The effect of white light and UV-A on the green autofluorescence of the rabbit lens in vivo.

The part of the light spectrum which is responsible for an increase of lenticular green autofluorescence upon white light exposure was determined for the rabbit. The increase of autofluorescence as a function of the light energy was measured, to assess a possible threshold energy for lens alterations. Thirteen rabbits (Chinchilla Greys) were used. An area of 3 or 4.7 mm2 of the lens was exposed to light from a standard tungsten halogen lamp (250 W, lambda = 360-720 nm). Wavelength selection was performed with the use of light filters. The light dose was adjusted by varying the exposure time between 15 min and 180 min. The green lenticular autofluorescence (lambda exc = 420-490 nm, lambda fluor = 530-600 nm) was measured with a fluorophotometer. A significant increase of lenticular autofluorescence after exposure was observed only if the exposure light contained high wavelength UV-A (lambda = 360-400 nm; 0.8% of the total white light energy); additional white light (without UV-A; up to 13 kJ cm-2) did not have any effect on autofluorescence. The autofluorescence returned to pre-exposure values within 4 days. No lesions could be seen on slitlamp examination. The autofluorescence after exposure to UV-A increased linearly with the exposure energy from 13 J cm-2 (14 mW cm-2 for 15 min) up to 155 J cm-2. The increase was 2.0% of the pre-exposure value per J cm-2 and the correlation coefficient 0.94, P < 0.001. A threshold energy was not found.(ABSTRACT TRUNCATED AT 250 WORDS)