[Histopathological study of retinopathy of prematurity]

Using light and electron microscopy, we studied the histopathological findings of retinopathy of prematurity (zone II, stage 3). The infant was born at 32-week gestational period and the birth weight was 1,255 g. He suffered from intracranial hemorrhage and hydrocephalus, and died at 78 days old. The ophthalmoscopic findings of both eyes at 72 days after birth showed that the intermedia was clear. The optic disc and posterior pole showed normal findings. Ridge formation with non-vascularized retina was seen at the equator of all quadrants of the fundus except the nasal quadrant of retina. Light and electron microscopic studies showed the following; in the most periphery of the vascularized retina, endothelial cell proliferation with the capillary lumen of glomeruloid tufts (rearguard) were seen. There were the aggregation of immature mesenchymal cells (vanguard) near to the rearguard. The cytoplasmic organelles of spindle cells in the non-vascularized retina were different from those of surrounding glial cell. Therefore, they were thought to be mesenchymal cells in the non-vascularized retina. Between the vanguard and the rearguard, the proliferative tissues composed of immature endothelial cells and mesenchymal cells extended into the vitreous body through the inner limiting membranes, and they formed the fibrovascular membranes on the retina. It was concluded that fibrovascular proliferation on the retinal surface in the active case of retinopathy of prematurity was composed of immature endothelial cells with vascular lumen and mesenchymal cells.