Ultrastructural characteristics of proliferative tissue in retinopathy of prematurity.

We examined the histologic and ultrastructural characteristics of 27 membranes (from 18 patients) removed during vitreous surgery for partial and total retinopathy of prematurity. In membranes removed anteriorly from a child with active disease, we found vessels that had characteristics of developing neovascularization. In the membranes from older infants with inactive disease (16 patients), glial cells were common and vessels, if present, had more mature characteristics. Retinal glial cells (presumably Müller cells) were seen fragmenting the internal limiting lamina and migrating into the overlying vitreous by projecting long microvilli into the vitreous cavity. Anterior membranes (13 patients), particularly in active disease, were likely to contain vessels, whereas posterior membranes (five patients) were more often avascular and were composed of glial cells.