Strabismus, an eye misalignment caused by the imbalance in eye muscles. Because of the imbalance, the muscles lose their ability to move both the eyes in an aligned fashion to focus an object, often leading to one of the types of strabismus. Binocularity and depth perception (3D view) is determined by how your eyes are aligned. Higher the misalignment, lower the binocularity and depth perception.

You must not confuse a "lazy eye" (an amblyopic eye) with one of the types of strabismus. Strabismus may be one of the causes of the "lazy eye", but they are different to each other.

Strabismus can be classified in to two categories, viz.

• Comitant Strabismus, the type of strabismus where the degree of misalignment remains the same irrespective of which direction you look.

• Incomitant Strabismus, the type of strabismus where the degree of misalignment keeps changing with respect to the direction you look.

While an eye remains normal, the other eye might develop on of the following types of strabismus that can occur in either of the categories explained above.

• Esotropia also known as "crossed eyes" where the second eye turns inward
• Exotropia also known as "wall eyes" where the second eye turns outward
• Hypertropia where the second eye turns upward
• Hypotropia where the second eye turns downward

The above said strabismus categories with the types explained could be intermittent or alternating. As the name says, intermittent strabismus appears sometimes, but not all the time. Alternating is a very rare condition where the strabismus alternates between the eyes. Sometimes the first eye may seem to have strabismus, but at other times, it might be the second eye.

There is no known cause for strabismus. But known reasons like short-sightedness, long-sightedness and astigmatism on one eye causes strabismus. So the treatment could be easier when the problem is identified as early as any age lesser than 6 years. Children under 2 years could also be tested, so no children is too early for this test or treatment. After 6 years, it doesn't matter when the treatment is given because by that time the visual system would have been fully-grown. Any strabismus detected after this age is termed as "adult-onset strabismus".

The treatment varies depending on the condition, but in general, the strabismus could be treated by:

• Eye co-ordination exercises using patching the normal eye to allow the brain to tune the misaligned eye to straighten itself. This is a slow process, but works if the misalignment is minor and detected at the early childhood.
• Glasses could reduce the amount of misalignment, but might be necessary to be worn all through the life unless a suitable surgical method is adopted to correct the misalignment.
• Prisms incorporated with the glasses could be used to avoid the double vision.
• Surgery could be performed even on children as young as few months old, if the binocular vision could be achieved. Surgery involved detaching and attaching the eye muscles from one place to another to improve the alignment.