■ BACKGROUND AND OBJECTIVE: To evaluate the repeatability of optic nerve head (ONH) measurements by spectral-domain optical coherence tomography. ■ PATIENTS AND METHODS: Three scans were acquired in 32 healthy subjects during one session. Using Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA), the cup-to-disc ratio (CDR), disc area, rim area, cup volume, and horizontal and vertical CDRs were investigated. Repeatability was assessed by the coefficient of variation (COV), the test - retest intrasession variability, and the intraclass correlation coefficient (ICC). ■ RESULTS: Good repeatability was achieved for all parameters, with a COV of 4.23% or less and ICCs of 0.98 or greater for all measurements. Test - retest intrasession variability was 0.024 for CDR, 0.121 mm2 for disc area, 0.087 mm2 for rim area, 0.017 mm3 for cup volume, and 0.048 for horizontal and vertical CDR. ■ CONCLUSION: In healthy eyes, Cirrus HD-OCT provides repeatable measurements of ONH parameters.
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