolong Tang, Yan Li, David Huang; Scleral toricity measurement with 1050 nm Swept-Source Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4272.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the repeatability of scleral toricity measurement using swept-source optical coherence tomography (SS-OCT).
A scan pattern containing 4 evenly-spaced (at 0°, 45°, 90° and 135° meridians) radial scans (20 mm length) centered on corneal apex were obtained using an experimental 100 kHz SS-OCT system. The system operates at a 1050 nm wave length and has axial and transverse resolution of 6.2 and 22 μm, respectively. Three consecutive scans were taken for each eye. A lid speculum was put on the eye during OCT scanning. Corneal diameter, anterior chamber width, corneal sagittal height and scleral sagittal depth at 7.5 mm and 8.5 mm from corneal bisector line were measured by computer calibers after manual identification of scleral spurs and scleral sulci. Scleral toricity was calculated as the difference in average scleral sagittal height between horizontal and vertical meridians. Repeatability of SS-OCT in anterior segment measurements were evaluated by pooled standard deviation (SD) and coefficient of variation (CV).
Eleven eyes of eleven normal subjects were included. Scleral spurs were visible in all subjects in 0° and 45° meridians. However, they were only visible in 10 subjects (91%) at 135° and 4 subjects (36%) at the vertical meridian. Anterior chamber width vertically (12.28 mm) was wider than it horizontally (11.82 mm, p = 0.01). SS-OCT showed better repeatability in all measurements (Table 1), especially scleral toricity (pooled SD = 0.019 mm) compared to those previously reported by TD-OCT system (pooled SD = 0.087 mm for scleral toricity).
SS-OCT system is able to provide precise measurements of clinically useful parameters in the anterior segment of the eye. However, difficulty was encountered in acquiring wide scans of sclera in the vertical meridian in primary gaze. Measurement of corneal dimensions and scleral toricity may be helpful in the fitting of scleral contact lens.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Anterior scleral sulci were located by a perpendicular line from scleral spur to the anterior surface of the eye. Corneal diameter is the distance between the two anterior scleral sulci. Anterior chamber width is the distance between the two scleral spurs. Sagittal depth at 15 and 17 mm diameters were calculated as the average of perpendicular distance between a 15 and 17 mm chords, perpendicular to bisector line, and scleral surface on both sides.
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