During an eye examination, you may have had a doctor instruct you to peer straight in front of you while directing a light into your eye. So what does this do? This test is a retinoscopy examination, and if you struggle with accurate vision, this is one way the eye doctor could assess it. By just examining the reflection of light off your retina, your eye doctor can determine whether you are nearsighted, farsighted or have astigmatism, and can also get a pretty good reading on the prescription you would need to correct your vision.
The main thing an eye doctor is checking for during this exam is how accurately your eyes can focus on the light. We do this looking for what we call 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. We use the light to determine your focal length, or in simpler words, to calculate the precise angle of refraction of light off your retina. And this is what lets us know how well your eye focuses. And if we notice that you aren't focusing well, we hold up a few lenses with varying prescriptions in front of your eye to see which one rectifies your vision.
The eye doctor will run your exam in a dark or dimmed room. To make your eyes easier to examine, you'll usually be instructed to look at an object behind the doctor. The exam doesn't include eye charts, which means that a retinoscopy exam is also a really good way to accurately determine the prescriptions of the speech-impaired, or young children.