Figure 1

A schematic illustration of some of the abnormalities associated with advanced ROP. In the early stages, ROP is characterized by an incomplete vascularization of the peripheral retina (panel A), with a sharply demarcated boundary between vascularized and avascularized retina (stage 1). This can progress to an elevated ridge (panel B) that consists of mesenchymal tissue (stage 2). In more advanced stages of the disease, extra-retinal fibrovascular proliferation occurs (panel C) on the posterior border of the ridge (stage 3). In addition to the abnormal vascularization, the normal gelatinous vitreous (panel D) becomes partially liquefied (panel E). While spontaneous regression often occurs, an organization and contraction of vitreous collagen can take place (panel E) which can lead to a retinal fold (panel F) causing partial (panel G) or total retinal detachment (panel H) that represent stages 4 and 5 respectively.