Experimental macular edema of commotio retinae: preliminary report.

Experimental macular edema of commotio retinae was studied in rhesus monkeys. Clinically, opacification of the retina in these experimental animals closely resembled commotio retinae of man. No pigment epithelial damage was detected by ophthalmoscopy and fluorescein angiography showed no leakage from the retinal and choroidal circulations in the macular region. Histologically, macular swelling was apparent and was due primarily to changes of the outer plexiform layer. In this layer, swelling of the axons of the photoreceptor cells was prominent. Intracellular edema was also detected in the Müller cell processes in the inner retina and in the pigment epithelial cells. Prominent changes also occurred in the inner and outer segments of the photoreceptor cells. Disruption of the blood-retinal barrier was not found using horseradish peroxidase as a tracer. We concluded that retinal opacification was due to disagreement and intracellular edema of the cellular elements of the retina, perhaps a direct result of movement of intracellular fluid in response to mechanical injury.