Although an optometrist receives a Doctor of Optometry (OD) degree, he or she is licensed to practice optometry, not medicine. The practice of optometry traditionally involves examining the eye for the prescription and dispensing of corrective lenses and detection and non-surgical management of certain limited eye diseases. There are considerable state-by-state differences in optometric scope of practice, with some states permitting use of more pharmaceutical agents than others. 

In comparison, the scope of an ophthalmologist's practice is much broader. An ophthalmologist is a medical doctor (M.D.) who specializes in all aspects of eye care including diagnosis, management and surgery of ocular diseases and disorders. The difference between the training of an optometrist and that of an ophthalmologist is considerable. An optometrist may have only seven years of training after high school, consisting of three to four years of college and four years in an optometric college. An ophthalmologist receives a minimum of 12 years of education beyond high school, which typically includes four years of college, four years of medical school, one or more years of general medical or surgical training, and three or more years in a hospital-based eye residency program. This is often followed by one or more years of subspecialty fellowship.

Beyond the study of correction of refractive errors, optometrists have limited exposure in training for patients with eye disorders or disease. In contrast, ophthalmologists have a full medical education, followed by extensive clinical and surgical training in ophthalmology, with thousands of hours devoted to care and treatment of a much larger volume of sick patients.