If you're having trouble reading street signs, or even this computer monitor, you probably need an eye examination. But who to call? An ophthalmologist, optometrist or optician? All are eye care professionals. But how do they differ?

Ophthalmologist

An ophthalmologist is a physician -- either a medical doctor (M.D.) or a doctor of osteopathy (D.O.) -- who specializes in eyes. Ophthalmologists are qualified to diagnose, manage and treat all optical, medical and surgical disorders of the eye and visual system. They may perform surgery and prescribe medications. Ophthalmologists may also prescribe contact lenses and glasses and recommend the use of eye exercises (orthoptics) to preserve or restore vision. Their training includes four years of medical school, one year of a medical internship and three or more years of a residency in ophthalmology. They must be licensed by their state and may take additional examinations to become certified by the American Board of Ophthalmology.

Optometrist

Optometrists or Doctors of Optometry (O.D.) are primary health care providers who examine, diagnose, treat and manage diseases and disorders of the visual system, the eye and associated structures as well as diagnose related systemic conditions. They examine the internal and external structure of the eyes to diagnose eye diseases, systemic diseases and vision conditions. Optometrists also do testing to determine an individual's ability to focus and coordinate the eyes, and to judge depth and see colors accurately. They prescribe eyeglasses and contact lenses, low vision aids, vision therapy and, in most states medicines to treat eye diseases. After undergraduate college, optometrists complete an additional four years at an accredited school or college of optometry. Optometrists must also pass an examination and have a state license to practice.

Optician

Opticians are allied health professionals, trained to manufacture, fit and dispense eyeglasses and contact lenses and low vision aids upon the doctor's written prescription. Opticians provide specialized services and a wide range of products, utilizing technological advances in frames and lenses to precisely fit each eyewear consumer.