The eyeball is too long and the eye focusses on things in front of an object. If left untreated, the blood supply is cut off to the optic nerve, and blindness can occur. It can happen rapidly or very gradually. It causes the field of vision to narrow and affects night vision.
Children have wide fluctuations in the visual abilities.
This impairment is widely increasing. Most can be corrected with surgery or eye exercises. A major sign is brain malfunctioning or an inner ear problem.