The cornea and lens are responsible for focusing light on the retina. Vision problems are most often the result of an imperfectly shaped eyeball, cornea or lens that prevents light from being properly focused within the eye.
National Eye Institute
Debris litters the road after two bombings in the western city of Ramadi, about 60 miles from Baghdad, on Dec. 30. Violence has escalated recently in Anbar province, once the stronghold of al-Qaida in Iraq.
Azhar Shallal/AFP/Getty Images