Effect of different phototherapy lights on retinal and choroidal blood flow

The response of retinal (RBF) and choroidal (ChBF) blood flow to illumination with light with different spectra was investigated in spontaneously breathing newborn piglets. After 1 h in complete darkness, the animals were exposed to blue, white or green light in such a manner that equal energy was delivered to the eye. RBF and ChBF showed different flow responses. After 60 min exposure to blue light, RBF increased from 0.22 +/- 0.01 ml/min/g at baseline to 0.32 +/- 0.03 ml/min/g (+/- SEM) (p less than 0.03). Apart from this increase, RBF did not change significantly during any of the experimental settings. ChBF, on the other hand, was significantly affected by illumination. Thus, at 120 min of light exposure all three types of light decreased ChBF significantly from baseline (darkness) levels. Blue light decreased ChBF (mean +/- SEM) from 13.78 +/- 0.84 to 7.61 +/- 0.67 ml/min/g (p less than 0.01), white light from 17.43 +/- 1.86 to 9.86 +/- 1.07 ml/min/g (p less than 0.01), and green light from 14.13 +/- 1.64 to 8.31 +/- 1.30 ml/min/g (p less than 0.02). The results indicate that light is an important modulator of ChBF and to a certain extent also RBF. Further, the results suggest that ChBF and RBF are regulated differently.