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Retinoscopy: How Does it Work?

There may be a few tests that you have experienced at an eye exam and wondered what they measure. Having a bright light shined into your eye may be one of them. Such as test is used to help test the refractive error of your eye, and it's called retinoscopy. Whether you're near or farsighted, or you have astigmatism, examining the reflection of light off your retina is a way your optometrist can see whether you need vision correction.

Essentially, what we are looking for during the retinoscopy exam is checking how well your eye focuses. We do this looking for what's known as the red reflex. The retinoscope sends light into your eye, and a reddish light reflects through your pupil and off your retina. This process measures your focal length, or in layman's terms, it will measure the angle at which light refracts off your retina. And this is what lets us know how well your eye focuses. And if it's apparent that you can't focus well, that's when we use a set of lenses. We hold up different prescription lenses in front of the eye to determine which one fixes the error. And that is exactly how we find out what prescription your glasses or contact lenses need to be.

All this happens in a dark or dimmed room. To make your eyes easier to examine, you'll generally be instructed to keep your eyes fixed on something behind the doctor. The exam doesn't include charts to be read, which means that a retinoscopy exam is also a really useful tool to determine the prescriptions of the speech-impaired, or young children.

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