Psychophysical measure of visual luminance contrast during a daily rhythm

ABSTRACT

This study evaluated visual sensitivity to luminance contrast during a daily period. Twenty-eight young male adults (M = 24.85; SD = 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₍₂₎ = 20.27; p = .001] and in the luminance contrast for frequencies of 13.2 cpd [χ2₍₂₎ = 8.27; p = .001] and 15.6 cpd [χ2₍₂₎ = 13.72; p = .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.

KEYWORDS:

• Psychophysics
• contrast sensitivity
• circadian rhythms
• sleep

Acknowledgments

To the attendants who participated in this research. To the CNPq  =  Conselho Nacional de Desenvolvimento Científico e Tecnológico http://www.cnpq.br/.

Additional Information

Competing Interests: The authors declare that they have no competing interests

Author Contributions

Michael Jackson Oliveira de Andrade (Andrade, M. J. O.)

Maria Thalita Cardoso Rezende (Rezende, M. T. C.)

Bruna Gabrielli Damascena de Figueiredo (Figueiredo, B. G. D.)

Cleciane Alves Farias (Farias, C. A.)

Natanael Antonio dos Santos (Santos, N. A.)

Andrade, M. J. O.: study design, data collection and interpretation, statistical analysis, and article drafing; Rezende, M. T. C.: data interpretation, article drafting and critical revision of the article; Figueiredo, B. G. D.: statistical tools, data interpretation and critical revision of the article; Farias, C. A.: critical revision of the article and statistical tools; Santos, N. A.: study guidance, study design, data analysis and interpretation, and critical revision of the article. All of the author approved the fnal version of the manuscript.