Influence of age and spectral power distribution on mesopic visual sensitivity

Abstract

The ability of the human visual system to detect stimuli at low illumination levels provides awareness of potential risks. The influence of age and spectral power distribution on mesopic spectral sensitivity is analyzed. Two typical light sources are used, a high-pressure sodium lamp (HPS), with a higher content of long wavelengths, and a metal halide lamp (MH), with a higher content of short wavelengths. Two experiments were performed, using a two-channel Maxwellian-view optical system to measure contrast threshold under different experimental conditions. In Experiment 1, three age groups (young, middle-aged and old, n = 2 each), two retinal locations (on-axis and off-axis vision), four background luminances (0.01, 0.07, 0.45, and 3.2 cd/ m 2 ), and two photometry systems (photopic and the MES2 systems) were considered. In Experiment 2, contrast threshold measurement was performed with two age groups (young and old, n = 11 each), one retinal location (off-axis vision), one background luminance (0.01 cd/m 2 ), and two photometry systems (photopic and the MES2 systems). In on-axis vision, neither age nor spectral power distribution have an effect on the contrast threshold. In off-axis vision, however, a significant interaction between age and spectral power distribution is obtained, albeit only at 0.01 cd/m 2 with an MH lamp. Only at this lowest background luminance was the greater content of short wavelengths of this lamp responsible for higher rod stimulation in offaxis vision, with the subsequent improvement in detection performance in young subjects. However, the effect of diffused light inside the aged eye counteracted the benefits of increased rod sensitivity for the MH lamp.

Effect of the spectral power distribution on visual performance of subjects implanted with intraocular lenses with or without a blue light-filter under night-driving conditions

“…Technol. 2024; 56: [23][24][25][26][27][28][29][30][31][32][33][34][35][36] coming from the light source reaches the retina. The image of the light source has a diameter of 2.5 mm in the entrance pupil of the observer.…”

“…The absolute irradiance spectral power distribution of both lamps was obtained by placing the lamp 50 cm from the entrance slit of a spectrometer, and the results showed that MH lamp has a higher emission in the short-wavelength region, compared to HPS lamp. 32 From the spectral power distribution, the S/P ratios were calculated. The S/P ratios of HPS and MH lamps were 0.49 and 1.17, respectively.…”

“…Technol. 2024; 56: [23][24][25][26][27][28][29][30][31][32][33][34][35][36] performance of both measured tasks, especially under the MH lamp due to its higher shortwavelength content. Cataract surgery and IOL implantation enable old subjects to visually perform more efficiently, regardless of the type of lamp and IOL implanted.…”

“…In the baseline group, CT is lower for MH than for HPS lamp because its higher shortwavelength content strongly activates the blue light-sensitive photoreceptors, rods and S-cones, a finding already reported in the literature. [14][15][16]32 On the other hand, cataract causes the formation of a veil overlaid on the retina 40 that reduces the contrast of the retinal image, resulting in increased CT. In addition, two factors should be considered.…”

“…Technol. 2024; 56: [23][24][25][26][27][28][29][30][31][32][33][34][35][36] on photoprotection and photoreception. Shortwavelength blocking has proved neither to affect photopic and mesopic visual acuity and contrast sensitivity 25 nor to cause disruption in photopic colour vision.…”