The mystery of cotton-wool spots - a review of recent and historical descriptions.

PURPOSE Cotton-wool spots (CWSs) lie superficially as opaque swellings in the retina, with occurring as acute lesions. The occurrence of CWSs is a sign of serious vascular damage. METHODS CWSs can usually be diagnosed by ophthalmoscopy. In the literature, there are reports of examinations by fluorescein angiography, visual fields, or optical coherence tomography (OCT). RESULTS CWSs are non-specific, as they can occur in different diseases involving the retinal vascular system. CWSs are localized accumulations of axoplasmic debris within adjacent bundles of ganglion cell axons. They occur after arteriolar occlusion at the borders of large ischemic areas, and should not be regarded as retinal fiber layer infarcts (McLeod). The "principal constituent of the CWS" are cytoid bodies. Microaneurysms may be present at the edge of some CWSs in different diseases with retinal ischemia. The presence of many CWSs may be a significant predictor for the development of rubeosis iridis, for instance in a patient with central retinal vein occlusion. CWSs have disappeared in weeks or occasionally a few months in hypertensive patients. However, in diabetic patients, they may persist for as long as one or two years. CWSs have been the most frequent ocular findings in patients with Aids. Aids patients show a strong correlation between CWSs and multiple opportunistic infections. Aids patients with CWSs have shown a poorer prognosis compared to those without CWSs. Leukocyte counts were found to be significantly lower, and the proportion of patients with significant weight loss was greater among Aids patients who revealed CWSs. CONCLUSION CWSs delineate ischemic retina, which is attributed to obstruction of axoplasmic transport. Ischemia is the essential factor in the development of CWSs. Early detection of a CWS is necessary to evaluate a hitherto occult systemic disease with a vascular component.