What is squint (strabismus)?

Squint is a mis-alignment of the two eyes where in two eyes are not looking in the same direction. This misalignment may be constant, being present throughout the day, or it may appear sometimes and the rest of the time the eyes may be straight called as intermittent squint

What causes squint?

The exact cause of squint is not known. Six muscles control the movement of each eye. Each of these muscle acts along with its fellow in the other eye to keep both the eyes aligned properly. A loss of coordination between the muscles of the two eyes leads to misalignment

Refractive error -hypermetropia (far sightedness) or an eye muscle paralysis may lead to deviation of the eye. Poor vision in an eye because of some other eye disease like cataract, etc. may also cause the eye to deviate.

Any trauma or injury to eye can lead to squinting of eyes .

Therefore it is important in all the cases of squint, especially in children, to have a thorough eye checkup to rule out any other cause of loss of vision.

What are the symptoms of squint?

In a child, the parents may notice the deviation of eyes.Adults may notice double vision, or misalignment of the eyes.


An esotropia is the medical name for a convergent squint where one eye turns in towards the nose.


An exotropia is the medical name for a divergent squint where the one eye turns outwards.

Hypertropias and Hypotropias

These terms refer to vertical squints where one eye is higher (hypertropia) or lower (hypotropia) than the fellow eye. There are a number of different types of squint in each of these three groups, which have their own individual characteristics and treatments.

Paralytic Squints

There are three nerves which send signals to the six eye muscles, these are the third, fourth and sixth cranial nerves. Damage to these nerves as result of poor blood supply to the nerve, pressure on the nerve or head injuries will cause limited eye movements and a squint.

How is squint diagnosed?

The squint is diagnosed by the ophthalmologist by special tests performed in squint clinic to confirm the presence of squint, and find out the type of squint.

In some cases there may be a false appearance of squint due to broad nasal bridge in a child. This is called as false squint.

When should the squint be treated?

In a child, the treatment of squint should be started as soon as possible to prevent amblyopia. The younger the age at which amblyopia is treated; the better is the chance of recovery of vision.

A delay in treatment may decrease the chances of getting a good alignment of the eyes and the vision.

What are the treatment options?


Patching/occlusion therapy

Penalisation ( which induces dilation of pupil relieves ciliary muscle spasm)


Can glasses correct squint?

If the child has developed squint due to refractive error. Wearing glasses may correct squint. This clear vision is very to prevent amblyopia, and maintaining the alignment of eyes after they have been aligned by surgery

Can yoga or exercise correct squint ?

No, yoga or general body exercise will not correct squint .there are special eye exercise offered by orthoptics clinic to relieve eye strain, headache symptoms and treat squint to certain extent.

Is surgery required to correct squint?

Treatment of squint generally requires eye muscle surgery. However, some patients may need glasses, prisms, medications, or may be best left untreated. Your ophthalmologist will decide whether u require a surgery or not.

What is amblyopia?

Amblyopia is the medical term for a “lazy eye”. The reduced vision in an amblyopic eye occurs even though there is no structural abnormality of the eye. Amblyopia is responsible for more visual loss in childhood than all the other causes of visual loss combined.

What are the causes of amblyopia?

Squints (strabismus)

When a child develops a squint their brain is able to ‘turn off’ the image from one eye, preventing them from experiencing double vision. This process is known as suppression. As a consequence of suppressing the image from one eye the connections between this eye and the brain do not develop in the normal way and the vision in this eye is reduced. This is known as strabismic amblyopia, because it has arisen as a result of a squint.

This type of amblyopia is more commonly seen in children with an esotropia (convergent squint) compared to children who have an exotropia known as divergent squint.

High Refractive error in both eyes.

Both eyes may be significantly longsighted and or one or both eyes may have a high degree of astigmatism. These conditions can result in amblyopia because of the blurred image they produce.

Unequal refractive error

The other common cause of amblyopia is when one eye is more long sighted, or (less commonly) short sighted than the fellow eye. The medical term for this unequal refractive error is anisometropia. This means that the more long or short sighted eye will be seeing a blurred image, compared to the fellow eye and the brain will choose to ignore this blurred image. In children with an esotropia their amblyopia is often due to a combination of their squint and unequal refractive error.

Deprivation amblyopia

Deprivation amblyopia is caused by anything that deprives a child’s eye of visual experience. Causes of deprivation amblyopia include cataracts (cloudy lens) and a droopy eyelid (known as a ptosis).

