There are various assessments that you have seen during an eye exam and asked yourself how they work. Having a bright light shined into your eyes may be an example. Such as test is used to help 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 way light reflects off your retina is one test your optometrist can employ to see if you need vision correction.
How well your eyes focus under the circumstance we create during the exam is the most important thing we look for. We shine light into your eye because we are looking for what's known as the 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 layman's terms, it will determine the angle of refraction of light off your retina which tells us how well your eye is able to focus. If it's apparent that you are not focusing well, that's where the lenses come in. We hold up several prescription lenses in front of the eye to see which one fixes the error.
All this happens in a dark room. The patient will usually be told to focus on an object behind the doctor. Unlike eye examinations you may have had, your doctor won't ask you to read letters off charts. This means that a retinoscopy exam is also a really useful tool to determine the prescriptions of the speech-impaired, or young children.