Squint is a condition in which the eyes are not properly aligned, ie, one eye is straight and the other eye is turned away from the straight position. A horizontal squint is convergent when the deviated or the abnormal eye is turned inwards and divergent when it is turned outwards. A vertical squint is one when the abnormal eye is turned up or down. Squints can occur at any age. They can be constant, that is, present all day, or can be intermittent and therefore, occur at different times during the day; especially when the child is tired and unwell.
It is only when we have both eyes straight, we can use them together as a pair and see things in three dimension. This is called binocular vision.
Amblyopia (Lazy Eye):
When a child has squint, he uses only his straight or normal eye to see. Vision in this eye develops normally. The squinting or deviated eye is not used. When a child has constant squint, constant disuse of the squinting eye causes decreased vision in that eye. Hence, the squinting eye becomes lazy. This is called Amblyopia. Amblyopia, is therefore, defective vision in an eye that is not uses constantly.