An ophthalmologist is a physician who specializes in the prevention, diagnosis, and treatment of eye diseases. Diagnostic tests are often ordered only when the results will have a direct impact on the patient's care. The branch of medicine known as experimental ophthalmology works with the diagnosis and treatment of eye problems. It is the study of eye problems, vision, medical, surgical, and optical treatment in the laboratory. Diagnostic tests are essential for determining both infectious and noninfectious causes.