Horwood, A, Toor,S , Riddell P JAAPOS 2014. Published online 28 Feb 2014
- Simple (rather than complex) convergence exercises, and just being encouraged to try harder, resulted in greatest improvements in objective convergence and accommodation after a short course of treatment.
Although eye exercises appear to help heterophoria, convergence insufficiency, and intermittent strabismus, results can be confounded by placebo, practice, and encouragement effects. This study assessed objective changes in vergence and accommodation responses in naive young adults after a 2-week period of eye exercises under controlled conditions to determine the extent to which treatment effects occur over other factors. Asymptomatic young adults were randomly assigned to one of two no-treatment (control) groups or to one of six eye exercise groups: accommodation, vergence, both, convergence in excess of accommodation, accommodation in excess of convergence, and placebo. Subjects were tested and retested under identical conditions, except for the second control group, who were additionally encouraged. Objective accommodation and vergence were assessed to a range of targets moving in depth containing combinations of blur, disparity, and proximity/looming cues. A total of 156 subjects were included. Response gain improved more for less naturalistic targets where more improvement was possible. Convergence exercises improved vergence for near across all targets (P = 0.035). Mean accommodation changed similarly but non-significantly. No other treatment group differed significantly from the non-encouraged control group, whereas encouraging effort produced significantly increased vergence (P = 0.004) and accommodation (P = 0.005) gains in the second control group. True treatment effects were small, significantly better only after vergence exercises to a non-accommodative target, and rarely related to the response they were designed to improve. Exercising accommodation without convergence made no difference to accommodation to cues containing detail. Additional effort improved objective responses the most.