Morphological and functional analyses of diabetic macular edema by optical coherence tomography and multifocal electroretinograms

Purpose: To determine the correlation between the tomographic features and the visual functions of eyes with diabetic macular edema. Methods: Optical coherence tomographic (OCT) images and multifocal electroretinograms were obtained from 45 eyes of 25 patients with diabetic macular edema and from 21 eyes of 21 normal subjects. Results: The OCT images showed cystoid macular edema in 18 eyes and diffuse retinal swelling without cystoid edema in the other 27 eyes. The fovea was significantly thicker in eyes with cystoid macular edema and in those with diffuse retinal swelling than in normal eyes. The fovea of eyes with cystoid edema was significantly thicker than the fovea of eyes with diffuse swelling. The best-corrected visual acuity and the electrical response density from the macular area were significantly reduced in eyes with diabetic macular edema, particularly in those with cystoid edema. The best-corrected visual acuity and macular response density of the multifocal ERGs were inversely correlated, and the implicit times were directly correlated with foveal thickness. Conclusion: The visual acuity was correlated significantly with morphological changes revealed by OCT and with multifocal ERGs. The combination of OCT and multifocal ERGs may provide objective criteria for the evaluation and assessment of diabetic macular edema.