If Strabismus Surgery Is Delayed, Can It Still Be Treated?

Strabismus surgery to correct eye alignment can still be performed in adulthood. The Korea Disease Control and Prevention Agency (KDCA) separately describes surgery in adults for strabismus that was not treated during childhood or for residual strabismus following previous surgery.¹ What becomes difficult to regain after the optimal treatment period has passed is not the eye position itself. Rather, it is the ability to use both eyes together to perceive a single image and judge depth, which is generally established between 8 and 10 years of age.¹

Therefore, the answer to this question has two aspects. There is essentially no strict age limit for correcting the appearance and alignment of the eyes, whereas there is a limited window for preserving and developing visual function.¹

A question such as the following is sometimes posted on Naver Knowledge iN:

“I feel that my symptoms are gradually getting worse. I would like to know whether there are cases in which strabismus can no longer be treated because the optimal timing for surgery was missed.”

What Exactly Is Strabismus?

Strabismus is a condition in which the two eyes are not properly aligned in the same direction.¹ One eye looks directly at the object of interest while the other eye is directed elsewhere.¹ The condition is named according to the direction in which the eye deviates. When the eye turns inward, it is called esotropia; when it turns outward, exotropia; when it turns upward, hypertropia; and when it turns downward, hypotropia.¹

Strabismus does not necessarily mean that an eye is constantly misaligned.¹ An eye that normally deviates may occasionally look straight ahead, while the eye that was previously aligned may become the deviating eye.¹

Strabismus occurs in approximately 2–3% of the general population.¹ In a study of 9,054 Korean schoolchildren, 322 children (3.56%) had strabismus.¹ The distribution of strabismus types in Korea also differs from that typically reported in Western populations.¹ In the same study, among the 322 children with strabismus, 262 (81.4%) had exotropia and 60 (18.6%) had esotropia.¹

Why Is Early Detection So Important?

This is because visual acuity and the ability to use both eyes together develop and mature during childhood, generally reaching maturity around 8–10 years of age.¹ The KDCA notes that strabismus occurring before age 8 can result in significant visual impairment and damage to visual function if left untreated.¹

When strabismus affects only one eye, the child may gradually stop using that eye.¹ The visual acuity of an eye that is not adequately used may fail to develop normally, resulting in amblyopia, commonly known as “lazy eye.”

Amblyopia refers to reduced visual acuity that cannot be corrected to normal levels even with appropriate glasses.¹ The term is generally used when there is a difference of at least two lines in visual acuity between the two eyes and no structural or neurological abnormality of the eye can explain the difference.¹

Amblyopia caused by strabismus occurs primarily in cases of strabismus that develop during early childhood.¹ It is particularly common in infantile esotropia and accommodative esotropia, whereas its incidence is relatively low in intermittent exotropia.¹

The ability to use both eyes together is also affected.¹ Without treatment, binocular vision and stereopsis (depth perception) may fail to develop normally. When strabismus is present from shortly after birth, the cells in the visual cortex responsible for binocular vision may also undergo abnormal development or atrophy.¹

Does the Urgency of Treatment Differ Depending on the Type of Strabismus?

Yes. Recommendations can differ substantially depending on the type of strabismus. The KDCA provides the following guidance regarding timing.¹

Type	Recommendation regarding timing
Infantile esotropia	Surgery can be performed from approximately 4–5 months of age and is generally recommended no later than age 2
Infantile exotropia	Surgery can be performed from approximately 4–5 months of age and is generally recommended no later than age 2
Accommodative esotropia	Correction of hyperopia with appropriate glasses is the primary treatment
Intermittent exotropia	Timing is determined based on the frequency of deviation, stereopsis, and the angle of deviation
Adult strabismus	Surgery may be performed to relieve symptoms such as diplopia

Infantile esotropia refers to esotropia that develops within the first six months of life. It is usually associated with a large angle of deviation, often greater than 30 prism diopters, and occurs in approximately 0.1–1% of the general population.

There is a reason for the recommendation to treat it before age 2. Binocular visual function develops rapidly from approximately 2–6 months of age through 1–2 years of age. If this ability does not become established during this critical period, normal stereopsis may not develop.

Infantile esotropia often cannot be completely resolved with a single operation. Even when the esotropia is successfully corrected, another type of strabismus may develop around age 3–4. Repeat surgery may therefore be required in some children.

Follow-up remains important even after surgery. Children with infantile esotropia remain at increased risk of developing amblyopia after surgery. Regular examinations, typically at least every six months, are recommended, with monitoring continuing through approximately 8–10 years of age, when visual acuity and visual function become more fully established.

Does Intermittent Exotropia Get Worse If It Is Left Untreated?

In one study that observed children with intermittent exotropia without treatment for three years, 15% were classified as having worsened. The study followed 183 previously untreated children between 3 and 10 years of age with intermittent exotropia.

