Influence of age on contrast threshold detection for urban lamps with different spectral distribution in the mesopic range

ISABEL ARRANZ; BEATRIZ MATEZANZ; LUIS ISSOLIO; BÁRBARA SILVA; ELISA COLOMBO; JOSÉ ANTONIO MENÉNDEZ; SANTIAGO MAR; JUAN ANTONIO APARICIO

Sendai

Simposio; The 23rd Symposium of the International Colour Vision Society; 2015

International Colour Vision Society

The streetlamps employed at nigh lighting conditions produce luminance levels within the mesopic range. Usually, the visual performance in these conditions is analysed by using models for mesopic spectral sensitivity that consider different factors such as the luminance and the chromaticity of the visual scene, the retinal location, the visual task, and the type of illuminant. However, all these models have been developed from measurements performed on young subjects. In this study, we have analysed the effect of age and type of illuminant on the achromatic contrast detection thresholds. Measurements have been performed with a double Maxwellian view optical system. Three age groups (young 24,26 years old, mid-age 41,43 years old, old-age 64,65 years old), two different light sources (metal halide MH, S/P = 1.17, CT = 2800 ºK and high pressure sodium HPS, S/P = 0.48 and CT = 2000 ºK), two retinal locations (fovea and 10º), and four background luminances (0.01, 0.07, 0.45, and 3.4 cd/m2) were considered. Test and background were illuminated with the same spectral composition. In foveal vision contrast detection threshold was not influenced by variables such as the illuminant type or age. In eccentric vision and low background luminance conditions (0.01 cd/m2), contrast sensitivity was higher with HPS than MH in old-age subjects, while this situation is opposite to young subjects. In these conditions, adaptation and detection are governed by rods. In young subjects, the higher spectral sensitivity of rods to shorter wavelengths produces lower contrast detection thresholds for MH lamps than for HPS lamps. Opposite, in the old age group, the increase in the straylight due to the prereceptoral media aging produces an important increment in contrast detection threshold. This increment is particularly observed at very low background luminances where rods are very sensitive, while at higher background luminance the effect is not so significant since detection is mostly due to cones. The directional sensitivity of these photoreceptors (Stiles-Crawford effect) makes them less sensitive to intraocular scattering. We can conclude that the influence of age on contrast detection thresholds seems to be different for the two compared illuminants within the mesopic range. Therefore, the age should be included as a parameter in mesopic vision models.