Protein S and protein C are vitamin K-dependent plasma proteins that modulate coagulation. Protein C deficiency has been reported in association with amaurosis fugax,1 and it has been suggested that there may be an association of protein C activity with branch retinal vein occlusion.2 We have recently cared for a patient with protein S deficiency and a central retinal artery occlusion.
Report of a Case.
—A 30-year-old man developed transient episodes of vision loss in the left eye, each lasting about 3 minutes. Visual acuity was 20/100 OS. The anterior segment was normal, and the intraocular pressure was 15 mm Hg. The disc was normal. There was narrowing of the retinal arterioles and mild dilatation of the retinal veins. No retinal emboli were present. He was being treated with sodium warfarin (Coumadin), and the prothrombin time was 15.7 seconds, with a reference range of 9.8 to 11.4 seconds.