Quantitative and functional influence of surround luminance on the letter contrast sensitivity function.

Aim: To determine the influence of surround luminance on the letter contrast sensitivity function.

Method: The binocular contrast sensitivities of 31 young and ocularly healthy individuals were measured with letters of sizes calculated to obtain the targeted fundamental frequencies of 3, 10, 20, and 30 c deg(-1), respectively; with surround luminances from 1 to 1000 cd m(-2), always with a test chart background luminance of 200 cd m(-2).

Results: The letter contrast sensitivity increased with surround luminance up to 100 cd m(-2) and decreased when surround luminance increased from 100 to 1000 cd m(-2).