See full answer. Crossed eyes or esotropia is an eye condition classified under strabismus. It can be hereditary, or due to amblyopia ( decreased vision), or any opacities on the lens as cataracts, corneal scars, or retina pathology that cause decreased vision. Also significant hyperopia or farsightness can cause eye crossing . Babies after 4 months of age should not cross at all. Brain tumors can cause esotropia.