Repeatability of Retinal Macular Thickness Measurements in Patients with Clinically Significant Macular Edema Using Two Different Scanning Protocols of Spectralis Optical Coherence Tomography

Objective: To determine the repeatability of Spectralis optical coherence tomography (OCT) retinal thickness measurements in diabetic patients with clinically significant macular edema (CSME) using two different scanning protocols. Methods: Seventy-one eyes of 71 diabetic patients with CSME were included in the study. Coefficients of repeatability and intrasession variation coefficients were tested with 20 × 15 degree raster scans consisting of 19 or 37 high-resolution line scans (15 or 8 frames per scan, respectively) that were repeated 2 times by 1 experienced examiner. The first scan was set as the reference scan; the second scan was the follow-up scan and was performed with the use of the follow-up mode. Results: The mean and standard deviation for the central foveal subfield (CSF) using the first scanning method was 404 ± 88 μm, while it was 399 ± 86 μm using the second protocol, which was not statistically significantly different (p = 0.35, paired test). Particularly examining the CSF, the coefficient of repeatability was 1.48 (6.00 µm) and 1.49 (5.95 µm) for the 19- and the 37-B-scan acquisition, respectively, showing a nonstatistically significant difference (p < 0.001). Conclusions: Retinal thickness measurements in diabetic patients with CSME are repeatable using both scanning protocols (19 or 37 B-scans) with Spectralis OCT. The repeatability of the retinal thickness measurement does not improve by increasing the number of B-scans from 19 to 37.