What is the difference?

Sight tests refer to the process of having your prescription determined by an autorefractor alone. The autorefractor is a machine that estimates your prescription in a matter of seconds when you focus on an image (typically of a hot air balloon or house) at the end of a long road.

Credit: Bryce Wilner

While some may appreciate the efficiency of such a test, it is at most an approximation of refractive error, as the result may be influenced by factors such as eye muscle coordination, eye fixation and alignment, pupil size, corneal or lens irregularities, patient movement and attention, and instrument myopia—the result of the eye’s tendency to over-focus when looking through such a machine. (CAO, n.d.)

In short, automated sight tests should not be relied on solely in determining an individual’s prescription.

An eye examination on the other hand, is performed by an optometrist. He or she is responsible for your eye and vision health, on top of measuring your prescription. This includes tests to detect any asymptomatic eye and health conditions that may not be perceivable to the patient or visible to the naked eye—a process that is crucial to ensuring early detection and prevention of diseases.

Machines may still be used prior to a series of tests to determine your final prescription. However, optometrists are able to draw from their experience, training, as well as interaction with their patients to exercise judgment in deriving a prescription tailored to their individual needs. For example, an optometrist may decide to tune aspects of an elderly patient’s actual prescription when comfort instead of sharpness is their primary concern.

Eye examinations therefore are equivalent to a comprehensive check-up as opposed to a simple temperature reading that is a sight test. We recommend visiting the optometrist at least once every 2-3 years and annually as you get older to ensure optimal vision health and a peace of mind 🙂