Repeatability of retinal nerve fiber layer and ganglion cell complex measurements with spectral-domain optical coherence tomography in normal and glaucomatous eyes

Purpose The current study was set out to investigate the repeatability of retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) measurements in normal and glaucomatous patients using spectral-domain optical coherence tomography (OCT). Patients and methods This prospective cross-sectional study included 30 healthy and 30 glaucomatous eyes. Three OCT scans with the Nidek RS-3000 advance were performed three times for each scan protocol: optic disk map, optic disk circle, and macular map to determine the RNFL, cup-to-disk ratio, and GCC. Repeatability was assessed by calculating the intraclass correlation coefficient (ICC) and within-subject coefficient of variation. Results The ICC values for RNFL thickness measurements taken from the optic disk map were 0.44-0.86 in normal eyes and 0.33-0.93 in glaucomatous eyes, whereas those obtained from the optic disk circle were 0.76-0.96 and 0.92-0.99 in normal and glaucomatous eyes, respectively. The ICC values for the vertical and horizontal cup-to-disk ratio were 0.81 and 0.86 in normal eyes and 0.83 and 0.90 in glaucomatous eyes, respectively. The ICC values for the upper and lower hemifields were 0.79 and 0.83 in normal eyes and 0.84 and 0.96 in glaucomatous eyes, respectively. Conclusion RNFL thickness measurements obtained using Nidek RS-3000 advance spectral-domain-OCT demonstrated variable repeatability in healthy and glaucomatous eyes. Measurements obtained from the optic disk circle scan showed better repeatability than those obtained from the disk map. The GCC measurements exhibited good repeatability.