Parents often first notice the problem in a photograph. One eye may appear to look directly at the camera while the other turns inward, outward, upward, or downward. Parents may understandably be concerned and ask, ‘Doctor, it only happens some of the time. Could it be nothing? In some cases, the misalignment is so subtle that only a trained eye can detect it. Strabismus, also known as crossed eyes or squint, is a condition in which the eyes do not point in the same direction at the same time. It is not just a cosmetic issue. If left untreated it can affect how the brain learns to use both eyes as a team and may cause amblyopia also known as lazy eye. The good news is that strabismus is one of the most treatable conditions in pediatric eye care and does so much better when caught early.
What Is Strabismus?
In a normal visual system, both eyes focus on the same object at the same time.The brain receives two slightly different images – one from each eye and combines them into a single three-dimensional image.
That is what we call binocular vision. In strabismus, the eyes are out of alignment. It may be that one eye is looking at the object of focus and the other is looking off in another direction. The brain receives two very different images that do not fuse.
In children the brain often suppresses the input from the misaligned eye to avoid confusion in the process that eye’s development for normal vision is impaired. This is how amblyopia develops. In adults with strabismus, double vision is more common because the visual system is fully developed and the brain cannot easily suppress input from one eye.
Types of Strabismus
Strabismus is classified by the direction of the deviation and by how consistently it is present.
| Type | Direction of deviation | Common names used |
| Esotropia | Eye turns inward toward the nose | Convergent squint, crossed eyes |
| Exotropia | Eye turns outward away from the nose | Divergent squint, wall-eye |
| Hypertropia | Eye turns upward | Vertical squint |
| Hypotropia | Eye turns downward | Vertical squint |
| Intermittent | Deviation present only at times, not constantly | Intermittent exotropia is the most common form in children |
| Constant | Deviation present at all times | May indicate longer-standing or more significant misalignment |
Esotropia is the most common form seen in young children in India. Intermittent exotropia, in which one eye drifts outward, particularly when the child is tired, daydreaming, or looking into the distance, is also commonly seen.
What Causes Strabismus?
Strabismus does not have a single cause. It can arise from problems in the eye itself, the muscles, the nerves, or the brain’s control of eye movement.
| Cause group | Examples |
| Refractive error | Uncorrected hyperopia (far-sightedness) is the most common cause of accommodative esotropia in children. The extra focusing effort pulls the eyes inward. |
| Muscle imbalance | Weakness or overaction of one or more of the six extraocular muscles that move each eye. |
| Neurological causes | Problems in the cranial nerves (III, IV, or VI) that control eye movement; brain lesions; raised intracranial pressure. |
| Amblyopia (lazy eye) | Poor vision in one eye from any cause can lead to that eye drifting over time. |
| Systemic conditions | Down syndrome, cerebral palsy, premature birth, and other developmental conditions are associated with higher rates of strabismus. |
| Family history | Strabismus runs in families; a parent or sibling with squint increases the child’s risk. |
| Trauma or illness | Acquired strabismus in older children or adults can follow head injury, stroke, thyroid eye disease, or other systemic illness. |
In many cases, particularly in young children, no single cause is identified. What matters most is early detection and intervention, regardless of cause.
Symptoms: What to Look For
In young children, strabismus may not cause obvious symptoms because the brain often compensates for the misalignment.It is usually parents and caregivers that are first to see there is an issue.
Signs may include:
- One eye turning inward, outward, upward, or downward, particularly in photographs.
- Closing one eye or squinting in bright sunlight, especially in cases of intermittent exotropia.
- Tilting or turning the head to improve eye alignment.
- Complaints of double vision in older children.
- Poor depth perception or difficulty judging distances.
- An eye that drifts when the child is tired, ill, or daydreaming.
- Adults with strabismus commonly report double vision, which can interfere with driving, reading, and work-related activities.
Strabismus and Amblyopia: Why Timing Matters
The visual system develops rapidly during the first few years of life and continues to mature until approximately 7 to 9 years of age. During this period, the brain learns to use both eyes together as a coordinated team.If strabismus causes the brain to suppress input from one eye, the visual pathways associated with that eye may not develop normally. This can lead to amblyopia (lazy eye), which may become permanent if left untreated. Early diagnosis and treatment provide the best opportunity for the development of normal binocular vision and depth perception. Although treatment remains beneficial in older children, correcting amblyopia becomes more challenging after the age of 9 or 10.
How Is Strabismus Diagnosed?
Diagnosis involves a structured eye examination by a paediatric ophthalmologist or strabismus specialist. Several tests are used together to understand the type, size, and underlying cause of the deviation.
| Assessment | What it evaluates |
| Cover and cover-uncover test | Detects misalignment and whether it is constant or intermittent |
| Prism bar measurement (prism cover test) | Quantifies the degree of deviation in prism dioptres |
| Cycloplegic refraction | Measures the refractive error under dilating drops to reveal the true spectacle power, especially important for accommodative esotropia |
| Visual acuity in each eye | Identifies amblyopia by testing each eye separately |
| Ocular motility assessment | Checks the movement and coordination of both eyes in all directions |
| Binocular vision and stereopsis tests | Evaluates depth perception and how well the two eyes work together |
| Fundus examination | Rules out retinal or optic nerve problems contributing to poor vision or misalignment |
A thorough assessment at a specialised squint clinic is important because the treatment plan depends heavily on the exact type, cause, and degree of misalignment, not just whether the eyes “look crossed.”
