When someone has a squint, there's a problem with their eyes, which are misaligned and look in different directions. So, while one eye seems to look straight ahead, the other will gaze to the left or right, or up or down.

Squint (strabismus) typically involves a lack of coordination between the extra-ocular muscles that prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely affect depth perception.

Diagnosis

During eye examinations, ophthalmologists and orthoptists typically use a cover test to aid in the diagnosis of strabismus / squint. If the eye being tested is the squinting eye, then it will fixate on the object after the "good" eye is covered, as long as the vision in this eye is good enough. If it is the "good" eye, there will be no change in fixation, as it is already fixated.  The eye can point in towards the nose (esotropia) or outwards (exotropia).

In turning left eye in a child- esotropia

Treatment and management

The primary goal for those with strabismus is comfortable, single, clear, normal binocular vision at all distances and directions of gaze.
Early treatment of strabismus and/or amblyopia (weak or lazy eye) in infancy can reduce the chance of developing amblyopia and depth perception problems.

As vision improves in the lazy eye, surgery may be required to re-align the eyes.