Contrast sensitivity testing often isn’t included in a routine eye exam. Your eye doctor might perform the test because of a specific visual complaint you have or because he or she suspects you have a condition that is affecting your ability to discern contrast.
The Pelli Robson contrast sensitivity chart tests your ability to detect letters that are gradually less contrasted with the white background as your eyes move down the chart.
Probably the most widely used device to test contrast sensitivity is the Pelli Robson contrast sensitivity chart.
Like a standard Snellen visual acuity chart, the Pelli Robson chart consists of horizontal lines of capital letters. But instead of the letters getting smaller on each successive line, it is the contrast of the letters (relative to the chart background) that decreases with each line.