ASTHENOPIA INDUCED BY COMPUTER-GENERATED FUSIONAL VERGENCE TARGETS

A questionnaire was used to evaluate asthenopia in 30 normal subjects (Ss). Then, each S experienced 3 min of continuous alternating convergent and divergent fusional vergence or a control condition which was identical to the experimental condition, but without any vergence demand, i.e., version. The stimulus was a computer-generated flat fusion red-blue anaglyph picture of a horse. The order of vergence and version conditions were randomized. Asthenopia measures and maximal fusional vergence ranges measures were repeated immediately after each condition. Results indicated a significantly higher rating of asthenopia after induced vergence than version. There were no differences in maximal fusional vergence ranges or recovery values after the two conditions. Correlations between pretreatment asthenopia scores and asthenopia scores after either induced vergence or version were also not significant. Post hoc analyses of Ss grouped as having either high or low asthenopia, according to baseline ratings, revealed no significant differences in vergence or version conditions. Alternative hypotheses for these results are resented.