There may be a few tests that you have experienced at an eye exam and questioned how they work. Having beams of light shined into your eyes may be an example. Firstly, this test is known as a retinoscopy examination, and if you struggle with accurate vision, this is one way the eye doctor could assess it. By examining the reflection of light off your retina, your eye care professional can decide whether you are nearsighted, farsighted or have astigmatism. This is how they may also measure the prescription you would need to correct your vision.
The most important thing an eye doctor is looking for during this exam is how well your eyes can focus on the light. When light shines into your eye using a retinoscope, a reddish orange light reflects off your retina, through your pupil. We call this the red reflex. 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 lets us know how well your eye is able to focus. If it becomes clear that you are not focusing well, we hold up a variety of prescription lenses in front of the eye to determine which one rectifies the error.
Your optometrist will perform your exam in a dark or dimmed room. You will usually be instructed to focus on something behind the doctor. Because a retinoscopy exam doesn't require you to read eye charts, it means that it's also a really great way to determine the prescriptions of kids who might struggle with speech, or others who might be speech-impaired.