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

JUAN ANTONIO APARICIO; ISABEL ARRANZ; BEATRIZ MATEZANZ; JUAN VIZMANOS; L PADIERNA; V. GONZÁLES; JUAN MENÉNDEZ; SANTIAGO MAR; LUIS ISSOLIO

Ophthalmic and Physiological Optics

Blackwell Publishing

Año: 2010 vol. 30 p. 188 - 199

0275-5408

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 weremeasured 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 testchart background luminance of 200 cd m)2.Results: The letter contrast sensitivity increased with surround luminance up to 100 cd m)2 anddecreased when surround luminance increased from 100 to 1000 cd m)2. These increments arelarger for higher fundamental spatial frequencies, while decrements are similar for all frequencies. Toanalyse pupil size influence, results were compared with theoretical predictions obtained bycombining different ocular MTFs with a typical neural function, where pupil size decrease leads toletter contrast sensitivity increments and veiling luminance causes the observed decrements. Otherpossible optical or neural factors that influence these values have also been considered.Conclusions: Letter contrast sensitivity function depends on surround luminance and this influenceshould be considered in future standardized directives.