Vergence refers to the simultaneous movement of the eyes in opposite directions to maintain binocular vision. There are different types of vergence including fusional vergence, proximal vergence, tonic vergence, and accommodative vergence. Vergence is measured through tests such as near point of convergence and AC/A ratio. Common vergence anomalies include convergence insufficiency, convergence excess, divergence insufficiency, and divergence excess, each characterized by specific symptoms and treatments.