Purpose: The detection of changes in the retinal nerve fiber layer (RNFL) as measured by optical coherence tomography (OCT) is crucial in glaucoma diagnosis and management. We investigated the short-term repeatability of peripapillary RNFL measurements in a commercially available spectral domain OCT focusing on a broad clinical spectrum of patients.
Methods: Two consecutive peripapillary RNFL measurements were taken on 227 eyes with Cirrus HD-OCT (Carl Zeiss Meditec, Version 6.5 software) using the optic disc 200 × 200 protocol. Repeatability was assessed as Bland-Altman limits of agreement and intraclass coefficients (ICCs).
Results: Limits of agreement showed the greatest variability in the superior RNFL quadrant at ±7.5 μm and the least variability in the temporal quadrant at ±5.2 μm. The short-term repeatability for the average RNFL thickness resulted in an ICC of 0.98 and variability of 3.81 μm. Individual quadrants were similar, excepting the nasal RNFL quadrant with an ICC of 0.94. Inferior and temporal quadrants were the most repeatable with a variability of 2 to 3% instrument error.
Conclusions: Cirrus HD-OCT has excellent short-term repeatability for peripapillary RNFL measurements in a mixed patient cohort. Retinal nerve fiber layer measurements are less reliable in the nasal RNFL quadrant. As other quadrants are used in glaucoma diagnosis, the detection of glaucomatous progression would be reliable.