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Antonio Longo, Martial Geiser, Charles E. Riva; Subfoveal Choroidal Blood Flow in Response to Light–Dark Exposure. Invest. Ophthalmol. Vis. Sci. 2000;41(9):2678-2683.
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purpose. To document the response of subfoveal choroidal blood flow (ChBF) in
the human eye induced by light and dark exposures and provide some
insight into the mechanism underlying this response.
methods. In a group of 12 volunteers (age, 25–60 years), ChBF was measured with
a confocal laser Doppler flowmeter. Wavelength of the probing laser
beam was 785 nm (90 μW at the cornea). ChBF was recorded in room
light, in darkness, in room light after dark adaptation, and during
strong green light exposure after exposure to room light. After dark
adaptation of both eyes, ChBF was also measured in one eye while only
the fellow eye was exposed to strong visible light.
results. Although ChBF was stable during room light condition, it decreased
significantly by 15% (P < 0.01) during dark
adaptation. After 6 minutes of room light following 20 minutes of
darkness, ChBF was back to baseline. Strong, diffuse, green light
exposure over a field of 40o, as well as the
probing laser beam, had no detectable effect on ChBF. No change in ChBF
was detected when the fellow eye was illuminated after both eyes had
been dark adapted.
conclusions. The findings did not confirm the presence of an active process of ChBF
regulation in response to light exposure in humans. They demonstrate,
however, a reversible decrease in ChBF that occurs after a transition
from room light to darkness, which could involve a neural
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