Early functional changes in the diabetic retina seem to occur before morphological changes in the RNFL.

Aim Diabetes mellitus (DM) is a systemic disease with insufficient secretion of insulin or poor response to insulin. This typically causes poor control of blood glucose level leading to a range of complications. Early detection of the retinal function alteration in DM is needed. Methods A newly modified paradigm-slow double-stimulation multifocal electroretinogram (mfERG)-was introduced to measure early changes of retinal function in DM and to investigate changes in the adaptation mechanisms in the diabetic retina. The mfERG was measured by using a slow double-stimulation mfERG paradigm (M(1)M(2)OOO). Results The m1 amplitude of M(1) stimulation from diabetic subjects was significantly reduced in ring 1 in contrast to that of a control group. The m2 amplitude of M(2) stimulation from diabetic subjects was also significantly reduced in ring 1 and 2 as compared with those of the control group. The m1/m2 ratio which minimises intersubject variation shows a reasonable differentiation between the control and diabetic groups. There was a significant increase in the amplitude ratio from diabetic subjects in ring 2 and 3 as compared with those of the control group. Conclusions The present findings suggest that the new mfERG paradigm is a fast and sensitive test for the detection of early functional changes in the diabetic retina.

This stimulation paradigm provides a method of measuring temporal visual characteristics. The M(1):M(2) ratio acts as an indirect functional indicator of retinal adaptation, which may be abnormal in the diseased retina. Further development of this method may help to describe the functional variation in the diseased retina and to predict the occurrence of a range of retinopathies.

The MOFO mfERG can help in detecting early functional anomalies before the appearance of visible signs, and may assist in monitoring further functional deterioration in diabetic patients.

The g/f ratio is important in the MOFO mfERG paradigm, since the DC and IC responses change with this ratio. In order to obtain both optimal DC and IC responses, a g/f ratio of 1:1 with focal flash luminance between 100 cd/m(2) and 200 cd/m(2) would be recommended. As the global flash mfERG paradigm is studying the interaction triggered by both flashes, the g/f ratio is a vital parameter for measurement in future studies.