Blood-retinal barrier dysfunction at the pigment epithelium induced by blue light

Exposure to low-intensity white light can induce dysfunction of the blood-retinal barrier (BRB) at the retinal pigment epithelium (RPE). To determine whether the shorter wavelengths white light are responsible for this dysfunction, rabbit retinas were exposed to blue light (400-520 nm) or yellow light (510-740 nm). The permeability of the BRB, a parameter for the integrity of the barrier, was quantified with vitreous fluorophotometry. Morphologically, the barrier at the RPE was visualized on light and electron microscopy using horseradish peroxidase (HRP) as a tracer. Seventeen pigmented rabbits were exposed to blue light and 11 were exposed to yellow light. Vitreous fluorescein leakage increased with the exposure energy according to a power function (correlation coefficient > 0.79). The threshold energy for an increase in BRB permeability was 50 J/cm2 (0.014 W/cm2 for 1 hr) after blue and 1600 J/cm2 after yellow light. HRP tracing demonstrated that after blue light exposure, a significant fluorescein leakage on fluorophotometry corresponded to the presence of HRP in the RPE cells and in the subretinal space. After yellow light exposures of < 3700 J/cm2 and in rabbits with no significant fluorescein leakage, the HRP was limited to the choroidal capillaries and Bruch's membrane. These results demonstrate that the blue component of white light causes dysfunction of the BRB at the RPE 30 times more effectively than the longer wavelength fraction of white light. As a result, a blue light blocking filter should be used in ocular surgery on humans when an operating microscope is being used (light power 0.1-0.9 W/cm2).