Diabetes Care, Vol 15, Issue 5 620-625, Copyright © 1992 by American Diabetes Association
Nonselective loss of contrast sensitivity in visual system testing in early type I diabetes
MA Di Leo, S Caputo, B Falsini, V Porciatti, A Minnella, AV Greco and G Ghirlanda
Department of Internal Medicine, Catholic University, Rome, Italy.
OBJECTIVE--Psychophysical methods in patients with diabetes mellitus reveal
deficits of central or foveal vision. Our aim was to evaluate the
contrast-sensitivity thresholds in 24 insulin-dependent (type I) diabetic
patients with a short disease duration and without retinopathy, taking into
account metabolic control. RESEARCH DESIGN AND METHODS--The control group
consisted of age-matched nondiabetic subjects. None had visual or systemic
symptoms. Contrast sensitivity measured at eight different spatial
frequencies to sinusoidal bar patterns of 0.6-12.2 cycles/deg can detect
functional defects in the spatially sensitive retinal ganglion cells or in
higher visual pathways. We performed two different temporal types of
contrast-sensitivity testing, dynamic (8 Hz) and static (0 Hz).
RESULTS--Significant losses with dynamic contrast-sensitivity test at all
but the highest spatial frequencies (i.e., 12.2 cycles/deg) were shown,
whereas there was significant attenuation of contrast sensitivity at five
spatial frequencies (1.0, 1.4, 2.2, 7.1, and 9.6 cycles/deg) in the static
mode. Grating losses (less than 2SD of control means) of contrast
sensitivity were found in 33.3% (dynamic) and in 72.9% (static) of eyes of
diabetic patients. HbA1c values were positively correlated at variable
spatial frequencies (1.0, 1.4, and 2.2 cycles/deg for dynamic test and 0.6,
1.0, 1.4, 2.2, 4.8, and 7.1 cycles/deg for static test). CONCLUSIONS--Our
results suggest an early, generally nonselective neuronal damage of visual
pathways that occurs before the onset of clinically detectable retinopathy.
The visual deficit may be related directly to the effects of diabetes;
repetitive minor hypoglycemic insults may contribute more than a marked
hyperglycemic condition to the mechanisms underlying physiological changes
along the optic nerve.