Intermittent exotropia is a condition in which one or both eyes intermittently turn outward. It may become more noticeable when a child is tired, upon waking in the morning, when febrile, or when staring blankly.

However, the authors provided an important qualification regarding the reported 15% figure. They stated that the rate may have been overestimated because of factors such as misclassification.

The details of the 25 cases classified as having worsened help explain this. Only two cases involved an actual deterioration in eye alignment. Eleven involved worsening stereopsis, while 12 children began treatment even though they met neither of the two predefined criteria for deterioration. Of those 12 children, seven began treatment because of social concerns, one because of diplopia, and four for other reasons.

The results among children who completed the full three-year observation period were even more reassuring. Of the 132 children who remained untreated through the three-year visit, only one met the study's criteria for deterioration at three years—less than 1%.

On average, these 132 children actually showed improvement. Distance and near stereopsis, the ability to maintain ocular alignment at distance, and the angle of deviation all improved compared with baseline.

However, these findings apply specifically to children aged 3–10 years with intermittent exotropia. They should not be directly extrapolated to conditions such as infantile esotropia or paralytic strabismus.

Does Earlier Surgery Always Lead to Better Results?

One analysis found that younger age at surgery was associated with better outcomes in children with intermittent exotropia. The analysis included 197 children aged 3 to under 11 years with basic-type intermittent exotropia and deviation angles of 15–40 prism diopters.

The proportion of children with an unsatisfactory surgical outcome within three years differed according to age. Among children aged 3 to under 5 years, 19 of 72 (28%) had an unsatisfactory outcome, compared with 57 of 125 (50%) among children aged 5 to under 11 years.

Other factors were not significantly associated with outcome. The magnitude of the deviation, distance control score, preferred eye, and near stereopsis were not statistically significantly associated with an unsatisfactory result.³

An important limitation should be emphasized: this was a secondary analysis of data from randomized trials, rather than a randomized trial directly comparing immediate surgery with delayed surgery. Further direct evidence would therefore be needed to establish whether earlier surgery itself produces better outcomes.³

Are There Effective Alternatives to Surgery?

Patching therapy improved ocular alignment compared with observation alone. This conclusion comes from a Cochrane review that included six randomized controlled trials involving 890 participants.⁴

In a meta-analysis of two studies comparing 249 children who received patching with 252 who were observed, ocular alignment at six months was better with patching for both near and distance measurements. The certainty of evidence for this outcome was rated as high.⁴

Stereopsis, however, showed a different pattern. There was little or no difference between patching and observation in near stereopsis, and the certainty of evidence for this outcome was low.⁴

The KDCA also notes limitations to nonsurgical treatment for intermittent exotropia. Options include correction of refractive errors, overcorrecting minus lenses, vision therapy, and patching, but their effectiveness may be limited.¹

A Cochrane review has also compared botulinum toxin injections with surgery.⁵ Based on four randomized controlled trials involving 242 participants, surgery may have been more likely to successfully correct strabismus, although the certainty of evidence was low. None of the studies included in the review had a low risk of bias across all assessed domains.⁵

In other words, the comparative evidence regarding different strabismus treatments is still limited.

How Can Parents Tell at Home Whether Their Child May Have Strabismus?

Some forms of strabismus may not be readily apparent during a clinical examination, making parental observation important. The KDCA lists the following clues that may suggest strabismus:¹

1. The child closes one eye in bright sunlight.

2. One eye appears abnormal when the child is staring blankly.

3. The child has difficulty maintaining proper focus.

4. The child turns or tilts the head when looking at an object.

Conversely, an appearance that resembles strabismus does not always indicate true strabismus. Asian children may have a relatively broad nasal bridge, a lower nasal bridge, epicanthal folds, and smaller-appearing eyes. As a result, the white part of the eye on the nasal side may be partially covered by the eyelid, making the eyes appear to turn inward.¹ This is known as pseudostrabismus, specifically pseudoesotropia.¹

As the child grows, facial contours change and the nasal bridge becomes more prominent, exposing the previously hidden sclera and causing the appearance of crossed eyes to disappear.

It is also worth noting that many children with intermittent exotropia do not complain of discomfort themselves. A suppression mechanism may develop that allows the brain to ignore visual information from the deviating eye, preventing the child from experiencing double vision.

What Does It Mean If an Adult Develops Strabismus Suddenly?

The most characteristic symptom of newly acquired strabismus in adults is diplopia (double vision). Children can rapidly develop suppression mechanisms that prevent diplopia from becoming noticeable, whereas adults generally do not adapt in the same way.

In some cases, the underlying cause is outside the eye itself. Possible causes include thyroid dysfunction, paralytic strabismus caused by cranial nerve injury, trauma around the eye, and ischemic nerve damage associated with diabetes or hypertension.

For this reason, the diagnostic evaluation may need to be broader. When paralytic strabismus or an associated systemic disorder is suspected, additional investigations such as CT, MRI, or blood tests may be necessary.

