FOVEAL CONE FUNCTION IN NONPROLIFERATIVE DIABETIC-RETINOPATHY AND MACULAR EDEMA

Purpose. To study results of foveal cone electroretinograhy (ERG) in p atients with nonproliferative diabetic retinopathy (NPDR), with and wi thout clinically significant macular edema (CSME). Methods. Electroret inograms of foveal cones were elicited, with a dual-beam stimulator-op hthalmoscope, from 18 consecutive patients with bilateral NPDR and uni lateral CSME. Results. Analysis of resulting data revealed that mean a mplitude was significantly lower in eyes with CSME and in eyes without CSME, compared with that in normal eyes, Mean implicit time was signi ficantly longer in eyes with CSME compared with that in normal eyes, b ut in eyes of diabetic patients without CSME, mean implicit time was t he same as that in normal eyes. Amplitudes were directly correlated an d implicit times were inversely correlated with best-corrected Snellen visual acuity in eyes with and without CSME. Eyes with CSME had signi ficantly lower amplitudes and longer implicit times than their fellow eyes without CSME. In addition, eyes with NPDR, with or without CSME, did not exhibit the normal rise in amplitude with increasing duration of light exposure. Conclusions. Electroretinographic findings showed a bnormalities in foveal cone responses in eyes with NPDR, particularly in the presence of CSME. These results may support a functional role f or outer retinal dysfunction in patients with diabetic retinopathy and loss of central vision.