Detection of diabetic foveal edema - Contact lens biomicroscopy compared with optical coherence tomography

Objective: To compare contact lens biomicroscopy with optical coherence tomography (OCT) for the detection of diabetic foveal edema. Methods: Study participants consisted of a convenient cohort of consecutive patients with diabetes mellitus seen at the Wilmer Eye Institute's Retinal Vascular Center, Baltimore, Md. Case characteristics were recorded and eyes were examined by I of 4 retina specialists by means of contact lens biomicroscopy. Edema involving the center of the macula was assessed as definitely present, questionably present, or definitely not present. The OCT testing was performed and interpreted by trained technicians, masked to the physicians' assessment of foveal edema. Agreement between OCT and contact lens examination for the absence or presence of foveal edema was evaluated. Results: One hundred seventy-two eyes of 95 patients with diabetes were enrolled in August and September 2002. Foveal thickness was objectively measured by OCT in 170 (99%) of 172 cases. We found excellent agreement between OCT and contact lens examination for the absence or presence of foveal edema when OCT thickness was normal (less than or equal to200 mum) or moderately to severely increased (>300 mum). However, agreement was poor when foveal thickness was mildly increased on OCT (201-300 mum). Conclusions: Agreement between contact lens examination and OCT for the detection of diabetic foveal edema is poor when OCT thickening is mild. This suggests that contact lens biomicroscopy is relatively insensitive for the detection of mild foveal thickening apparent on OCT. Additional studies are needed to investigate the natural course of cases with mildly increased foveal thickness on OCT that do not appear thickened clinically.