Childhood strabismus: surgery, glasses or vision training?

By Crystal Wong 王水晶, Registered Optometrist (Part I), Hong Kong｜July 2026

What is strabismus, and why treat it early?

Strabismus (commonly known as a "squint" or "crossed eyes") means the two eyes cannot aim at the same target at the same time — one eye fixates on the target while the other turns inward, outward, upward or downward. Strabismus does more than affect appearance: during the period of visual development, the brain may "suppress" the image from the deviating eye to avoid double vision, and over time this can lead to poor visual development in that eye, resulting in amblyopia. It also affects stereopsis (depth perception). The earlier strabismus is detected and treated, the better the binocular visual function that can be preserved.

Common types of childhood strabismus

• Esotropia (eso): the eye turns inward. Some cases are "accommodative esotropia," which is related to the degree of hyperopia and may improve markedly once the correct glasses are worn.
• Exotropia (exo): the eye turns outward; many cases are "intermittent," appearing only when the child is tired, daydreaming or unwell.
• Hyper-/hypotropia (hyper/hypo): vertical misalignment, which is less common.
• By time of onset, strabismus is divided into congenital and acquired; by how stable it is, into constant and intermittent.

Treatment strategies differ greatly between the various types of strabismus — so hearing the word "strabismus" should not lead anyone to assume that surgery is inevitable. For a closer look at the most common form, intermittent exotropia, see: Intermittent exotropia: 6 management options — how should parents choose?

Four main treatment methods

1. Corrective glasses (sometimes with a prism)

If the strabismus is related to refractive error (the most typical being accommodative esotropia accompanied by hyperopia), an accurate glasses prescription may markedly improve the eye alignment, and may even avoid the need for surgery. For certain small-angle or vertical strabismus, a prism can be incorporated into the lenses to help align the images from the two eyes and reduce double vision.

2. Patching (to treat accompanying amblyopia)

If the strabismus has already caused amblyopia in the deviating eye, patching (covering the better-seeing eye to force the amblyopic eye to "work") is an important step in building up vision. Note that patching treats the amblyopia, not the eye alignment directly — the two have different aims, and patching often needs to be combined with other methods.

3. Vision training (binocular coordination and convergence)

The area with stronger evidence for vision therapy is convergence insufficiency — a large randomised controlled trial (CITT) showed that in-office training combined with home practice has a clear benefit for children with convergence insufficiency¹. For some cases of intermittent exotropia, or cases where fusion or stereopsis problems remain after surgery, vision therapy can help build binocular coordination. However, vision therapy cannot "straighten" a large-angle constant strabismus — such cases usually require surgery.

4. Strabismus surgery

When the angle of misalignment is larger, or when neither glasses nor training can align the eyes, the ophthalmologist may consider strabismus surgery, adjusting the position or tension of the extraocular muscles to improve alignment. It must be stressed that surgery corrects the "eye alignment," but does not necessarily also restore "binocular coordination" — so some children still need to be assessed after surgery for whether vision therapy is required. I have a separate article covering this in detail: Is vision training still needed after strabismus surgery?

How is the right method decided?

There is no universal formula. Before deciding on a treatment plan, a detailed assessment is needed to establish: the type and angle of the strabismus, whether it is constant or intermittent, whether there is accompanying refractive error or amblyopia, and the current state of stereopsis and fusion. The ophthalmologist and optometrist then decide, based on the assessment findings, whether to use a single method or a combination, and in what order. This assessment overlaps to a large extent with a children's binocular vision assessment.

Signs for parents to watch for

1. Noticing that one of your child's eyes sometimes, or often, "drifts" inward or outward
2. Tilting the head, squinting, or covering one eye to see comfortably
3. Eye misalignment that is especially noticeable when tired, unwell or daydreaming
4. Poor judgement of distance when catching a ball or going down stairs; complaints of double vision
5. A family history of strabismus, amblyopia or high hyperopia

If any of the above appears, arranging a comprehensive examination is advisable — the earlier it is detected, the more options are available and the better the outcome.

Crystal Wong 王水晶

Registered Optometrist (Part I), Hong Kong; BSc (Hons) in Optometry, The Hong Kong Polytechnic University; doctoral researcher in visual neuroscience. Seven years of clinical and research experience, having co-managed childhood strabismus, amblyopia and post-operative cases alongside ophthalmologists in a multi-specialty eye clinic. Full professional profile →