Electroretinographic results and ocular vascular perfusion in type 1 diabetes

Although functional changes in vision are known to occur before overt diabetic retinopathy, the relationship between (1) the degree and timing of any visual dysfunction and (2) the duration and control of diabetes remains poorly defined. The authors compared the ability of patients with insulin-dependent diabetes mellitus and nondiabetic subjects to sustain normal retinal function during transient physiologic stress. Such provocative testing may be clinically useful to show subclinical dysfunction.

Retinal function during altered ocular perfusion pressure (OPP) produced by body inversion and scleral suction was quantified by scotopic white-flash electroretinography (ERG) in 11 young volunteers with insulin-dependent diabetes mellitus but without significant retinopathy and a group of normal subjects.

Baseline ERG a- and b-waves did not differ across test groups, but the a-wave implicit time was prolonged for diabetic patients. Furthermore, four of five oscillatory potentials (OP) in the diabetic patients were smaller than those in the nondiabetic subjects. Although the amplitude and implicit time of some OP in the diabetic patients were changed to a larger degree, the overall OP response profile did not differ widely from that for the nondiabetic subjects. Also, the a- and b-waves and the OP index for the test eye in diabetic and normal subjects did not differ, but the control eyes showed some differences in these parameters.

Retinal function and vascular autoregulation in young diabetic patients without visible retinopathy did not differ from those in nondiabetic subjects; they were reduced in both groups by a short-term attenuation of the OPP.