The effect of vergence vision training on binocularly normal subjects

Vergence is the disjunctive (inward or outward) movement of the eyes that is stimulated by retinal disparity (difference of where an image is projected to the retina and the fovea). A recent randomized clinical trial showed the efficacy of vision therapy for children with the binocular dysfunction known as convergence insufficiency is 73%. However, it is unknown whether binocularly normal persons will have any significant change to their vergence ocular motor system if they participate in vision training sessions. A total of ten (n = 10) binocularly normal persons participated in this study (18 to 28 years of age). A haploscope with an integrated infrared video-based eye tracking system manufactured by ISCAN presented vergence stimuli to the subject to record eye movement data before and after 12 hours of vision therapy with a custom LabVIEW program. Vision therapy entailed a random walk of 2° and 4° steps at near and far space along with ramps ranging from 1° to 20° of total vergence angular rotation. All processing and statistical analyses were conducted in MATLAB. All subjects experienced a significant decrease in time to peak velocity (p\u3c0.05). However, each subject’s peak velocity values were subject dependent and either increased, decreased, or maintained at the same level after training. The peak velocity of responses to 2° steps began to approach a more critically damped linear control system after vision training supporting an improvement in the accuracy of responses. Data support that even in binocularly normal control subjects; vision therapy improves vergence eye movements quantified as significant improvements in the time to fuse the new target and significantly more accurate responses compared to each subject’s baseline measurements