Processamento visual de contraste em pacientes com depressão maior

Abstract

The present study aimed to investigate potential changes in visual perception related to major depression. Then, we measure of contrast sensitivity (CS), one of the most used tools to study the humans visual system. The CS has established itself as one tool that allows to study and identify how certain diseases affect the vision and the central nervous system. The study included 33 volunteers aged between 19 and 37 years and they are normal or corrected visual acuity. 11 were diagnosed with major depressive disorder according to DSM-IV and were treated with antidepressants (Depression Group-DG). The other 22 were free of neuropsychiatric disease and were in good health (Control Group-CG). The CS was measured using the psychophysical method of forced choice between two temporal alternatives (2AF). Were tested linear spatial frequencies of 0.5, 2.5, 10 and 20 cycles per degree of visual angle (cpd) and the angular frequencies of 2, 4, 24, 48 and 96 cycles/360º. The stimuli were circular and were presented on a video monitor LG 19-inch RGB (screen resolution of 1024 x 768 pixels at 75 Hz) connected to a microcomputer and a BITS + + (Cambridge Research Systems). The average luminance of the display was 41.05 cd / m² measured by a photometer ColorCal (Cambridge Research Systems). The measurements were performed at a distance of 300 cm from the monitor screen. The stimuli were displayed in successive pairs, with a frequency tested (linear or angular) and the other was a gray circle with uniform luminance. Participants were instructed to press the left mouse's button when the test stimulus was presented first, and the right button when the stimulus was presented second. The results showed an interaction effect for the linear spatial frequency [F (3, 93) = 6.0814, p = 0.0008], the test post-hoc Newmann Kels showed significant difference in frequency of 0.5 cpd. The results for the angular frequencies showed a marginally significant effect of interaction. The analyzes with post-hoc showed a marginally significant difference for frequency of 2 cycles/360º. These results suggest changes in the CS of patients with major depression medicated.