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Kozo Masuda, Hiroshi Uozato; Effect of color illumination from street lights on scotopic visual acuity. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6238.
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Lights of different wavelengths are used for street lights. In rainy or foggy conditions short-wavelength light has been shown to decrease visibility and increase the possibility of traffic accidents. We evaluated the effect of different colors’ wavelength at different luminance on scotopic visual acuity.
We used 15 healthy volunteers mean aged 32.8±9.0 years old (mean ±SD), using their right eye with no other eye diseases except for refractive error. We measured the scotopic visual acuity after the measurement of corrected visual acuity in photopic condition. The luminance in scotopic vision was 0.1 lx, 1.0 lx, and 10.0 lx at the optotype surface. The source of light used wavelengths of about 450nm (blue), 600nm (orange), and white light which consisted of three wavelengths of blue, green and red. We considered dark and color adaptation in this test. We measured angular vision at a distance of 3m in the white, orange and blue order and lighted each color from a lower to higher luminance. We analyzed the data using multiple comparison tests.
The mean visual acuity (LogMAR) of each color (white, orange, blue) was (0.637, 0.621, 0.697) under 0.1 lx, (0.201, 0.196, 0.247) under 1.0 lx, and (-0.002, -0.030, 0.027) under 10.0 lx. There was a significant difference between the orange and blue light under 10.0 lx(p<0.05). There was no significant difference under 0.1 lx and 1.0 lx, but a decrease of visual acuity under blue light (short wavelength) was observed when compared with the results from other colors.
This study shows that scotopic visual acuity is affected by different luminance and colors’ wavelength. We suggest to take into consideration the decrease in visual function when selecting short-wavelength blue lights for street lights.
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