Light damage as a model of retinal degeneration.

The induction of retinal degeneration by light exposure is widely used to study mechanisms of cell death. The advantage of such light-induced lesions over genetically determined degenerations is that light exposures can be manipulated according to the needs of the experimenter. Bright white light exposure can induce a synchronized burst of apoptosis in photoreceptors in a large retinal area which permits to study cellular and molecular events in a controlled fashion. Blue light of high energy induces a hot spot of high retinal irradiance within very short exposure durations (seconds to minutes) and may help to unravel the initial events after light absorption which may be similar for all damage regimens. These initial events may then induce various molecular signaling pathways and secondary effects such as lipid and protein oxidation, which may be varying in different light damage setups and different strains or species, respectively. Blue light lesions also allow to study cellular responses in a circumscribed retinal area (hot spot) in comparison with the surrounding tissue.Here we describe the methods for short-term exposures (within the hours range) to bright full-spectrum white light and for short exposures (seconds to minutes) to high-energy monochromatic blue or green light.