Changes in visual function during the Coriolis illusion.
BACKGROUND
The Coriolis illusion produces spatial disorientation and is, therefore, dangerous for pilots. It is not known whether it also affects visual function (visual acuity and stereopsis).


METHODS
There were 18 subjects (15 men and 3 women, mean age 24.7 yr) enrolled in the study. A spatial disorientation simulator was used to produce Coriolis stimulation. The visual acuity of the subjects was evaluated with the Rosenbaum Vision Card before and during Coriolis stimulation. Stereopsis was measured with the Titmus stereo test. Throughout the experiments, eyeball movements were observed on a television monitor. Electrooculography (EOG) and electroencephalography (EEG) were also documented.


RESULTS
Before Coriolis stimulation, the visual acuity and stereopsis of all subjects were 20/20 and 40 s of arc, respectively. During the Coriolis illusion, the visual acuity of nine subjects (50%) remained 20/20, whereas the visual acuity of the others (50%) dropped by two lines. The stereopsis of most subjects (77.8%) decreased to 800 arc-seconds or less. Rhythmic nystagmus was observed, while EOG amplitudes were significantly elevated compared with those at baseline (9.41 +/- 0.26 microv2 and 8.45 +/- 0.36 microv2, respectively). EEG activity (frequency) was also greater than at baseline (13.15 +/- 0.84 Hz and 11.94 +/- 1.20 Hz, respectively; P < 0.05).


CONCLUSIONS
During Coriolis stimulation, the visual acuity of the subjects remained stable, but their stereopsis was reduced. Further study is warranted.
Horng
Chi-Ting
CT
Department of Ophthalmology, Kaohsiung Armed Force General Hospital, Kaohsiung, Taiwan.
Liu
Chung-Cheng
CC
Kuo
Daih-Iluang
DI
Shieh
Po-Chuen
PC
Wu
Yi-Chang
YC
Chen
Jiann-Torng
JT
Tsai
Ming-Ling
ML
D000328:Adult; D000337:Aerospace Medicine; D015331:Cohort Studies; D003198:Computer Simulation; D003221:Confusion; D003312:Coriolis Force; D003867:Depth Perception / Q000502:physiology*; D004569:Electroencephalography; D004585:Electrooculography; D005260:Female; D006112:Gravitation; D006801:Humans; D008297:Male; D012027:Reflex, Vestibulo-Ocular; D014792:Visual Acuity / Q000502:physiology*