[Comparative ultrastructural analysis of the proliferative tissue in PDR patients with or without vitreous haemorrhage: from ultrastructural approach to clinical practice].

BACKGROUND: Proliferative diabetic retinopathy (PDR) is a sight-threatening disease with high social impact, easily complicated with vitreous haemorrhages (VH). In our study we try to point out the ultrastructural differences between proliferative tissues in PDR patients with and without vitreous haemorrhage in regard to the clinical practice and proper timing of vitreo-retinal surgery.

MATERIAL AND METHODS: In our prospective study we included 27 PDR patients (18 with PDR only and 9 with PDR and vitreous haemorrhage). All of them were later operated with pars plana vitrectomy, during which proliferative tissue was collected. The materials were examined with transmission and scanning electron microscopy and histochemically with Safranin O.

RESULTS: The proliferative tissue of PDR patients without VH was mainly comprised of fibroblasts, macrophages and glial cells. We found a variety of blood vessels. Most common were the capillaries of "mature" new vessels. In the proliferations of patients with VH, macrophages and erythrocytes were more commonly detected. In the tissue capillaries of young new vessels prevailed, with only a very thin layer of endothelial cells comprising their walls. In the extracellular matrix among the proteoglycan complexes, we found lots of residual elements of blood.

CONCLUSIONS: Our results point out that blood in the vitreous cavity alters the ultrastructure of the existing PDR proliferations in respect to making them more rigid and prone to contractions. It is therefore important to consider vitreous haemorrhage in PDR patients as a very serious complication, requiring in some cases urgent vitreo-retinal surgery.