Decrease and Recovery of in vitro Retinal Pigment Epithelium Autofluorescence Intensity in Response to Visible Light

Using in vivo adaptive optics (AO) scanning laser ophthalmoscopy (SLO) equipped with fluorescence imaging capabilities, we previously reported, in the macaque retina, an immediate decrease in RPE autofluorescence intensity in response to visible light, followed by either full recovery or permanent retinal damage. The mechanism of this initial autofluorescence intensity decrease is currently unknown, although the photooxidative properties of lipofuscin may be involved. We explored the effect of 568nm light on the autofluorescence intensity of flat-mounted human RPE slides, imaged using a fluorescence-AOSLO. The RPE slides were simultaneously exposed to 830nm and 568nm light of various powers and durations over a square ½ degree field. Pre- and post-exposure images were taken in a 2 degree field. Exposure to the 568nm light resulted in decreased autofluorescence intensity of magnitudes related to the intensity and duration of each exposure. In the subsequent 48 hours, partial recovery of the autofluorescence intensity was observed in the fixed tissue, implying that the recovery of RPE autofluorescence following light exposure is not entirely a metabolic process. Additional imaging and exposures were done on cultured, fixed, A2E laden RPE cells in order to explore the potential contribution of A2E photooxidation on the autofluorescence intensity decrease and recovery.