exotropia
Exotropia is a manifest strabismus with diverging visual axes.1 A constant exotropia is present if fusion cannot hold the eyes aligned under any circumstances.1 An intermittent exotropia appears only at certain times, as on waking from a nap or during tiredness, illness or stress.1
Constant exotropia of early onset often presents at birth with a large angle, and neurological anomalies are frequently present.2 Intermittent exotropia often presents at around 2 years of age as an exophoria that breaks down under visual inattention, bright light, fatigue or ill health.2 Exotropia can also be acquired later in life.2 Sensory exotropia follows visual loss from acquired lesions such as cataract or corneal scarring, and consecutive exotropia most often follows surgical correction of an esodeviation.2
The angle of exotropia may differ between distance and near fixation, and that difference is the basis of its classification.3 The angle may also change in upgaze or downgaze, producing A and V patterns.3
More detail
Exodeviations are classified by comparing the distance and near angles.3 In a divergence excess pattern the exodeviation is at least 15 prism diopters larger at distance, a basic exodeviation is about equal at both distances, and a convergence insufficiency pattern is at least 15 prism diopters larger at near.3 A simulated divergence excess pattern looks larger at distance until special tests reveal a larger near deviation hidden by persistent convergence.3 The near angle is remeasured through +3.00 D lenses, or after 30 to 60 minutes of occlusion of one eye, to separate the simulated form from the true form.2
Sources (7)
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 8
- Kanski, Clinical Ophthalmology (2024), ch. 18
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 17
- American Academy of Ophthalmology. 2020. Strabismus Terminology. [online] Available at: <https://www.aao.org/education/bcscsnippetdetail.aspx?id=ce9b9c03-0bc8-4a63-8e51-09334c399fd7> [Accessed 6 May 2024].
- Noorden, G.K. and Campos, E.C. 2002. Binocular vision and ocular motility: theory and management of strabismus. 6th ed. St. Louis: Mosby.
- Rutstein, R. and Daum, K. 1997. Anomalies of Binocular Vision: Diagnosis & Management. St. Louis: Mosby.
- Von Noorden, G.K. and Campos, E.C. 2002. Binocular vision and ocular motility: theory and management of strabismus. 6th ed. St. Louis: Mosby.
Reviewed October 2026