Distance Stereoacuity. Assessing Control in Intermittent Exotropia

Background: A patient's ability to control an intermittent exotropic deviation is usually assessed by subjective means such as observation of control in the office, questioning the patient and/or family about control at home, and reports of monocular eye closure in bright light. An objective method of assessing control has not been developed.

Purpose: The purposes of this study are to determine if distance stereoacuity was different in patients with intermittent exotropia than in normal subjects and to determine if distance stereoacuity could be used as a objective means of assessing control in intermittent exotropia.

Methods: The authors evaluated near and distance stereoacuity in 44 patients with intermittent exotropia and 50 normal subjects. Patients with intermittent exotropia also were assessed for office control, home control, and monocular eye closure in bright light. Additionally, six patients who underwent successful surgery were reevaluated postoperatively.

Conclusion: Normal subjects and patients with intermittent exotropia had good near stereoacuity. Patients with intermittent exotropia demonstrated significantly worse distance stereoacuity than the population of normal subjects (P < 0.001). Five of six patients with poor distance stereoacuity preoperatively had dramatic improvement in distance stereoacuity postoperatively. Diminished distance stereoacuity seems to be an objective measure of poor control of the exotropic deviation. This test may provide important objective criteria for deciding when to perform surgery in patients with intermittent exotropia.