There are a few tests that you may have noticed 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 a retinoscopy examination, and it's a basic way to measure the refractive error of your eye. Whether you're near or farsighted, or you have astigmatism, examining the reflection of light off your retina is a way your eye doctor is able to see if you need vision correction.
The most important thing an eye doctor is checking for during this exam is how accurately your eyes can focus. When we use the retinoscope to shine light into your eye, a reddish orange light reflects off your retina, through your pupil. This is called the red reflex. The angle at which the light reflects off your retina, which is what eye care professionals call your focal length, is exactly what tells us how well your eye can focus. And if we notice that you can't focus well, that's where the lenses come in. We hold a variety of lenses with varying prescriptions in front of your eye to determine which one rectifies your vision.
All this happens in a dark or dimmed room. The patient will usually be asked to look at something behind the doctor. This makes eyes easier to examine. Unlike eye examinations you may have had, you won't be asked to read any charts. This means that a retinoscopy exam is also a really useful tool to determine the prescriptions of those who may struggle with speech, like young children and the elderly.