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[Effect of light on choroidal blood flow in the fovea centralis]
Purpose:
To investigate whether light and dark exposures induce a response of choroidal blood flow (ChBF) in the foveal region in humans.
Methods:
In a group of healthy volunteers (age 25-60 years) ChBF was measured using a new confocal laser Doppler flowmeter (probing laser at 785 nm, power at the cornea = 90 microW). ChBF was recorded at room light, in darkness, at room light following dark adaptation, and during strong light exposure following room light.
Results:
While ChBF was stable during room light condition, it decreased significantly by 15% (p < 0.01) during darkness. After 6 min of room light following darkness, ChBF was back to baseline. Strong diffuse, green light exposure over a field of 45 degrees had no detectable effect on ChBF. In all the experiments, no significant change of blood pressure was detected.
Conclusions:
Our findings did not confirm the presence of an active process of ChBF regulation in response to strong light exposure in humans. They demonstrate, however, a reversible decrease in ChBF occurring after a transition from room light to darkness.