[Functional integrity of neural retina in 2. type diabetics]

The purpose of this prospective longitudinal study was to investigate early defects in functional integrity of neural retina in 2. type diabetic patients without or with mild diabetic retinopathy (DR) since there is an evidence of early functional changes in neural retina before occurrence of clinical manifestation of DR. Psychophysical test of contrast sensitivity (CS) was used for the detection of these changes. Relation between CS and systemic risk factors (HbAlc, blood pressure (BP), serum lipids and BMI) were also evaluated during a follow-up time. There were 48 recent diabetics without DR included in this study that were examined 3 times and compared to 23 diabetics with mild DR. The CS tests were performed using both Sine Wave Contrast Test (SWCT) and Pelli-Robson (PR) test. The reference values for CS threshold were derived from a CS of a control group of 52 healthy individuals. Abnormal CS ascertained by both methods, SWCT and PR, was observed in diabetics with mild NPDR. In comparison to the control group, there was a statistically significant difference of CS in spatial frequencies (SF) of 1.5, 6, 12, 18 cycles per degree (cy/deg). In comparison to diabetics without DR there was a significant difference of CS in SF of 6, 12 and 18 cy/deg in diabetics with mild NPDR. Abnormal CS was noticed in 47.8% (SWCT) or 21.7% (PR) of diabetics with DR. Statistically significant influence of high systolic BP on CS values and visual acuity was noticed. There were no abnormalities in CS in patients without DR comparing to control group during the whole follow-up. However, there was an improvement of CS in SF of 18 cy/deg observed between 1. and 3. evaluation of CS. Interaction of change in values of HbAlc and total cholesterol to HDL ratio had significant influence on CS improvement. Diabetics without DR had significantly better diabetes and blood pressure control in comparison to the diabetics with DR. In conclusion, it was not proved in this study that CS test is suitable for the screening for DR or early functional defects in neural retina before clinical manifestation of DR. Early diagnosis of DM and good compensation of diabetes, blood pressure and serum lipids level can postpone the onset of DR as well as the visual functions impairments.