An investigation of ultramarathon-associated visual impairment.

Objective: The purpose of this study was to investigate the characteristics under which ultramarathon-associated visual impairment occurs and to seek to identify its physiological basis and risk factors.

Methods: Through an online questionnaire, distributed worldwide, we obtained information from 173 self-identified ultramarathon runners who had experienced visual impairment during an ultramarathon. We attempted to characterize this vision impairment-its symptoms, duration, and the conditions under which it occurs. Select characteristics were compared with a reference group of 412 registrants of the 161-km Western States Endurance Run.

Results: Ultramarathon-associated visual impairment was typically characterized as painless clouding of vision that resolved either during (13.5%) or after racing within a median of 3.5 hours (range 0 to 48 hours) upon cessation of running. The mean (±SD) distance at which vision impairment occurred was 73±40 km, and the 161-km distance was the most frequent race distance (46.8%) in which visual impairment occurred. Visual impairment was often recurrent, with respondents reporting having it develop during a median of 2 races. Respondents with a history of refractive surgery had more episodes than those without such history (median 3.5 vs 2 episodes, P=.010). Compared with the reference group, runners with visual impairment were nearly twice as likely (23.7% vs 12.1%, P<.001) to have had refractive surgery.

Conclusions: Ultramarathon-associated visual impairment typically presents as a painless clouding of vision that is self-limited but tends to recur in certain runners. Risk appears higher among those with a history of refractive surgery, which is relevant for ultramarathon runners who are considering, or who have a history of, refractive surgery.