Abstract
Purpose: :
The pathogenesis of diabetic retinopathy is complex and still remains incompletely understood. The diabetic retinopathy is usually considered as a retinal microangiopathy. However, an increasing number of studies suggest that the impairment of retinal neural cells may precede the earliest signs of retinal vascular impairment. The aim of the study was to assess in a controlled study the retinal functional abnormalities in diabetic patients without clinical appearance of retinopathy.
Methods: :
Twenty-eight patients with diabetes (11 patients with type 1 diabetes, 17 patients with type 2 diabetes) without diabetic retinopathy on fundus examination, and 28 age- and sex-matched healthy volunteers were included. Each subject underwent a complete ophthalmologic examination, a color vision test (Lanthony D-15 desatured color test), a contrast sensitivity test (Peli-Robson test), a pattern-ERG, a full-field ERG, and a multifocal ERG, according to the ISCEV guidelines. The comparison of the results between the 2 groups were assessed using the Student-t test. P< 0.05 were considered as the level of significance.
Results: :
In diabetic patients, the total color difference score at the D-15 desatured color test was significantly higher than in healthy volunteers. The implicit times of the oscillatory potentials were significantly longer and the oscillatory potential amplitudes were significantly lower in diabetic patients as compared with the healthy volunteers. The implicit times of the N35 and N95 waves at the pattern-ERG were significantly longer, and the amplitudes of the P50 and N95 waves were significantly lower; the b-wave implicit time at the rod ERG and the a and b- wave implicit times at the single-flash cone ERG were significantly longer in diabetic patients as compared with the healthy volunteers.
Conclusions: :
Retinal functional abnormalities occurred in diabetic patients before the clinical appearance of diabetic retinopathy. The most early impaired retinal cells seem to be the amacrine and bipolar cells, the ganglion cells and cone photoreceptors cells. These results suggest that an early neurodegenerative process, which could precede the vascular impairment, may occur in diabetic retinopathy.
Keywords: diabetic retinopathy • electroretinography: clinical • retina: proximal (bipolar, amacrine, and ganglion cells)