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Kozo Masuda, Hiroshi Uozato; Blue streetlights effect on visual acuity in glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5338.
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Blue streetlights are believed to be helpful in preventing suicides and street crime.In Japan, many blue streetlights have been installed. In conditions of rain or fog, blue light when compared to white light, has been shown to decrease visibility and increase the possibility of traffic accidents. Blue cone cells are influenced by intraocular pressure in glaucoma and this influence will appear earlier than visual field loss. We evaluated the effect on visual acuity in moderate defect glaucoma (MDG) by blue light.
We used two healthy volunteers groups (HVG) and MDG group. One HVG 16 volunteers mean aged 30.1 years old (range: 20 - 40) and the other 17 volunteers mean aged 47.9 years old (range: 40 - 60). Nine eyes of 7 MDG patient mean aged 45.0 years old. We decided on two requirements one to have a good corrected visual acuity over 20/20, the other for MDG patients not to have other eye diseases. We tested visual acuity in three different conditions; photopic vision, scotopic vision in white light and scotopic vision in blue light. The luminance of scotopic vision was 1.0±0.5 lx. We considered dark adaptation in this test.
The scotopic visual acuity under both white light and blue light was lower than photopic visual acuity in each three groups. In each groups, there was no significant difference in the scotopic visual acuity under white light, but in glaucoma there was a significant decrease in the scotopic visual acuity under blue light (p<0.01). The scotopic visual acuity under blue light decreased significantly in MDG group compared with the scotopic visual acuity under white light (p<0.01).
Low illumination decreases visual acuity, the decrease on scotopic visual acuity in MSG patients is especially enhanced under blue light. This study suggests that the use of blue light for streetlights should consider the safety of MDG patients and the necessity to increase road illumination.
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