In previous generations, when survival depended on the ability to hunt, fish, and farm, the visual system had to respond to constantly changing, distant stimuli. Good distance visual acuity and stereoscopic vision were of paramount importance. Today, the emphasis has shifted from distance to two-dimensional near vision tasks such as reading, desk work, and computer viewing. In some persons, the visual system is incapable of performing these types of activities efficiently either because these tasks lack the stereoscopic cues required for accurate vergence responses or because the tasks require accommodative and vergence functioning that is accurate and sustained without fatigue. When persons who lack appropriate vergence or accommodative abilities try to accomplish near vision tasks, they may develop ocular discomfort or become fatigued, further reducing visual performance.
Accommodative and vergence dysfunctions are diverse visual anomalies. Any of these dysfunctions can interfere with a child’s school performance, prevent an athlete from performing at his or her highest level of ability, or impair one’s ability to function efficiently at work. Those persons who perform considerable amounts of close work or reading, or who use computers extensively, are more prone to develop signs and symptoms related to accommodative or vergence dysfunction.
Symptoms commonly associated with accommodative and vergence anomalies include blurred vision, headache, ocular discomfort, ocular or systemic fatigue, diplopia, motion sickness, and loss of concentration during a task performance. The prevalence of accommodative and vergence disorders, combined with their impact on everyday activities, makes this a significant area of concern.