Exotropia: Board Review Essentials

Master exotropia for NBEO and OKAP: types, high-yield signs, measurement and management principles.

Reviewed for accuracyJuly 27, 20263 min read

Three-panel schematic comparing ocular alignment using the Hirschberg corneal light reflex test: orthotropia with both reflexes centered and symmetric, exotropia where the deviated eye turns outward and its corneal light reflex sits nasally, and esotropia where the deviated eye turns inward and its reflex sits temporally

Warm-up

Exotropia refers to:

Lesson

Exotropia in 30 Seconds

Exotropia is an outward ocular deviation that may be intermittent or constant. Intermittent exotropia is the most common exodeviation and often appears with distance fixation, fatigue or bright light. For NBEO and OKAP, assess control, measure the deviation and identify reduced vision or another cause.

What Exotropia Is

Exotropia is a manifest outward (temporal) deviation of one eye relative to the fixing eye, although fixation may alternate between eyes. Exophoria is latent and controlled by fusion during normal binocular viewing. Exotropia is manifest. Esotropia differs because the eye deviates nasally rather than temporally. The eyes are moved by the extraocular muscles, whose balance determines ocular alignment.

Types of Exotropia

Intermittent exotropia: The most common type. Control, frequency and distance versus near findings guide management. The deviation is commonly larger at distance than at near.
Constant exotropia: The deviation remains manifest and may indicate poorer binocular function.
Infantile (congenital) exotropia: Presents within the first 6 months of life and is typically large-angle and constant.
Sensory exotropia: Poor vision in one eye disrupts fusion, allowing that eye to drift outward.
Consecutive exotropia: An exodeviation that develops after prior treatment, often surgery, for esotropia.
Exotropia in Duane syndrome type 2: Limited adduction from congenital cranial dysinnervation can produce a primary-position exodeviation.

4 Facts Exams Always Ask

Intermittent exotropia is the most common type. It often worsens with fatigue, illness, bright light or distance fixation, and is commonly greater at distance than at near.
Sensory exotropia signals monocular visual impairment. Investigate and treat a reversible cause of reduced vision when possible.
Measure the deviation using the alternate prism cover test at distance and near. Control is graded by how often the exotropia is manifest and how quickly fusion is regained after dissociation.
Observation is reasonable when control and binocular function remain stable. Consider surgery when the deviation becomes frequent or constant, or when symptomatic diplopia, asthenopia or loss of binocular vision develops.

The Classic Trap

Do not dismiss an exotropia as cosmetic. A sensory exotropia may reveal significant monocular vision loss, while an acquired deviation requires a careful motility and ocular evaluation. New-onset exotropia accompanied by diplopia or neurologic symptoms warrants evaluation for neurologic causes. First determine whether the deviation is intermittent or constant, assess visual acuity and look for an underlying cause. Patients with longstanding exotropia may suppress the deviated eye to avoid diplopia, and amblyopia is less common in alternating intermittent exotropia than in constant unilateral strabismus.

Clinical Pearl

A child who closes one eye in bright sunlight may have intermittent exotropia. This behavior is a useful history clue, especially when alignment appears normal during a brief office examination.

Check yourself

Checkpoint 1

The alternate cover test is most useful for measuring the:

Checkpoint 2

Sensory strabismus most often develops because of:

Clinical case

A patient with intermittent exotropia is measured on alternate prism cover testing. The exodeviation is significantly larger at distance than at near. After one eye is patched for one hour, the near measurement remains normal and the distance deviation stays significantly larger than the near.

A patient with intermittent exotropia that is significantly larger at distance than near, with normal near measurements after patching one eye for one hour, most likely has which type?

Explanation

True divergence excess exotropia maintains a significantly larger distance deviation than near deviation even after monocular occlusion for an hour (the patch test), which distinguishes it from simulated divergence excess where the near deviation increases to match the distance deviation once fusional convergence is disrupted by patching. This distinction is critical for accurate surgical planning.

Case discussion

The deviation is significantly larger at distance than at near, which raises the question of divergence excess. Patching one eye for one hour dissociates the eyes and unmasks any latent near deviation. Because the near measurement stays normal and the distance deviation remains significantly larger even after patching, this is true divergence excess rather than a simulated (pseudo) divergence excess pattern, where the near deviation would increase to match the distance after prolonged monocular occlusion.

Sources & Reviewer Info

Reviewed by Vasilis Inglezis: Optometrist and Ocular Oncology Imaging Specialist, Ocular Oncology Center, Athens, Greece. Last updated July 27, 2026.

Diagram created with AI image generation, clinically reviewed for accuracy.

References

American Academy of Ophthalmology. Basic and Clinical Science Course, Section 6: Pediatric Ophthalmology and Strabismus.
American Association for Pediatric Ophthalmology and Strabismus. "Exotropia."
American Academy of Ophthalmology EyeWiki. "Exotropia."

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