There may be a few assessments that you have experienced at an eye exam and wondered what they measure. Having beams of light shined into your eyes may be an example. This test is known as a retinoscopy examination, and it's a basic way to assess the refractive error of your eye. Whether you're near or farsighted, or you have astigmatism, examining the way light reflects off your retina is one way your eye doctor is able to determine if you need eyeglasses.
The most important thing an eye doctor is checking for during this exam is how well your eyes can focus on the light. When we use the retinoscope to shine light into your eye, a reddish light reflects off your retina, through your pupil. Eye doctors call this the red reflex. This process measures your focal length, or in layman's terms, it will determine the precise angle at which light refracts off your retina. And this is what lets us know how well your eye focuses. If it becomes obvious that you can't focus well, that's where the lenses come in. We hold up several prescription lenses in front of your eye to see which one fixes your vision. This is precisely how we find out the prescription your glasses or contact lenses need to be.
All this happens in a dark room. To make your eyes easier to examine, you'll usually be told to look at something behind the doctor. Because a patient isn't required to read eye charts during a retinoscopy exam, it means that it's also a really great way to determine the prescriptions of children or patients who have difficulty with speech.