Impact of scanning density on measurements from spectral domain optical coherence tomography.

PURPOSE To investigate the relationship between B-scan density and retinal thickness measurements obtained by spectral domain optical coherence tomography (SDOCT) in eyes with retinal disease. METHODS Data were collected from 115 patients who underwent volume OCT imaging with Cirrus HD-OCT using the 512 x 128 horizontal raster protocol. Raw OCT data, including the location of the automated retinal boundaries, were exported from the Cirrus HD-OCT instrument and imported into the Doheny Image Reading Center (DIRC) OCT viewing and grading software, termed "3D-OCTOR." For each case, retinal thickness maps similar to those produced by Cirrus HD-OCT were generated using all 128 B-scans, as well as using less dense subsets of scans, ranging from every other scan to every 16th scan. Retinal thickness measurements derived using only a subset of scans were compared to measurements using all 128 B-scans, and differences for the foveal central subfield (FCS) and total macular volume were computed. RESULTS The mean error in FCS retinal thickness measurement increased as the density of B-scans decreased, but the error was small (<2 microm), except at the sparsest densities evaluated. The maximum error at a density of every fourth scan (32 scans spaced 188 microm apart) was <1%. CONCLUSIONS B-scan density in volume SDOCT acquisitions can be reduced to 32 horizontal B-scans (spaced 188 microm apart) with minimal change in calculated retinal thickness measurements. This information may be of value in design of scanning protocols for SDOCT for use in future clinical trials.