Reproducibility of nerve fiber layer thickness measurements by use of optical coherence tomography

Objective: To evaluate the reproducibility of optical coherence tomograph ( OCT) retinal nerve fiber layer (RNFL) measurements in normal and glaucomato us eyes by means of the commercially available OCT 2000 instrument (Humphre y Systems, Dublin, CA). Design: Prospective instrument validation study. Participants: One eye each from 10 normal subjects and 10 glaucoma patients . Methods: Twenty subjects underwent a total of eight scanning sessions durin g two independent visits. in each session, five circular scans centered on the optic nerve head were performed. The first two sessions were performed by two experienced technicians. Followed by a 30-minute break, a third and a fourth session was completed by the same technicians. This sequence was d uplicated on a second visit. Intrasession, intersession, intervisit, and in teroperator reproducibility of quadrant and global RNFL measurements were c alculated by use of a components of variance model. Main Outcome Measures: RNFL thickness. Results: The coefficient of variation for the mean RNFL thickness was signi ficantly smaller (P = 0.02) in normal eyes (6.9%) than in glaucoma eyes (11 .8%). The estimated root mean squared error based on the statistical model using three scans per patient was 5.8 and 8.0 mum for normal and glaucoma e yes, respectively. A components of variance model showed most of the varian ce (79%) to be due to differences between patients. Only a modest contribut ion to variability was found for session (1%), visit (5%), and operator (2% ). Conclusion: With the commercially available OCT, our results indicate that the RNFL measurements are reproducible for both normal and glaucomatous eye s. (C) 2000 by the American Academy of Ophthalmology.