Clinical significance of B-scan averaging with SD-OCT

Averaging multiple scans is a potential advantage of optical coherence tomography. The authors evaluate the qualitative benefits of B-scan averaging on the visualization of outer retinal structures. A retrospective analysis was performed on Cirrus OCT (Carl Zeiss Meditec, Dublin, CA) B-scans from 1 eye of 35 patients referred to the imaging unit who underwent three types of scan acquisitions: no averaging, 4× averaging, and 20× averaging. Masked assessment of quality was made using a qualitative scale of 0 (worst) to 3 according to the ability to identify structure, brightness, and continuity. Quality scores consistently improved with 4× averaging, but improved only slightly further with 20×. Averaging appeared to have a statistically significant beneficial effect for the assessment of the external limiting membrane and outer nuclear layer (P < .05), with no significant benefit for visualization of the retinal pigment epithelium and inner segment/outer segment junction. The benefits of oversampling or averaging B-scans for visualizing outer retinal substructures are apparent even when averaging relatively few frames. These findings may be helpful when designing acquisition protocols in clinical trials and clinical practice.