Patterns of abnormal binocular fixation in a symptom free subject with a well-controlled exophoria

Elaine Cornell, DipAppSc (Cumb) MA (Macq)

A case history is presented that illustrates six different patterns of binocular fixation in a symptom free subject with a moderate exophoria or convergence weakness type, following a vergence eye movement. This 19 year old student showed normal vergence resulting in binocular fixation, but also showed an insufficient vergence response, two types of saccadic responses, an unequal vergence response and a response where one eye converged for near fixation while the other eye remained fixing for distance.
Similar responses to these have been described by others in apparently normal subjects, who may represent a symptom free group able to make ready sensory adaptations to abnormal binocular fixation. Alternatively, the lack of diplopia in the presence of significant retinal disparity may be the result of a normal form of visual suppression that occurs briefly during, and just following a vergence eye movement, similar to that which occurs during a saccade.