What Is Strabismus?
Strabismus is a condition in which the two eyes do not point in the same direction at the same time. One eye may turn inward, outward, upward or downward relative to the other. The misalignment may be constant or intermittent, and may affect one eye predominantly or alternate between eyes.
Strabismus affects approximately 3–4% of children. It is not something a child will “grow out of” after the age of 4 months, and waiting to seek assessment can allow amblyopia to develop and become entrenched.
3–4%
Children affected by strabismus
Age 7
Upper limit of the visual critical period for amblyopia treatment
>80%
Success rate with early combined treatment
Types of Strabismus in Children
The most important distinction in childhood strabismus is between the two most common horizontal types — esotropia and exotropia:
| Esotropia (inward turn) | Exotropia (outward drift) | |
|---|---|---|
| Direction of turn | Inward (convergent) | Outward (divergent) |
| Most common presentation | Constant crossing in infantile type; crossing only when focusing in accommodative type | Often intermittent — eye drifts out when tired, daydreaming or in bright light |
| Amblyopia risk | High — suppression of deviated eye is common | Lower — eye often alternates, maintaining some use |
| Role of glasses | Often corrects accommodative esotropia partially or fully | Minus lenses may reduce frequency; less curative than in esotropia |
| Surgery timing | Infantile: before 2 years for best binocular outcome; accommodative: if glasses don't fully correct | When control deteriorates or deviation becomes constant |
Within esotropia, the two most important subtypes in children are:
- Infantile esotropia— appears before 6 months of age, is typically a large constant crossing, and is not related to the child’s refractive error. Requires surgical treatment.
- Accommodative esotropia— related to hyperopia (long-sightedness); the effort of focusing triggers excessive convergence. Glasses correcting the full hyperopic prescription often straighten the eye significantly or completely.
The Critical Link with Amblyopia
When the eyes are misaligned, the brain receives two conflicting images. To avoid double vision, the brain suppresses — or “switches off” — the image from the deviating eye. Over time, this suppression becomes permanent, and the visual pathway from that eye fails to develop normally. This is amblyopia.
Amblyopia does not resolve when the strabismus is corrected — it requires its own treatment (patching or atropine drops to force the brain to use the weaker eye). The window for amblyopia treatment is the visual critical period, which extends to approximately age 7 in most children, with diminishing effectiveness after that.
Amblyopia treatment and strabismus correction are separate
Noticed your child’s eyes crossing or drifting?
Early assessment makes a significant difference to long-term outcomes. A referral from your GP or optometrist is needed to see our paediatric ophthalmology team.
Treatment Options
Treatment depends on the type of strabismus, its cause, and whether amblyopia is present. Most children require a combination of approaches:
- Glasses— prescribed after a cycloplegic refraction (dilated eye examination). Essential for accommodative esotropia and for any significant refractive error contributing to the deviation.
- Patching or atropine— to treat amblyopia in the weaker eye by penalising the stronger eye. Usually part-time patching for 2–6 hours per day.
- Surgery— adjusts the tension of the extraocular muscles to rebalance the eye position. For infantile esotropia, surgery before 2 years of age gives the best chance of developing binocular vision. For accommodative esotropia not fully corrected by glasses, surgery addresses the residual non-accommodative component.
- Botulinum toxin— injection into an extraocular muscle can be used in some cases as an alternative to, or bridge before, surgery.
Frequently Asked Questions
Not always. Accommodative esotropia — the type related to hyperopia — often responds well to glasses alone, fully straightening the eye without surgery. However, infantile esotropia, non-accommodative deviations, and strabismus that does not fully respond to glasses typically require surgery. Your ophthalmologist can advise on the right approach after assessing the type and angle of deviation.
Written by
Dr Parth ShahDr Parth Shah is a subspecialty-trained Canberra ophthalmologist with expertise in strabismus surgery, paediatric eye care and cataract surgery.
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