1. The professional practice of primary eye and vision care that includes the measurement of visual refractive power and the correction of visual defects with lenses or glasses.
2. The practice of non-medical eye care, dealing primarily with the testing of vision for refractive errors and with the prescription and fitting of corrective lenses.
3. The professional practice of eye and vision care for the diagnosis, treatment, and prevention of diseases and conditions of the eyes and visual systems.
4. The practice of examining eyes in order to determine levels of vision and then prescribing and supplying any necessary corrective lenses.