CHANGES IN THE DARK FOCUS OF ACCOMMODATION ASSOCIATED WITH SIMULATOR SICKNESS

The relationship between the dark focus of accommodation and simulator sickness, a form of motion sickness, was examined in three experiment s. In Experiment 1, dark focus was measured in 18 college students in a laboratory setting before and after they viewed a projected motion s cene depicting low altitude helicopter flight. In Experiments 2 and 3, dark focus was measured in pilots (N = 16 and 23, respectively) befor e and after they ''flew'' in moving-base helicopter flight simulators with optical infinity CRT visual systems. The results showed that indi viduals who experienced simulator sickness had either an inward (myopi c) change in dark focus (Experiments 1 and 3) or attenuated outward sh ifts in dark focus (Experiment 2) relative to participants who did not get sick. These results are consonant with the hypothesis that parasy mpathetic activity, which may be associated with simulator sickness, s hould result in changes in dark focus that are in a myopic direction. Night vision goggles, virtual environments, extended periods in microg ravity, and heads-up displays all produce related visual symptomatolog y. Changes in dark focus may occur in these conditions, as well, and s hould be measured.