While you look at a line on an eye chart, your optometrist will flip back and forth between two lenses and ask you to identify which lens provides the clearest image. You'll place your head against a phoropter, a device that contains multiple corrective lenses. Refraction helps your optometrist refine your prescription. Your optometrist uses a variety of tests to determine your prescription, if needed, and assess the health of your eyes, including: Other Eye Tests Augment Your Eye Chart Measurement
In addition to reading the Snellen eye chart, you may also be asked to read text on the small printed card that you'll hold in your hands. If you can read the bottom line of the eye chart clearly, your vision is 20/10. Although 20/20 is considered normal vision, some people can see even better than 20/20. If your vision is 20/60, you can read words clearly at 20 feet that people with normal vision can read at 60 feet. Each line corresponds to a specific measurement, such as 20/20 or 20/80. The chart is read from the top to the bottom. Patients were once required to stand exactly 20 feet away from the chart, but optometrists use mirrors today to approximate that distance. The chart contains 11 lines of random letters, each line smaller than the preceding line. Reading an Eye Chart Provides an Accurate Representation of Your VisionĮvery eye exam includes a reading of the Snellen eye chart. You'll also need a few other tests, in addition to the results of your eye chart reading, before your optometrist hands you your eyeglass prescription.
Have you ever wondered what those numbers on your eyeglass prescription actually mean? Although reading an eye chart is a fairly simple test, it provides a very accurate way to measure your visual acuity or the sharpness of your vision.
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