[The role of the osmotic pressure of the blood in the pathogenesis of diabetic changes in the retina].

Based on the regularities of circulation mechanics, the authors hypothesize the role of osmotic pressure in the development of diabetic changes in the retina. A mathematical model of tissue fluid movement based on this hypothesis shows that transmural pressure in choriocapillaries is higher than in exchange vessels of the retina, and therefore unidirectional fluid flow from choriocapillaries to these vessels develops. A sharp increase in glucose concentration is paralleled by an increase in osmotic pressure, which, in turn, creates a negative hydraulic pressure in retinal tissue and leads to overstretching of exchange vessels and appearance of microaneurysms. One of pathogenetically based therapeutic effects of laser coagulation in diabetic retinopathy is creation of "fenestrae" in the retinal pigmented epithelium, facilitating tissue fluid movement.