This is what the doctor uses to get your eyeglasses prescription. You look at a chart, usually 20 feet away, or in a mirror that makes things look like they’re 20 feet away. You’ll look through a tool called a phoropter. It lets the doctor move lenses of different strengths in front of your eyes.
You can tell them if things look clear or blurry. Your answers give them your prescription for your glasses or contact lenses. The test will also help them spot presbyopia, hyperopia, myopia, and astigmatism.