BACKGROUND Retinal cotton-wool spots (CWSs) are an important manifestation of retinovascular disease in hypertension (HTN) and diabetes mellitus (DM). Conventional automated perimetry data have suggested relative scotomas in resolved CWSs; however, this has not been well delineated using microperimetry. This study evaluates the retinal sensitivity in documented resolved CWSs using microperimetry. METHODS Retinal CWSs that resolved after 10 to 119 months (median, 51 months) and normal control areas were photographed to document baseline lesions. Eye-tracking, image-stabilized microperimetry with simultaneous scanning laser ophthalmoscopy was performed over resolved CWSs, adjacent uninvolved areas near the lesion, and in location-matched normal patients (age-matched). RESULTS A total of 16 eyes in patients with DM or HTN (34 resolved CWSs) and 16 normal control eyes (34 areas) were imaged. The mean (SD) sensitivity of resolved CWSs in the eyes of patients with HTN and DM was 11.67 (3.88) dB and 7.21 (5.48) dB, respectively. For adjacent control areas in the eyes of patients with HTN and DM, the mean (SD) sensitivity was 14.00 (2.89) dB and 11.80 (3.45) dB, respectively. Retinal sensitivity was significantly lower in areas of resolved CWSs than in the surrounding controls for patients with HTN (P = .01) and those with DM (P < .001). Scotomas in patients with DM were denser than those of patients with HTN (P < .05). CONCLUSIONS Cotton-wool spots in patients with DM and HTN leave permanent relative scotomas detected by microperimetry. Scotomas are denser in eyes of patients with DM than in those with HTN. In addition, among patients with DM, adjacent retinas not involved with CWSs have lower retinal sensitivity than in age-matched controls.