Fluorophotometry was performed in 14 rabbits after exposure of one eye to white light with an energy insufficient to cause visible phototoxic retinal damage as determined by ophthalmoscopy and fundus photography. Fluorescence measurements in the vitreous were performed before and 1 hr after i.v. injection of fluorescein. Ratios between the fluorescein concentrations in the exposed and in the non-exposed fellow eye were calculated after correction for the autofluorescence. The average ratio directly after light exposure had significantly increased (P = 0.005) as compared to pre-exposure values and was maximal one day after exposure (P less than 0.005). Four days after exposure the ratios had returned to pre-exposure values (P greater than 0.05). A significant linear correlation between age and the ratios directly after exposure was found (r = -0.67; P less than 0.01). Signs of phototoxic retinal damage were not found on ophthalmoscopy and fundus photography, nor on light and electron microscopic examination of the retinal pigment epithelium, neuro-retina or retinal capillaries 1 and 4 days after light exposure. A fluorophotometric assessment of the blood-retinal barrier (BRB) function after white light exposure appeared to be a more sensitive parameter of light-induced damage than morphological examination since light exposures at retinal irradiance levels below the threshold for ultrastructural damage resulted in a temporary BRB dysfunction that could be detected by fluorophotometry but not by the other methods.