Picture of Strabismus (Crossed Eyes)
Strabismus, also known as crossed eyes, is a condition in which the eyes don't look toward an object together. One of the eyes may look in or out or turn up or down. The danger with strabismus is that the brain may come to rely more on one eye than the other and the less-favored eye fails to develop properly, leading to blindness in that eye. The classic treatment for mild-to-moderate strabismus has long been an eyepatch covering the stronger eye, which forces the weaker eye to do enough work to catch up. Severe strabismus may require surgery.
Image Source: Dr. Andrew A. Dahl, M.D., F.A.C.S.
Text: MedicineNet - Strabismus