- Presenting feature of MS 15-20%
- Progresses over hours to days
- Typically unilateral
- 90% w/vague pain→ worse w/eye movement
- 75% recover acuity
- Decreased acuity
- Often central field loss
- 1/3 w/abnormal appearing optic disc
- Sometimes afferent pupil defect→ constricts when light shined in unaffected eye, but not to direct light