Psychophysical measure of visual luminance contrast during a daily rhythm

• Published in: Chronobiology international 2019-11, Vol.36 (11), p.1496-1503
• Main Authors: Andrade, Michael Jackson Oliveira de, Rezende, Maria Thalita Cardoso, Figueiredo, Bruna Gabrielli Damascena de, Farias, Cleiciane Alves, Santos, Natanael Antonio Dos
• Format: Article
• Language: English
• ISSN: 0742-0528; 1525-6073
• DOI: 10.1080/07420528.2019.1653904

This study evaluated visual sensitivity to luminance contrast during a daily period. Twenty-eight young male adults ( = 24.85;  = 2.4) with normal color vision and 20/20 visual acuity participated in this study. The circadian pattern was assessed using the Karolinska Sleepiness Scale (KSS), the Pittsburgh Sleep Quality Index (PSQI), and a sleep diary. To measure the luminance contrast, we used version 11.0 of the Metropsis software with sine-element frequency stimuli for spatial frequencies of 0.2, 0.6, 1, 3.1, 6.1, 8.8, 13.2, and 15.6 cycles per degree of visual angle (cpd). The stimuli were presented on a 19-inch color cathode ray tube (CRT) video monitor with a resolution of 1024 × 786 pixels, an update rate of 100 Hz, and a photopic luminance of 39.6 cd/m2. There was a significant difference in KSS on the weekdays [χ2  = 20.27; = .001] and in the luminance contrast for frequencies of 13.2 cpd [χ2  = 8.27; = .001] and 15.6 cpd [χ2  = 13.72; = .041]. The results showed greater stability of the measurement during the afternoon and a reduction in the visual sensitivity in the high spatial frequencies during the night.