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

ISABEL ARRANZ; BEATRIZ MARTÍNEZ MATESANZ; LUIS ISSOLIO; BÁRBARA SILVA; ELISA COLOMBO; J. A. MENENDEZ; SANTIAGO MAR SARDAÑA; JUAN ANTONIO APARICIO CALZADA

Sendai

Congreso; 23rd Symposium of the International Colour Vision Society; 2015

International Colour Vision Society

The streetlamps employed at nigh lightingconditions produce luminance levels within the mesopic range. Usually, thevisual performance in these conditions is analysed by using models for mesopic spectralsensitivity that consider different factors such as the luminance and thechromaticity of the visual scene, the retinal location and the type ofilluminant. However, all these models have been developed from measurementsperformed on young subjects.In this study, we have analysed the effect ofage 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, mid-age and old and two different light sources (metalhalide MH, S/P = 1.17), and high pressure sodium HPS, S/P = 0.48), two retinallocations (fovea and 10º), and four background luminances (Lb = 0.01, 0.07,0.45, and 3.4 cd/m2) were considered. Ineccentric vision and Lb = 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 detectionare governed by rods. In young subjects, the higher spectral sensitivity ofrods to shorter wavelengths produces lower contrast detection thresholds for MHlamps than for HPS lamps. Opposite, in the old age group, the increase in thestraylight due to the prereceptoral media aging produces an important incrementin contrast detection threshold. This increment is particularly observed atvery low Lb where rods are very sensitive; while at higher Lb, the effect isnot so significant since detection is mostly due to cones. The directionalsensitivity of these makes them less sensitive to intraocular scattering. Wecan conclude that the influence of age on contrast detection thresholds seemsto be different for the two compared lamps type within the mesopic range.Therefore, the age should be included as a parameter in mesopic vision models.