Cotton-wool spots and retinal light sensitivity in diabetic retinopathy. In 14 eyes of 14 patients with diabetic retinopathy the light sensitivity of retinal cotton-wool spots was studied by computerised perimetry, and the visual field data were accurately correlated with the corresponding morphology as seen on fundus photographs and fluorescein angiograms. In 12 of the eyes the examinations were repeated within one year in order to follow changes in retinal light sensitivity during the evolution of the lesions. Retinal cotton-wool spots were in all eyes associated with localised non-arcuate scotomata in the visual field. In four eyes the cotton-wool spots disappeared within three months of the first examination, and in two of these cases the corresponding scotomata disappeared together with the morphological lesions. In eight eyes the cotton-wool spots (and the corresponding scotomata) had not resolved one year after the first examination. The mean blood pressure showed no significant difference between the patients in whom the lesions resolved within three months and the patients in whom the lesions persisted longer. 