OPTOMETRIST TOOLS FOR MEASURING YOUR VISION
The visual measurement, or visual acuity (sharpness) portion of your eye exam* begins by taking a look at the Snellen eye chart. A staple in any optometrist's office, the Snellen eye chart is a simple and basic test to determine your vision's proximity to 20/20—essentially how clearly you can see something from 20 feet away. Depending on your result, your eye doctor may then check for any refractive errors (whether you are nearsighted or farsighted). Using the Snellen eye chart, your eye doctor will have you look through a phoropter and test your vision against a series of lenses of varying optical power.
If your eye doctor suspects you may have astigmatism, a keratometer may also be used to measure the curvature and reflection of the front of the cornea. Together, these optometrist tools help your eye doctor narrow down the prescription needed to help you see the world with the clearest, most vivid vision possible.