Objective: To compare the detection of clinically significant diabetic macular edema (DME) by an optical coherence tomography (OCT) grid scanning protocol and biomicroscopic examination. Design: Retrospective case series. Participants: Outpatients at the Doheny Eye Institute. Methods: The clinical and imaging records of a consecutive series of 71 eyes of 40 patients referred for DME who underwent OCT using the both the Macular Grid 5 (MG5) scanning protocol (to allow a more evenly distributed sampling of points in the macula) and the standard Fast Macular Thickness Map (FMTM) pattern were reviewed. An automated algorithm was developed to generate a retinal thickness map using the MG5 data, which was then compared with a normative database to identify presumed areas of retinal edema. Clinically significant macular edema (CSME) was also identified by clinical examination and stereoscopic fundus photographs for comparison with the results of the OCT protocols. Main Outcome Measures: Sensitivity and specificity of scanning protocols. Results: Optical coherence tomograms were inspected visually, and automatically detected retinal boundaries were found to be correct in 69 of 71 MG5 scans and in 65 of 71 FMTM scans. Macular Grid 5 scanning was performed twice in each eye, and the repeatability (pooled standard deviation) of the total area of edema was 0.48 mm2 (coefficient of variation, 6.8%). Sensitivity and specificity of the MG5 for detection of CSME relative to the clinical examination were 89% and 86%, respectively, with κ being 0.74. Macular Grid 5 and FMTM assessment of foveal CSME also showed good agreement, with κ being 0.68. Conclusions: The analysis algorithm for the OCT MG5 grid scan seems to be accurate and repeatable. Automated detection of CSME by the MG5 analysis correlated well with the clinical grading and standard OCT analysis (FMTM). Macular Grid 5 provides more information regarding the perifoveal macula than FMTM and may be of value to clinicians in planning treatment and in future studies of macular edema.
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