Reproducibility of retinal nerve fiber layer thickness measurements using the eye tracker and the retest function of spectralis SD-OCT in glaucomatous and healthy control eyes

Purpose. To evaluate the impact of Spectralis self-acting eye-tracking (eye tracker) and retest software on the reproducibility of retinal nerve fiber layer (RNFL) thickness measurements in glaucomatous and healthy control eyes by SD-OCT. Methods. RNFL thickness was measured in 56 normal and 47 glaucomatous eyes by one operator within one session with a brief rest between measurements. Three measurements were taken with the eye tracker and the retest function engaged (method A), and three measurements were taken without the eye tracker and without the retest function (method B). Method A and B measurements were taken alternately. Results. Reliability, measured by intraclass correlation coefficient (ICC) for absolute agreement and coefficient of variation (COV), was calculated for the global mean RNFL thickness (G), for each sector and for the peripapillary bundle. The ICC (and lower 95% confidence interval [CI]) for the global mean RNFL thickness (G) for method A measurements in both normal and glaucomatous eyes was 0.99 (0.98 CI). In glaucomatous eyes, the COV for method B measurements was between 2.7% and 10.5%, and between 1.3% and 3.5% for method A measurements. Conclusions. The reproducibility of RNFL measurements with Spectralis SD-OCT is excellent in both normal and glaucomatous eyes and can be significantly improved by using the eye tracker and retest software. The gain of reproducibility by using the software is significantly higher in glaucomatous eyes than in normal eyes. These findings suggest that software applications are capable of significantly improving the reproducibility of RNFL thickness measurements. (ClinicalTrials.gov number, NCT01228721.)