There are some assessments that you have experienced at an eye exam and questioned how they work. Having beams of light shined into your eye may be one of them. Firstly, this test is called a retinoscopy examination, and if you have issues with accurate vision, this is one way the eye doctor could assess it. Whether you're near or farsighted, or you have astigmatism, examining the reflection of light off your retina is one test your optometrist can employ to see if you need eyeglasses.
The most important thing your doctor is looking 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 orange light reflects off your retina, through your pupil. This is known as the red reflex. This process measures your focal length, or in layman's terms, it will measure the precise angle of refraction of light off your retina. And this is what tells us how well your eye focuses. And if we notice that you are not focusing properly, that's when we use a set of lenses. We hold up a number of prescription lenses in front of your eye to determine which one will correct the refractive error. This is precisely how we calculate what 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 asked to focus on something behind the doctor. Because a patient isn't instructed to read eye charts during a retinoscopy exam, it means that it's also a really great way to determine an accurate prescription for children or patients who have difficulty with speech.