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 (PBRB) was determined by vitreous fluorophotometry with correction for autofluorescence, lens transmission 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 PBRB by multiple regression analysis. The PBRB 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 greater than 0.3]. The PBRB was correlated to morphological abnormalities of (pre)proliferative retinopathy [(1) intraretinal microvascular abnormalities (SIRMA) and (2) new vessels (Sneo): PBRB = A+B.SIRMA + C.Sneo with PBRB in nm/sec, A = 1.5 +/- 0.5, B = 0.9 +/- 0.2 and C = 1.7 +/- 0.4, R2 = 0.65, p less than 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.