Strabismus Treatment Options
The goal of strabismus treatment is threefold: restore the best possible vision in each eye, align the eyes as closely as possible, and develop or preserve binocular vision and depth perception. Most cases require more than one approach, used together in a planned sequence.
Glasses and Optical Correction
For that which is called accommodative esotropia in which uncorrected farsightedness causes the in turning we see that correction of the refractive error with glasses often does what is required to straighten the eyes back out which in some cases is the only treatment that is needed.
Also we put to use bifocal glasses in a select group of children in which the in turn is more noticeable for near tasks. Very much a part of the care plan is regular review which is because the prescription changes as the child grows and also the degree of accommodative deviation may also change over time.
Patching and Amblyopia Treatment
If amblyopia is present in the misaligned or weaker eye, it must be treated alongside the strabismus. Patching the stronger eye forces the weaker eye to work, stimulating the development of its visual pathways.
Patching is most effective during the sensitive period of visual development ideally before age seven to eight. Atropine drops in the stronger eye are an alternative to patching in some children. Compliance is important; consistent patching as prescribed by the doctor makes a real difference to the final visual outcome.
Strabismus Surgery
In some cases when glasses are not sufficient for eye alignment or if the strabismus is mainly structural in origin, we turn to eye muscle surgery. Strabismus surgery consists of repositioning and adjusting one or more of the extraocular muscles, which in turn changes the alignment of the eye. In children the procedure is done under general anesthetic and in adults it is usually done under local or general anesthetic. It is a day procedure to have both eyes done at the same time when both require it. We cannot count on perfect alignment with a single procedure; some patients may require a second operation. The goal is to achieve as much alignment as is practical for the brain to use both eyes together, which may not be perfect cosmetic alignment.
Botulinum Toxin Injection
In some cases, especially for smaller angle issues, temporary palsy conditions, or when surgery is at high risk we see use of botulinum toxin injected into the overacting muscle. This weakens the muscle which in turn may allow the brain to recover some binocularity. It is not a permanent fix in most cases but does play a large role in certain situations.
Vision Therapy
For intermittent exotropia and certain types of convergence weakness, structured vision therapy exercises can improve the brain’s ability to keep the eyes aligned, particularly for near tasks. This is most useful as an adjunct to other treatments rather than a standalone cure for most forms of strabismus.
Strabismus (Squint Eye) Treatment at Vasan Eye Care
At Vasan Eye Care we have pediatric ophthalmologists and strabismus specialists which evaluate each child and adult patient with a structured exam before putting forth any treatment plan. In India at specialized centers like Vasan we have individualized treatment plans which include the use of glasses and amblyopia therapy as the first line of treatment and we supplement that with surgical correction when needed. We also perform squint eye treatment in adults, which includes cases that are acquired post stroke, from thyroid eye disease, or from past trauma. For adults with long term strabismus which desire better alignment and cosmetic results we evaluate based on the stability of the deviation and the visual potential of each eye. Post op follow up is a structured series of visits to monitor alignment, manage amblyopia if present, and to assess binocular vision recovery. We guide families at every step what to expect and how to support the child’s visual development at home.
Key Takeaways
Strabismus is a condition in which the eyes are misaligned so they do not focus in the same direction at the same time. It affects people of all ages and has many causes which include uncorrected refractive error, muscle imbalance, and neurological factors.
Early diagnosis and treatment is key as in young children, strabismus may cause amblyopia, a reduction in the vision of the affected eye if left untreated through the sensitive period of visual development.
Treatment includes the use of glasses for refractive error, patching for amblyopia, and surgery for muscle misalignment that does not respond to corrective lenses.
Also it is very much an individual approach. In India at experienced centers, we see very good results for squint eye treatment which is also true that the earlier the treatment is started and the more consistent it is the better the outcome.
Frequently Asked Questions
Treatment is based on the type and cause of strabismus. In the case of accommodative esotropia many children respond to correction with glasses. Should amblyopia be present we add patching of the dominant eye. At times when glasses and patching do not suffice or the strabismus is not of an optical nature, eye muscle surgery is recommended. Most patients do better with a planned sequence of these treatments as opposed to a single approach.
In in young age groups the most common cause is uncorrected hyperopia far sightedness which causes extra focusing effort that pulls the eyes in. Muscle imbalance, neurological conditions, amblyopia, and a family history of strabismus are also other key causes. In adults onset of strabismus is more often a result of nerve palsy, thyroid eye disease, stroke, or trauma. A full exam is required to determine the exact cause in each case.
When we see that strabismus is a result of refractive error it is treated with the use of glasses at times bifocal which in many cases fully correct the misalignment without the need for surgery. For amblyopia we use patching which also at times improves alignment as the poorer eye’s vision improves. We see vision therapy to be useful in certain types of intermittent strabismus. But when the misalignment is large, constant, or not a result of refractive error surgery is usually required to achieve the best results.
In the case of accommodative esotropia we see that which is often a result of refractive errors, in many instances we may correct the issue with glasses which in turn may bring the eyes back to a normal position while the child is wearing them. As for other types of strabismus, we may have success in greatly improving or fully correcting the misalignment but in this we also see that for the most part it requires surgical intervention. Following successful treatment most kids do well in terms of maintaining good eye alignment and also as regards to the development of binocular vision especially if treatment is begun during the sensitive period of visual development.
References
- Cleveland Clinic – Strabismus (Crossed Eyes)
https://my.clevelandclinic.org/health/diseases/strabismus-eye-misalignment - American Optometric – Strabismus
https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/strabismus