There may be some assessments that you have seen during an eye exam and questioned what they are for. Having a bright light shined into your eyes could be an example. Such as test is used to help test the refractive error of your eye, and it's known as a retinoscopy exam. Whether you're near or farsighted, or you have astigmatism, examining the reflection of light off your retina is one test your optometrist can use to see whether you need vision correction.
Essentially, what we are doing during a 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 known as the red reflex. This process measures your focal length, or in other words, to calculate the angle of refraction of light off your retina. And this is what tells us how well your eye focuses. If it's apparent that you can't focus correctly, that's where the lenses come in. We hold up a number of lenses with varying prescriptions in front of the eye to see which one corrects your vision. That lens power is the prescription you require to fix your impairment with glasses or contact lenses.
Your retinoscopy exam is conducted in a dark room. The patient will usually be instructed to look at something behind the doctor. Because a patient isn't required to read eye charts during a retinoscopy exam, it's also a particularly useful way to determine the prescriptions of kids who might struggle with speech, or others who might be speech-impaired.