The term eye doctor refers generally to an ophthalmologist, but is also used informally (and imprecisely) in referring to an optometrist. An ophthalmologist is a physician who specializes in the diagnosis and treatment of diseases of the eye. Ophthalmologists may prescribe and fit eyeglasses and contact lenses and also treat eye diseases with drugs and surgery. An optometrist is not a physician. Optometrists are professionally licensed to test a person for vision defects, prescribe and fit glasses and contact lenses, and prescribe therapeutic exercises, but they do not perform surgery and in most U.S. states may not prescribe drugs. An optician is licensed to make, sell, and fit glasses and, in most U.S. states, contact lenses prescribed by an ophthalmologist or optometrist. The term oculist which formerly referred to an ophthalmologist, is no longer used.