# Pediatric Strabismus: Esotropia and Exotropia

## Introduction

**Strabismus** affects approximately 3-5% of children and is a leading cause of amblyopia. Early recognition and appropriate management are critical for optimal visual and binocular development. This lecture reviews the classification, evaluation, and management of the major forms of childhood esotropia and exotropia.

## Evaluation of Pediatric Strabismus

### Key Examination Elements

**Visual acuity** -- age-appropriate testing; fixation preference in preverbal children. **Cover testing** -- cover-uncover (tropia), alternating cover test (total deviation), prism cover test (quantification) **Hirschberg test** -- corneal light reflex; 1 mm displacement ~ 15 prism diopters. **Krimsky test** -- prism correction of corneal reflex displacement. **Cycloplegic refraction** -- essential to detect hyperopia in esotropia. **Sensory testing** -- stereoacuity (Titmus, Randot), Worth 4-dot, Bagolini lenses.

**Extraocular motility** -- versions and ductions; identify muscle restrictions or palsies. **Fundus examination** -- rule out organic pathology (retinoblastoma, optic nerve hypoplasia)

## Esotropia Classification Summary

| Type | Onset | Deviation | Hyperopia | Key Feature | Treatment |
|------|-------|-----------|-----------|-------------|-----------|
| Infantile (congenital) | < 6 months | Large (>30 PD), constant | Minimal | Cross-fixation, DVD, latent nystagmus | Surgery by 12 months |
| Fully accommodative | 2-3 years | Moderate | +2.00 to +6.00 D | Corrected by full hyperopic Rx | Spectacles (full cycloplegic Rx) |
| High AC/A ratio | 2-3 years | Near > distance | Variable | Esotropia at near with straight distance | Bifocals (+2.50 to +3.00 add) |
| Partially accommodative | 2-3 years | Residual with Rx | Moderate | Non-accommodative component remains | Spectacles + surgery for residual |
| Acquired non-accommodative | > 6 months | Variable | Minimal | Consider neuroimaging; acute onset = red flag | Surgery; rule out neurologic cause |
| Sensory | Any age | Variable | Variable | Secondary to unilateral vision loss | Treat underlying cause; then surgery |

## Esotropia

### Infantile (Congenital) Esotropia

Onset before age 6 months; large, constant deviation (typically >30 PD) **Features**: cross-fixation pattern, latent nystagmus, dissociated vertical deviation (DVD), inferior oblique overaction. Minimal hyperopia (not accommodative) **Treatment**: surgical correction by age 12 months for best binocular outcome (bilateral medial rectus recession) Goal: alignment within 10 PD of orthophoria. **Ciancia syndrome**: large-angle infantile esotropia with limited abduction and face turn.

### Accommodative Esotropia

**Fully accommodative**: onset typically 2-3 years; moderate-to-high hyperopia (>=+2.00 to +6.00 D); corrected with full hyperopic spectacles. **High AC/A ratio**: esotropia at near > distance; treat with bifocals (+2.50 to +3.00 add) **Partially accommodative**: residual esotropia with full correction; may need surgery for the non-accommodative component. Always prescribe full cycloplegic refraction; do not undercorrect hyperopia.

### Acquired Non-Accommodative Esotropia

Onset after 6 months without significant hyperopia. May herald neurologic disease; consider neuroimaging (MRI brain) especially with: CN VI palsy, papilledema, nystagmus. Acute-onset esotropia with diplopia in a previously aligned child. **Sensory esotropia**: secondary to unilateral vision loss (cataract, optic atrophy)

![Clinical photograph demonstrating large-angle infantile esotropia with cross-fixation](/images/ophthalmology/infantile-esotropia-cross-fixation.jpg)

## Exotropia

### Intermittent Exotropia

Most common childhood exotropia; onset typically 2-5 years. **Manifests during fatigue, inattention, illness, or bright light** (monocular eye closure in sunlight) Control assessed by Newcastle Control Score or office-based criteria. **Types** (Burian classification): Basic: equal distance and near deviation. Divergence excess: distance deviation > near by >= 10 PD (true vs. pseudo -- patch test)

Convergence insufficiency: near deviation > distance.

**Management**: Observation for well-controlled, small-angle deviations. Part-time patching of the dominant eye (3-4 hours/day) to disrupt fusion and increase awareness. Minus lens therapy (-2.00 to -3.00) to stimulate accommodative convergence. Surgery when control deteriorates, stereoacuity declines, or deviation increases. **Surgical approach**: bilateral lateral rectus recession (divergence excess) or recess-resect (basic type)

### Constant Exotropia

**Infantile exotropia**: rare; rule out neurologic disease, craniofacial abnormalities. **Consecutive exotropia**: overcorrection from prior esotropia surgery; may occur years later. **Sensory exotropia**: adults typically exotropic from unilateral vision loss.

### Convergence Insufficiency

Near deviation > distance; recedes with near point testing. **Symptoms**: asthenopia, headache, difficulty reading, loss of place. **Treatment**: office-based vergence/accommodative therapy (CITT study); base-in prisms; rarely surgery.

![Photograph showing intermittent exotropia manifesting during distance fixation in a child](/images/ophthalmology/intermittent-exotropia-distance.jpg)

## Surgical Principles

Standard surgical dose tables based on prism diopter deviation. **Adjustable sutures** -- useful in older, cooperative patients. Bilateral symmetric surgery preferred when possible (cosmetic and functional) **Complications**: undercorrection, overcorrection, scleral perforation, anterior segment ischemia (rare), lost muscle.

![Intraoperative photograph of medial rectus recession for infantile esotropia](/images/ophthalmology/medial-rectus-recession-intraop.jpg)

## Key Clinical Pearls

Always perform cycloplegic refraction in childhood esotropia -- accommodative component is common. Infantile esotropia requires early surgery; accommodative esotropia is treated with glasses first. Acute-onset esotropia in a previously well-aligned child warrants urgent neuroimaging. Intermittent exotropia surgery timing is based on deteriorating control, not deviation size alone. Convergence insufficiency responds best to office-based vergence therapy, not surgery.

## References

1. Birch EE, et al. Infantile esotropia results of treatment at age 6 versus 24 months. Ophthalmology. 2004;111(12):2076-2081.
2. Scheiman M, et al. Randomized clinical trial of the effectiveness of base-in prism reading glasses versus placebo reading glasses for symptomatic convergence insufficiency in children. Ophthalmology. 2005;112(5):795-802.
3. Hatt SR, et al. Interventions for intermittent exotropia. Cochrane Database Syst Rev. 2015;5:CD003737.
4. American Academy of Ophthalmology. Pediatric Ophthalmology and Strabismus. BCSC Section 6. 2023-2024.