Does order matter? Evaluating the impact of binocular vision test sequence

To assess the repeatability of common clinical tests of accommodative and vergence function and evaluate the impact of sequence of testing on outcomes.

Participants underwent a series of accommodative and vergence function tests under associated and dissociated conditions over 3 study visits. At the first study visit, participants were randomized to undergo associated or dissociated tests first. The testing order was reversed at the second visit (to evaluate sequence of testing), and the third visit replicated the order of testing of the first visit (to evaluate intersession repeatability). Associated tests (in order) included binocular modified push-in/out amplitude of accommodation, Fused Cross Cylinder, negative and positive relative accommodation, and binocular ±2.00 D lens flippers to assess accommodation, and Randot Stereo Test to measure local stereoacuity and fixation disparity. Dissociated tests (in order) were monocular modified push-in/out amplitude of accommodation, distance and near phorias measured with the Howell Phoria card and Modified Thorington test to assess vergence function, and monocular ±2.00 D lens flippers to assess accommodation.

There were no significant differences in binocular vision function measures when associated or dissociated tests were conducted first (all p < 0.003). Additionally, there were no significant differences in mean measures tested across the first and third study visits where testing sequence remained consistent. Push-in/out methods to measure binocular and monocular accommodative amplitudes, ±2.00 D lens flippers to measure binocular and monocular accommodative facilities, horizontal distance and near phoria measured with the Howell Phoria card, and near phoria with the Modified Thorington test had ICC >0.75 indicating good intersession repeatability. All other tests had ICC <0.75 indicating poor repeatability of repeated measurements.

The sequence of testing of associated and dissociated techniques did not influence outcomes. Additionally, when the testing sequence was kept consistent between the first and third study visits, there were no statistically significant differences in accommodative and vergence function measures obtained with investigated methods. The generally high variability of some measurements across sessions suggests that individual techniques alone may not reliably detect clinically meaningful changes in accommodation or vergence function and a battery of tests is likely needed for monitoring binocular vision disorders.