Daily variation of visual sensitivity to luminance contrast: Effects of time of measurement and circadian typology

Abstract

This study analyzed the fluctuation of the achromatic visual contrast sensitivity (CS) of adult males (M = 23.42 ± 2.6 years) during a daily period. Twenty-eight volunteers were divided into three groups according to circadian typology (CT): moderate morning (MM; n = 8); intermediate (I; n = 10) and moderate evening (ME; n = 10). The Pittsburgh Sleep Quality Index was used to evaluate sleep quality, and the Horne and Ostberg Morningness-Eveningness Questionnaire was used to measure CT. To measure CS, we used Metropsis software version 11.0 with vertical sinusoidal grids 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 cathode ray tube (CRT) color video monitor with a 19-inch flat screen, a 1024 × 786 pixel resolution, a 100 Hz refresh rate and a photopic luminance of 39.6 cd/m. It was inferred that there is a tendency for visual contrast to vary according to daily rhythmicity and CT, mainly for the median spatial frequencies (1.0 cpd, χ = 9.93, p < 0.05 and 3.1 cpd, χ = 10.33, p < 0.05) and high spatial frequencies (13.2 cpd, χ = 11.54, p < 0.05) of ME participants. ME participants had minimal visual contrast sensitivity during the morning shift and a progressive increase from afternoon to night.

Circadian Sensation and Visual Perception

“…The results did not show variation in CSV of morning subjects, but detected fluctuation in CSV for night subjects with greater sensitivity in the period of 21:00 in spatial frequencies of 1.0, 3.1 and 13.2 cpg, and fluctuation in CSV for intermediate subjects in spatial frequencies of 0.2 and 15.6 cpg. Furthermore, the study by Andrade et al [27,31] pointed out that intermediate subjects have maximum sensitivity in spatial frequency 0.2 cpg at 17:00 when compared to 9:00 and 13:00 times. There was an attenuation in visual sensitivity during the morning in all groups, except for morning subjects.…”

“…Studies by Tosini [22] and Tosini, Pozdeyev, Sakamoto and Luvone [23] suggest that the retina also has a circadian clock capable of controlling visual processing functions. Numerous studies have shown that visual sensitivity, defined by means of visual contrast thresholds, has a circadian behavior in several species, among them: zebras [24], Larval Xenopus [25], rats [26], and humans [27][28][29][30]. These results, in general, culminate the idea that the filtering of properties of human visual processing occurs according to the circadian variation of visual sensitivity.…”

“…Remember that rods and cones ingrate ipRGCs and, consequently, circadian behaviors may be associated with these mechanisms. Recent findings have shown that mechanisms that process the contrast of luminance and color are associated with the circadian timing pattern [27,31].…”

“…Recent studies prepared by Andrade, Silva, and Santos [44] and Andrade et al [27,31] evaluated CSV circadian fluctuation in healthy adult subjects according to circadian typology at different times of the day. These studies indicate that CSV curves have minimum sensitivity at 09:00, progressive increase from 13:00 to 17:00 and maximum sensitivity at 21:00.…”

“…Andrade et al [27,31] also evaluated CSV according to circadian typology and measurement time of adult men (M = 23.42 ± 2.6 years) during a daily period. The authors observed that CSV curves had decreased sensitivity for low and high spatial frequencies [46] and peak sensitivity for average spatial frequencies [42].…”