Optometrists spend most of their time testing the vision systems of their patients. The qualities tested include the ability to focus and coordinate the eye, gauge depth perception, and accurately distinguish between colours. When an Optometrist ascertains that a patient has an issue with an aspect of their vision, he or she will prescribe the appropriate treatment for the ailment, from corrective eyewear, to medication and surgery.

Take the example of a patient presented with glaucoma: Optometrists often may be the first medical professional to recognize this disease in their patients. Glaucoma is a disease of the optical nerve and it is often diagnosed after a battery of vision and pressure tests of the eye, all of which are aimed at identifying the telltale signs of nerve damage. There are a variety of treatments from which an Optometrist will choose based on the specific condition of the patient and nature of the glaucoma, ranging from medication to drainage implants to surgery. Often times for glaucoma, the best option for the patient will simply be medication, but the Optometrist will always be prepared to take more drastic action if the disease and situation warrants, such as the aforementioned surgical and implant options.

In addition to concerning themselves with the vision systems of their patients, there are many clues to overall patient wellbeing as well as general health and nutrition factors that Optometrists may notice over the course of a standard vision test. They often can detect systemic diseases based on evidence they find during these tests, providing a vital primary care service to their patients.