There may be some assessments that you may have noticed during an eye exam and wondered what they measure. Having beams of light shined into your eyes could be an example. Firstly, this test is a retinoscopy examination, which is a preliminary way to determine the refractive error of your eye. By just examining the way light reflects off your retina, your optometrist can assess whether you are nearsighted, farsighted or have astigmatism. This is how they may also measure the prescription you would need to correct your vision.
Basically, what we are looking for during the retinoscopy exam is checking to see how your eye 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 retinoscope measures your focal length, or in other words, to measure the precise angle of refraction of light off your retina. And this is what lets us know how well your eye focuses. If it’s apparent that you are not focusing correctly, that’s when we use a set of lenses. We hold a few prescription lenses in front of your eye to see which one corrects the error.
All this happens in a darkened room. You will usually be instructed to look at something behind the doctor. This makes eyes easier to examine. 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.