Sometimes, especially when doing an eye exam on small children the optometrist will direct a light in the eyes. But why? 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 one test your optometrist can employ to determine whether you need vision correction.
How well your eyes are able to focus during the exam is really what we're looking for. We begin the exam by looking for what we call your red reflex. The retinoscope sends light into your eye, and a red or orange light reflects through your pupil and off your retina. This process measures your focal length, or in simpler words, to measure the precise angle at which light refracts off your retina. And this is what lets us know how well your eye focuses. If it becomes obvious that you are not focusing correctly, that's when we use a set of lenses. We hold up several lenses with varying prescriptions in front of the eye to determine which one corrects your vision. And that is precisely how we find out the prescription your glasses or contact lenses need to be.
The retinoscopy exam is generally performed in a dark room. The patient will usually be told to look at something behind the doctor. Because a retinoscopy exam doesn't involve any eye charts, it means that it's also a really great way to determine an accurate prescription for children or patients who have difficulty with speech.