Abnormal Electroretinography in Patients with Long-Duration Diabetes but No Retinopathy

Retinopathy increases with duration of diabetes but the presence of this microvascular complication in individual patients remains unpredictable. Retinal neurophysiological changes have been postulated to be important in modulating susceptibility. We performed electroretinography (ERG) on patients with long duration of diabetes (>15 years) but no retinopathy to determine whether this setting of “normal retinal morphology” is also characterised by normal electrophysiology of the eyes. ERG was performed with a handheld RETeval-DR™ device. Flickering lights at 30Hz was used to stimulate retinal electrical activity recorded by skin electrodes placed below the lower eye lids. Implicit time (electrical conduction time, msec), amplitude (uV) and pupil diameter (mm) were recorded. A composite score < 20 of these three parameters indicates a <1% risk of vision threatening retinopathy. Altogether 26 type 2 and 9 type 1 patients with no retinopathy and diabetes duration 22.5±4.5 and 32.8±9.4 years respectively were studied. Nondiabetic individuals (fasting BGL<6.0mM or HbA1c<6.0% n=25) acted as controls. Results in Table 1 showed the implicit time of individuals with diabetes but no retinopathy was only minimally increased but the amplitude was significantly reduced by ∼30% (p<0.01). We conclude that the eyes of these patients protected from diabetic retinopathy nevertheless showed retinal neural dysfunction. Disclosure B. Brooks: None. D. Yue: None. E. Landy: None. Y. Shi: None.