An ophthalmologist is a medical doctor who specializes in treating eye and vision problems. They provide comprehensive eye exams, assess vision, and prescribe eyeglasses or contact lenses if needed. They also test how pupils respond to light, check the alignment of eyes, and make sure the muscles that move eyes are working properly. Ophthalmologists diagnose and treat injuries, infections, diseases, and disorders of the eye. They can prescribe medication taken orally or topically, perform surgery, cryotherapy, and chemotherapy. They are the only practitioners medically trained to diagnose and treat all eye and visual problems, including vision services such as glasses and contacts. Ophthalmologists attend medical school and receive several years of specialty training in the medical and surgical care of the eye.