To present a case of a single isolated cotton-wool spot in a healthy patient.

A 43-year-old woman with no systemic disease complained of sudden inferior field defect of the right eye. On fundoscopic examination of the right eye, a single soft white spot was observed in the superotemporal vascular arcade. An elevated hyper-reflective area in the inner retina corresponding to a white spot was observed on optical coherence tomography. Automated perimetry revealed an arcuate field defect which was wider than the cotton-wool spot. A complete workup for systemic diseases was within normal range except a positive rheumatoid factor. At the 2-week follow-up, the patient's subjective symptom improved and the white spot decreased. After 6 months, the cotton-wool spot disappeared and slit-like retinal nerve fiber layer (RNFL) defects corresponding to the location of the cotton-wool spot was noticed. One year later, disc and RNFL defect were unchanged but the previous field defect disappeared.

Isolated cotton-wool spots can occur without serious systemic diseases in healthy patients. A single isolated cotton-wool spot in the present case disappeared spontaneously leaving permanent structural damage on the retina over time.