Electron microscopic studies of pipestem sheathed vessel in human retina.

Histopathology of a clinically observed pipestem sheathed vessel in the retina was studied by electron microscopy. This vessel was characterized by a marked increase and disarrangement of collagen fibrils in the media and adventitia, and invasion of the cytoplasmic processes of Müller cells into the adventitia. The lumen of the vessel was extremely narrow but was preserved with healthy endothelial cells. It is suggested that increased and disarranged collagen fibrils in the vessel wall is related mainly to the ophthalmoscopic appearance of the pipestem sheathing. The infiltration of glial cells in the vessel wall may be of less significance to the pipestem sheathing.