Have you ever been in a three legged race? If your synchrony with your race partner is anything like the above, you can get into a whole lot of trouble! Something similar happens with your eyes when they lose coordination. The condition is called strabismus.
Strabismus, also known as squint, is a condition where both your eyes do not look together in the same direction. So if one of your eyes looks straight ahead, the other turns to point inwards, outwards, upwards or downwards. The turning of the eye may remain constant or it may come and go. Most squints are seen in young children; about one in twenty, to be precise. Sometimes squints can develop in older kids or even in adults. Strabismus is also known by many other names like crossed eyes, wandering eyes, cock eye, wall eyed and deviating eye.
When your eye turns inwards (towards the nose), it is called esotropia.
If your eye turns outwards (away from the nose), it is known as exotropia.
When one of your eyes turn upwards or downwards, its is called hypertropia.
Six muscles around your eye are responsible for co-ordinating the movements of your eye. These are called extra-ocular muscles. In order that both your eyes be lined up and focused on a single target, all the muscles in both the eyes have to work together. In a person with normal vision, both the eyes aim at the same object. This helps the brain to combine the two pictures received from the two eyes into a single 3-D image. It is this 3 dimensional image that gives us a perception of depth.
When one eye goes out of alignment in strabismus, two different pictures are sent to your brain.
In a child with crossed eyes, the brain ‘learns’ to ignore the image from the non-aligned eye. Because of this, the child loses perception of depth.
In adults who develops a squint, their brain has already learnt to receive two images and cannot ignore the image from the misaligned eye. Because of this, the adult develops double vision.
• Strabismus develops when there is a problem that interferes with the controlling and functioning of the extraocular muscles. This problem may have to do with the muscles themselves or the nerves or regions of the brain that control the extra ocular muscles.
• Disorders that affect the brain may cause a squint, for eg. Cerebral Palsy (a disorder in which there is impaired muscle co-ordination), Down’s Syndrome (a genetic condition affecting physical and mental development), Brain tumors, Hydrocephalus (Collection of fluid in the brain), etc.
• A cataract, diabetes, eye injury or tumor in the eye that causes vision problems can also cause wandering eye.
• Damage to the retina in premature babies or an hemangioma (abnormal build up of blood vessels) near the eye during infancy may also be a cause.
• Your genes may also play a role in your developing a squint.
• Sometimes, when a child with uncorrected farsightedness tries to focus, he / she can develop something called accomodative esotropia. This happens because of the exxcessive focussing effort.
The main sign of a squint is an eye that is not straight.
When this misalignment is large and obvious, your brain makes practically no efforts to straighten the eye and it does not cause too many symptoms.
When the misalignment is less or if it is not constant, headaches and eyestrain are experienced.
There may also be fatigue when reading, jittery or unstable vision and an inability to read comfortably.
Sometimes, your child may squint one eye when out in bright sunlight or tilt his head to use both his eyes together.
It can also lead to loss of vision in the misaligned eye, a condition called as amblyopia.
Newborn babies often have intermittent squint, but this reduces by 2 months of age and disappears by four months of age as the baby’s vision development occurs. However, most children never outgrow a true strabismus.
Apart from the standard ophthalmic examination, eye tests like:
Visual Acuity testing
Corneal light reflex
Cover/ Uncover Test
Brain and Nervous System testing
If glasses are required, they are prescribed.
Amblyopia or lazy eye needs to be treated first. This is done by patching the good eye so that the weaker eye gets trained to work harder.
If the crossed eyes do not get corrected, eye muscle surgery is indicated. Different muscles of the eye are made stronger or weaker.
Adults with a mild squint that is not constant may benefit from eye exercises and glasses. If you have a severe grade of squint, you would require surgery.
Botox: Botox or Botulinum Toxin stops muscles from working and can be injected directly into eye muscles for certain types of squints.
Early detection is very important. All children should get their vision checked between the ages of 3 months to 3. Years. If you have a family history of strabismus or amblyopia, you should get your child’s eyesight checked even before the age of 3 months.