Squint

When we look straight ahead at a far object our eyes are parallel to each-other, and when we look at a near object then the line or axis of eye point towards the object of regard. In squint this relationship of two eyes is disturbed. Also known as “strabismus”, squint is a condition where the eyes are not aligned in the same direction. The squinting eye may turn in (converge), turn out (diverge) or sometimes turn up or down. These can be present all or only part of the time, in one or alternating between two eyes.

What causes squint?

It can arise because of an incorrect balance of the muscles that move the eyes ,faulty nerve signals to muscles, refractive errors, childhood illnesses, etc.

Is squint only a cosmetic problem?

Squint is not just a cosmetic problem. It is always associated with certain degree of functional defect which make it important to treat squint as early as possible. It can be associated with decreased vision (amblyopia or lazy eye) or double vision (diplopia). Loss of binocular vision (ability to use two eyes together) can lead to loss of fine depth perception (stereopsis) and peripheral visual field.

What is Amblyopia?

Amblyopia or lazy eye means decrease in vision occurring in the eye due to abnormal or lack of coordination between two eyes. This decrease is over and obove what is caused by refractive error or any other physical problem in the eye. It can be treated before the age of about 9 years by occlusion therapy.

How is squint assessed?

It is assessed by various orthoptics tests, the aim of which is to:

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Establish the amount and type of squint
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Assess how well can the child /adult see
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Detect presence of refractive errors (refraction)
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Test for binocular vision
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Retina examination including fixation pattern
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Investigate for the cause of squint

Childhood Squint

Squint can present at any age. The cause is not always known, but if squint is suspected, then the baby should be seen for accurate assessment at the earliest opportunity. Sometimes a “pseudo or false squint” may be present due to wide gap between the eyes , flat nose bridge etc. where the eyes appear to be misaligned but do not actually have squint. Newborn child may have a certain degree of misalignment of the eyes which usually disappears by about 6 months of age but if it persists beyond 6 months then the child should be immediately examined by an eye surgeon.

What are the causes of childhood squint?

The cause of squint in children is varied:

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Congenital squint: these children are born with a squint, though it may not be obvious for few weeks. A strong family history could be present. In all children the vision and need for spectacles has to be assessed.
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Long sightedness or hypermetropia: as the child cannot focus well for near, he has to put extra effort to focus. The over focusing produces double vision. To avoid this double vision, the image in one eye is suppressed unconsciously and in turn the child avoids using that eye. If left untreated not only does the eye deviates but also becomes a lazy eye (amblyopia)
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Childhood illnesses: Squint may also develop following viral fever, measles, meningitis etc
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Injury: to the nerves supplying eye muscles can lead to squint.
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Hereditary

What is the treatment for childhood squint? Spectacles or Surgery?

The child is thoroughly assessed to establish the type of squint. It is very important to note the vision and fixation pattern in both eyes. Treatment varies according to the type of squint and can be in the form of spectacles, occlusion, eye-drops (rarely) or surgery.

Some squints, especially those that arise from hypermetropia (long sightedness) respond well to treatment with wearing of spectacles. The child will be seen from time to time to note the change in spectacle power and degree of squint till he grows up. Any residual squint not corrected by spectacle can than be corrected by surgery.


Convergent Squint in a 5 years old girl


Almost completely corrected by glasses (Bifocal - parents were shocked at the idea of bifocal but correction of squint relieved them)

Amblyopia / Lazy eye: This is treated by patching / Occluding the good eye. The weaker eye is encouraged to work harder with visual activities such as coloring and reading while patch is on. It should be noted that amblyopia can be treated only before the age of about 9 years after which the visual system of the eye becomes fixed and fails to respond to occlusion therapy.

Surgery: Sometimes this is the only choice to straighten the eye. If done at appropriate time results can be very good and 3 D vision can develop. One or both the eyes may have to be operated and one or more operations sometimes may be required to achieve perfect functional results (cosmetic correction is usually easier to obtain).

Adult Squint

When an adult presents with squint it is not only imperative to establish the type and amount of squint but also to establish and treat the cause of squint. There are two main types: non-paralytic or paralytic squint. The non-paralytic variety either persisted from childhood or is a local eye muscle imbalance. Any adult presenting with sudden onset of paralytic squint has to be investigated in detail for the cause, which could be medical, e.g. hypertension, diabetes mellitus or surgical e.g. brain lesion. Majority of these kinds corrects on their own within 6 months and surgery is only required in cases where squint persists.

What happens in squint surgery?

There are six muscles attached to the outside of each eyeball, which move the eye in various directions. During surgery one or more (commonly two) muscles are weakened or strengthened (by moving their attachment backward or forward) to make the eye straight. The procedure is done under local anesthesia in adults and general anesthesia in children.

Will more than one surgery be required?

It is not uncommon for more than one operation to be necessary. This does not mean that something has gone wrong but that fine-tuning is needed to obtain the best straight alignment. Sometimes the squint is too large and hence a two-stage surgery is planned. The world over average is 2.3 operations to achieve ideal correction of squint.

What happens after the operation?

It is a day care surgery with no hospitalization (unless general anesthesia is used). The eye pad is removed the next day and eye drops are instilled for a couple of weeks. Since it is an external surgery there is no effect on the vision. Most of the times external stitches are absorbable and do not have to be removed. The person can join back his office in a couple of days although a certain amount of redness and irritation continues for a few days.