There may be various assessments that you may have noticed at an eye exam and asked yourself how they work. Having beams of light shined into your eyes could be one of them. This is one way eye doctors test the refractive error of your eye, and it's known as retinoscopy. Whether you're near or farsighted, or you have astigmatism, examining the reflection of light off your retina is one test your eye doctor can use to see whether you need eyeglasses.
How well your eyes are able to focus under the circumstance we create during the retinoscopy exam is really what we're looking for. We begin the exam by looking for what's known as your red reflex. The retinoscope sends a beam of light into your eye, and a reddish light reflects through your pupil and off your retina. The degree at which the retinoscope's light reflects off your retina, also called your focal length, is the thing that tells us how well your eye can focus. If it becomes clear that you can't focus well, we hold up different lenses with varying prescriptions in front of your eye to determine which one will correct the refractive error.
The optometrist will run your exam in a darkened room. To make your eyes easier to examine, you'll generally be instructed to focus on something behind the doctor. The exam doesn't include charts to be read, which means that a retinoscopy exam is also a very useful tool to determine the prescriptions of those who may struggle with speech, like young children and the elderly.