MINIMAL OPTICAL COHERENCE TOMOGRAPHY B-SCAN DENSITY FOR RELIABLE DETECTION OF INTRARETINAL AND SUBRETINAL FLUID IN MACULAR DISEASES.

PURPOSE: To determine the minimal optical coherence tomography B-scan density for reliable detection of intraretinal and subretinal fluid. METHODS: Spectral domain optical coherence tomography raster scanning (Spectralis; Heidelberg Engineering, Heidelberg, Germany) using a scan field of 20° × 20° of 97 B-scans with an interscan distance (ISD) of 60 µm was performed in 150 eyes of 150 consecutive patients at monitoring visits for intravitreal anti-vascular endothelial growth factor therapy. Using custom software, every other B-scan was repeatedly deleted to generate additional data sets with an ISD of 120 µm (49 B-scans), 240 µm (25 B-scans), and 480 µm (13 B-scans). Two independent reviewers evaluated the data sets for the presence of cystoid spaces of intraretinal fluid and subretinal fluid. RESULTS: Treatment diagnoses were neovascular age-related macular degeneration (68.0%), macular edema secondary to retinal vein occlusion (20.7%), diabetic macular edema (10.7%), and other retinal diseases (4.0%). Using the source data sets with an ISD of 60 µm, intraretinal fluid was detected in 56.0%, subretinal fluid in 19.3%, and either/both in 68.7%. Compared with these results, the sensitivity of detection of intraretinal fluid and/or subretinal fluid using an ISD of 120 µm, 240 µm, and 480 µm was 99.0% (95% confidence interval, 94.7-100.0; P = 0.5), 97.1% (91.7-99.4; P = 0.1), and 87.4% (79.4-93.1; P = 0.0001), respectively. CONCLUSION: An increase of ISD up to 240 µm does not significantly impair the detection of treatment-relevant exudative retinal changes in monitoring during intravitreal therapy of macular diseases. These findings are relevant for the choice of optical coherence tomography B-scan density in both routine clinical care and interventional clinical studies.