Strabismus, usually known as cross eye, is relatively common among eye problems.

Between two and four percent of children have esotropia (inward deviation), and 1 to 1.5 percent have exotropia (outward deviation), according to Mayo Clinic.

Uncorrected strabismus can have far-reaching effects, including loss of vision and adverse effects on psychosocial development.

Esotropia, in general, is most urgent in terms of requiring immediate attention to manage any vision loss or adverse effects on stereoacuity.

Exotropia is generally a more intermittent and slowly progressive disorder, allowing for observation over time.

However, a child with any form of strabismus should be seen as soon as possible by an eye specialist to rule out vision loss or a visually dangerous or unexpected cause of the deviation.

Sometimes, esotropia isn't present from birth. A child's eyes might be fine up to age 3 or 4 years but then suddenly start to cross. If the crossing eye is detected early and eyes straightened with surgery in three to six months, the 3D vision starts to work again. If a child lacks the potential for developing normal 3D vision, the eyes are prone to drifting again.

Poor vision due to strabismus that is not corrected before age nine can result in a permanent loss of vision.

Oftentimes, the parents are not aware of when it started. They might think it's been three months when it's actually been there years. Sometimes old pictures of the child are needed to determine the onset.

Exotropia, depending on the severity, can be simply observed or may require treatment such as glasses, part-time patching or even eye muscle surgery. Children with esotropia are generally treated at the time of their first office examination with glasses and patching for those who have amblyopia. Esotropia that does not respond to glasses will require surgery, usually within several months, to preserve stereopsis.

Most of the children with cross eye can be treated by glasses alone and some need surgery. Seven out of eight children will successfully respond with one surgery. In more complicated cases a second surgery and sometimes more is needed, Mayo Clinic says.