Both are eye doctors that diagnose and treat many of the same eye conditions. The American Optometric Association defines Doctors of Optometry as: primary health care professionals 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 prescribe glasses, contact lenses, low vision rehabilitation, vision therapy and medications as well as perform certain surgical procedures.
The main difference between the two, is that ophthalmologists perform surgery, where an optometrist would not, preferring to specialize in eye examinations, as well as eyeglass and contact lens-related services.
Optometrists would be involved in all of the pre- and post-operative care of these patients; collecting accurate data, educating the patient, and insuring proper healing after the procedure. An ophthalmologist is more of a medical-related specialist, who would need only to be involved if some kind of surgery were being considered. An optometrist can treat most any eye condition, including the use of topical or oral medications if needed. This might include the treatment of glaucoma, eye infections, allergic eye conditions and others, to name just a few.
A third "O" that often is overlooked is the optician. An optician is not a doctor, and they cannot examine your eye under their own license. However, a highly trained optician plays an indispensable role in the most successful eye doctors' offices. An optician most often handles the optical, contact lens, and glasses side of things. Based on their vast knowledge of lenses, lens technology and frames, they manufacture eyeglasses, as well as assist in the selection of eyewear, based on the requirements of each individual patient.