On occasion, particularly when doing an eye exam on a small child the eye doctor will direct a beam of light in the eyes. But what does this do? Firstly, this test is known as a retinoscopy examination, and if you struggle with accurate vision, this is a basic way the optometrist might assess it. Whether you're near or farsighted, or you have astigmatism, examining the way light reflects off your retina is a test your optometrist can use to see whether you need vision correction.
Basically, what we are looking for during a retinoscopy exam is checking to see how your eye focuses. We do this looking for what's known as your red reflex. The retinoscope sends a beam of light into your eye, and a red or orange light reflects through your pupil and off your retina. This process measures your focal length, or in simpler words, to calculate the precise angle at which light refracts off your retina which tells us how well your eye focuses. If it becomes clear that you aren't focusing correctly, that's when we use a set of lenses. We hold a number of lenses with varying prescriptions in front of your eye to see which one corrects the error.
The retinoscopy exam is usually conducted in a dark room. To make your eyes easier to examine, you'll usually be instructed to focus on something behind the doctor. Not having to read any eye charts means that a retinoscopy exam is also a really useful tool to determine the prescriptions of the speech-impaired, or young children.