There may be some assessments that you have experienced at an eye exam and asked yourself how they work. Having a bright light shined into your eyes may be an example. This test is called a retinoscopy examination, which is a preliminary 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 one test your eye doctor can employ to see whether you need eyeglasses.
Basically, what we are doing during a retinoscopy exam is checking how accurately your eye focuses. We begin the exam by looking for what's known as your red reflex. The retinoscope sends light into your eye, and a red or orange light reflects through your pupil and off your retina. The angle at which the light reflects off your retina, also called your focal length, is precisely what tells us how well your eye can focus. If it becomes clear that you can't focus well, we hold a few prescription lenses in front of your eye to determine which one will correct the refractive error.
These exams are performed in a darkened room. The patient will usually be told to focus on something behind the doctor. 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 good way to accurately determine the prescriptions of the speech-impaired, or young children.