Dados do Trabalho

Título

Circadian measurements of visual contrast sensitivity of young adults

Introdução

Circadian rhythms have characteristics that are important to analyze; one initial proposal is their relationship with the mechanisms of visual functions.

Objetivo

Thus, this study used the staircase psychophysical method to investigate luminance contrast variation associated with the course of the daytime circadian clock.

Métodos

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.

Resultados

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]. Participants had a good sleep quality index (M = 5.09 ± 2.6). The Wilcoxon test of related measures showed significant differences at bedtime (Z = 2.37; p = .018), indicating that the participants went to sleep later on the non-working days of the week (01: 35 min ± 72 min) when compared to the weekdays (00: 55 min ± 71 min). 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 Spearman’s rho correlation test showed a correlation in the following variables: spatial frequency of 6.1 cpd at 5:00 pm with the waking time on weekdays (σ = 0.44; p = .039); spatial frequency of 8.8 cpd also at 5:00 pm with the variables of bedtime on weekdays (σ = 0.46; p = .029) and waking time on weekdays (σ = 0.42; p = .049) and non-working days (σ = 0.44; p = .032).

Conclusões

This article discusses the perceptual processes of circadian visual sensitivity. this study discusses nonlinear characteristics of circadian associated with the role of the visual timing system.

Palavras-chave

Circadian rhythms; contrast sensitivity; psychophysica