Visual acuity testing refers to how well you are able to correctly identify letters on a chart, cards, or screen. The most commonly used is a Snellen chart. For younger patients that don’t read yet, we sometimes use charts or cards with shapes to test for visual acuity.
The charts and cards are standardized in order to accurately measure individual performance. You will be asked to take off your glasses or take out your contact lenses (if you wear either) before we administer the test. If you are doing an annual exam, sometimes the doctor will want you to try reading the chart with your glasses or contacts, as well, in order to see how well you can perform with your current prescription.
Typically, the chart or cards are displayed at a distance of 20 feet. There are specialized charts made for spaces where the test must be given at shorter distances.
The most common chart will have rows of letters. The top row will have big print. The following rows will have smaller and smaller print. You will be asked to read the letters in each row as far down as you can go until you can no longer identify the small print. If you can read the smallest print at the bottom of the chart without issue, it’s a good indication that you have decent visual acuity.