Effects of relaxation and aversive visual stimulation on dark focus accommodation.

There is evidence that sympathetic innervation induces decreases in accommodation or accommodation amplitude. If so, emotional stress that produces sympathetic activation should induce similar changes in accommodation. In two experiments, dark focus accommodation was assessed following deep relaxation and after subjects looked at gruesome slides. Results showed that stress exposure led to lower dark focus values than did relaxation. Further, the degree to which dark focus was affected depended on subjects' levels of perceived arousal, and on the degree of stressfulness represented by the slides. It was concluded that psychological stress can produce predictable changes in accommodation, changes most parsimoniously understood in terms of autonomic innervation of the ciliary body.