[Changes in the second-order kernel component obtained by the techniques of the multifocal electroretinogram in early stages of diabetes mellitus]

To detect changes in retinal function in diabetic eyes without ophthalmoscopic retinopathy and to find a clue for differential origins of the second-order kernel of the multifocal electroretinogram(m-ERG).

m-ERGs were recorded from eyes of 22 healthy control subjects and 21 patients with diabetes mellitus(DM) by 19-hexagonal-element stimulus at stimulus intensities of 20, 63, 100, 200 and 331 cd/m2(VERIS III, Tomey). The response densities and the peak latencies of the first-order kernel(P 1) and the second-order kernels(P 2, P 3) were compared between the DM and the control groups. Full-field ERGs were also recorded from the same patients and compared with the results of m-ERGs.

The response densities of P 1 and P 2 in the DM group were significantly(p < 0.05) larger than those in the control group. The response of the full-field ERG in the DM group did not significantly differ from that in the control group. The components of the m-ERG were divided into two groups based on their behavior to stimulus intensity changes: P 1 together with P 2 and P 3. With increase in the stimulus intensity, the response densities of P 1 and P 2 increased significantly(p < 0.05), while the response densities of P 3 did not change significantly.

The fact that the response densities in the DM group were greater than those in the control group supports the hypothesis that the retinal blood flow increases in the early stage of diabetes. m-ERG is therefore beneficial to ascertain subclinical retinal changes and to evaluate the retinal function of early diabetic patients. Since the P 2 and P 3 differed in behavior according to the stimulus intensities, it can be inferred that origin of the P 2 of the second order kernel is different from that of P 3.