CONICET | Buscador de Institutos y Recursos Humanos

The aim of this experiment was to investigate the effect of the age as one of the human factor on off-axis contrast sensitivity function. We considered night-time driving conditions characterized by a mesopic adaptation from the range dominated by rods until values corresponding to the range cone dominated. We conducted a controlled laboratory experiment measuring contrast sensitivity functions with sinusoidal gratings of 1, 2, 3 and 5 c/deg of spatial frequency and mean luminances of 0.1; 0.3; 1 and 3 cd/m2, presented at 10° off-axis. The size of the stimulus was of 2° and the size of the adaptation field was of 32.5 cm by 24.5 cm at 2 m of observation distance. The color temperature of the mean luminance was about 9000 K (The CIE standard illuminant closest is D75 with 7504 CCT (K)). Two observers participated in this study. They were 29 and 62 years old, were ocularly healthy with foveally best corrected visual acuity and normal color vision. A chin rest and a small red light were employed to fixate head movements and gaze respectively. After adaptation to each level of luminance subjects had to discriminate between two possible orientations of the grating using a constant stimuli method. Results show: a) all CSF curves for the older observer are lower than those obtained for the younger one; b) the CSF for 0.3 cd/m2 for both observers present higher values than those corresponding to 1 cd/m2 except for the highest spatial frequency. The results show that age is an important human factor that should be considered in studies of mesopic adaptation in driving tasks. The observed behaviour in relation to the luminance levels could be explained by considering the effects of the rod and cone spectral and spatial sensitivity.