Why is it important to improve the vision in the amblyopic eye?

In children who have the potential to develop stereopsis, their 3D vision will be better if they have good vision in both eyes. Perhaps the most important reason for treating amblyopia is to ensure that the vision is good enough in the amblyopic eye to enable the person to drive a car, work and live independently if they were to loose the vision in their other eye in later life.

What is patching/occlusion therapy?

Squinting eye can become ‘lazy’ and result in reduced vision. Patching the ‘good’ eye will make the lazy eye work harder, which improves vision .

Patching does not treat the squint, although the unpatched eye will appear to be straight while the patch is worn when the patch is removed the squint returns to the pre-patching position. The patch is made from non-irritating material to prevent rashes, and spectacles are worn over the patch.

Why can’t I leave the patching until my child is older and I can reason with him/her?

Unfortunately by this time it is often "too late" for the patching to work. Vision is developing at its fastest rate in the early years of life.

I don’t want to do this to my child. It feels cruel?

It is also cruel to deprive them of the possibility of better vision in their weak eye. An untreated squinting eye can lead to a virtually "blind" eye.

This has consequences if the child should lose the sight of their good eye later in life through accident or eye disease.

Why can’t my child have an operation to improve the sight in their lazy eye instead of the eye patch?

A squint operation can only restore the use of the two eyes together and / or improve the appearance of the squinting eye. It does not treat the poor vision in the amblyopic eye, this can only be done by patching / atropine drops and / or glasses.

Is it worth me patching at all? A two-hour dose of patching has been recommended, but my child will only wear the patch for half an hour.

Yes, any patching is better than none at all and you may be able to gradually increase the length of time the patch is worn as your child’s vision improves.

Do I have to do the patching in one session each day? What do I do if I forget one day?

The patching can be worn continuously for the prescribed time or it can be split up eg. 2 hours continuously or two 1 hour slots – whichever fits best into your routine.

However, many parents find that splitting it up causes more "fuss" from the child! If you forget to patch one day try to patch for twice the recommended time the next day.

I have noticed the squint sometimes swaps over into the good eye. What should I do?

If the squint swaps into the good eye occasionally this is a good sign for the vision, it means that the vision is becoming more equal in the two eyes.

If the squint just swaps over occasionally keep patching for the recommended time.

If at any point you think that the good eye is turning more than the “bad” one then you should stop the patch and contact your eye clinic for advice.

How many hours a day will the patch have to be worn for?

There is good evidence that 2 hours of patching a day is as effective as 6 hours of patching for moderate cases of amblyopia (vision between 20/40 – 20/80 or 6/12-6/24).

In more severe amblyopia patching for 6 hours per day is usually recommended.

It has been shown that full time patching is no more effective than patching for 6 hours per day, even in severe amblyopia.

How long will patching be needed for?

The duration of patching will depend on the severity of the amblyopia, the age of the child and how well the child and their parents are able to stick to the prescribed patching regimen.

Will the improvement in vision be permanent?

In approximately 80% of children the visual improvement is maintained for at least a year after patching is stopped. Recurrence of the amblyopia is more likely to occur if patching is stopped Suddenly, if the amblyopic eye is much more long sighted than the good eye (anisometropic amblyopia) or when the amblyopia is a combination of strabismic and anisometropic amblyopia.

This is why it is important to continue monitoring the vision until the child is 8-9 years of age, so any recurrence of the amblyopia can be treated.

When is it too late to start patching treatment?

Although the connections between a child’s eyes and their brain are normally fully formed by the age of 8-9 years, occlusion therapy can still be successful up to the age of 14 in some cases.

What happens if the vision does not improve with glasses, patching and /or atropine penalisation?

Occasionally the vision in the amblyopic eye does not improve despite the fact that the glasses have been worn full time and patching and / or penalisation has been carried out as instructed.

When this happens the ophthalmologist will re-examine the back of the eye again to make sure that there is not a subtle abnormality of the optic nerve or retina (which might not have been apparent at the time of the initial examination), that could be the cause of the poor vision.

How often should a child should come for check up?

It depends on the severity of the condition. usually close follow up may require from 3-6 months


Mahathma Eye Hospital Private Limited
No. 6, Seshapuram,
Tennur, Tiruchirappalli-620 017.
Phone : 91-431-2740494 , 2740494, 2741198

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