What is a visual acuity test?

A test of visual acuity measures how many clock hours an object viewed at a given distance will subtend on your retina.

Visual acuity: Acuity tests are standardized charts of various sized objects, usually letters or numbers, which delineate the limits of vision. This can be with or without eyeglass correction. This number can then be used to compare your best vision to others or to legal standards such as the level needed to get a driver's license. It also is used by researchers testing ways to improve vision.