Superior oblique palsy is one of the most common forms of paralytic strabismus. The superior oblique is one of the six extraocular muscles that control eye movement. Problems involving the muscle itself or the trochlear nerve (cranial nerve IV) that innervates it can cause this condition.

Patients commonly tilt their head away from the affected side. If this abnormal head posture persists for a long time, facial asymmetry may develop.

What Does Strabismus Surgery Do, and What Problems Can Remain?

Strabismus surgery adjusts the position of the muscles that move the eyes, either weakening or strengthening their effects. The six extraocular muscles are the medial rectus, lateral rectus, superior rectus, inferior rectus, superior oblique, and inferior oblique muscles.

The number and type of muscles operated on are determined according to the angle and type of strabismus.

Surgery performed on either the healthy eye or the deviating eye can produce similar effects in appropriate cases.

Adults have different anesthesia options. In some cases, an adjustable-suture technique allows the eye position to be assessed while the patient is awake after surgery and the muscle position adjusted accordingly. This may reduce the need for additional surgery, although it does not guarantee a better outcome in every case.

Strabismus surgery in children is generally performed under general anesthesia.¹ The choice between general and local anesthesia depends on factors such as the patient's age, pain, and the complexity of the procedure.

The KDCA describes the following potential postoperative problems:¹

1. Diplopia may occur. Objects may appear double immediately after surgery. This usually improves with patching, but if diplopia persists for more than 1–3 months, additional surgery may sometimes be necessary.

2. Residual undercorrection may remain. If the correction is insufficient, the patient may initially be observed and repeat surgery considered if necessary.

3. Overcorrection may occur. In intermittent exotropia, temporary overcorrection can sometimes be preferable because alignment may gradually return toward normal. Rarely, if the overcorrection does not resolve, repeat surgery may be required.

4. Strabismus may recur. If ocular alignment becomes unbalanced again, recurrence can occur at any time. Children who are still growing may experience frequent changes in alignment and therefore require periodic monitoring.

5. Latent strabismus may become manifest. Previously hidden strabismus may become apparent after surgery.

6. Infection may occur. For approximately 1–2 months after surgery, care should be taken to prevent water or hands from coming into contact with the surgical wound.

7. Scleral perforation may occur. This involves injury to the sclera, the thin tissue forming the white part of the eye. In rare cases, laser treatment may be required.

8. Complications related to general anesthesia may occur.

So, When Should My Child Be Evaluated?

The first step is to determine the type of strabismus. Some forms, such as infantile esotropia, have a recommended treatment window before age 2, while others, such as intermittent exotropia, may not worsen in most children even after three years of observation.¹˒²

The distinction between these conditions is made through a comprehensive eye examination. An ophthalmologist may use the prism alternate cover test, cover and uncover tests, and other alignment assessments to determine the frequency and angle of deviation. Cycloplegic refraction and a fundus examination may also be performed to evaluate refractive errors and rule out other ocular conditions.¹

Some forms of strabismus can be managed primarily by correcting refractive errors.¹ For example, in accommodative esotropia, in which hyperopia causes the eyes to turn inward, prescribing glasses that fully correct the hyperopia can eliminate the strabismus in many cases.¹

A child's emotional well-being is another consideration.¹ Not every child with strabismus experiences psychological difficulties, but strabismus has been associated with a somewhat increased risk of emotional and behavioral problems, including lower self-esteem, anxiety, depression, and attention-deficit/hyperactivity disorder (ADHD).¹

After determining the child's specific type of strabismus and ocular condition, the timing and type of treatment should be decided in consultation with an ophthalmologist.

Sources

1. Korea Disease Control and Prevention Agency (KDCA), National Health Information Portal. Strabismus.

2. Pediatric Eye Disease Investigator Group; Mohney BG, Cotter SA, Chandler DL, et al. Three-Year Observation of Children 3 to 10 Years of Age with Untreated Intermittent Exotropia. Ophthalmology. 2019;126(9):1249–1260.

3. Repka MX, Chandler DL, Holmes JM, et al. The Relationship of Age and Other Baseline Factors to Outcome of Initial Surgery for Intermittent Exotropia. American Journal of Ophthalmology. 2020;212:153–163.

4. Pang Y, Gnanaraj L, Gayleard J, et al. Interventions for intermittent exotropia. Cochrane Database of Systematic Reviews. 2021;9:CD003737.

5. Bort-Martí AR, Rowe FJ, Ruiz Sifre L, et al. Botulinum toxin for the treatment of strabismus. Cochrane Database of Systematic Reviews. 2023;3:CD006499.

This article provides general information based on publicly available materials from the Korea Disease Control and Prevention Agency, Cochrane reviews, and peer-reviewed academic literature. It is not a substitute for an individualized examination or medical advice from an ophthalmologist.