EFFECT OF MORPHOLOGICAL ABNORMALITIES ON BLOOD RETINAL BARRIER PERMEABILITY IN DIABETIC-RETINOPATHY

The morphological base for the impaired function of the blood retinal barrier was studied in 50 eyes of 10 insulin dependent and 21 non-insulin dependent patients with various levels of diabetic retinopathy. The permeability of the blood retinal barrier (P(BRB)) was determined by vitreous fluorophotometry with correction for autofluorescence, lenstransmission and non-protein bound plasma fluorescein concentration. Morphological abnormalities of diabetic retinopathy assessed by fundus photography and fluorescein angiography were individually scored on a decimal scale and related to the P(BRB) by multiple regression analysis. The P(BRB) was not correlated to morphological abnormalities of non-proliferative retinopathy [(1) microaneurysms, (2) hard exudates, (3) soft exudates, (4) intraretinal hemorrhages, (5) fluorescein leakage, and (6) capillary closure, p > 0.31. The P(BRB) was correlated to morphological abnormalities of (pre)proliferative retinopathy [(1) intraretinal microvascular abnormalities (S(IRMA)) and (2) new vessels (S(neo)): P(BRB) = A + B.S(IRMA) + C.S(neo) with P.. in nm/sec, A = 1.5 +/- 0.5, B = 0.9 +/- 0.2 and C = 1.7 +/- 0.4, R2 = 0.65, p < 0.0001]. It can be concluded that the increased blood retinal barrier permeability in diabetic patients is mainly due to (pre)proliferative abnormalities and not to non-proliferative abnormalities.