Strabismus, commonly known as eye turn or crossed eyes, is a vision condition in which a person cannot align both eyes simultaneously under normal conditions.
Strabismus may originate in the muscles themselves or in the nerves / vision centres in the brain that control binocular vision.
Kids with strabismus may have one or both eyes turning inwards, outwards, upwards or downwards. The eye turn may be constant or parents may only notice it occasionally (e.g., when their child is tired or looking at something very close up).
When the eyes point in two different directions, they see two different things. To prevent double vision, the brain ignores the image sent by the misaligned eye (suppression).
The more the brain ignores the misaligned eye, the more the vision in that eye deteriorates (a condition known as amblyopia or “lazy eye”), while the straight or straighter eye becomes dominant. If no treatment is given, this may cause permanent vision loss in the amblyopic eye.
In many cases, strabismus is not just an eye muscle issue but how the eye is “wired” to the brain. This explains why an eye turn doesn’t completely go away in some patients even after eye muscle surgery.