Mice were dark adapted overnight in a darkroom equipped with a red light source during the experiment. Before applying light to each eye, the light intensity from the Micron IV mouse fundus camera was measured using a light meter (Fisher Scientific, Hampton, NH, USA; Cat # S90199) to ensure that equal illumination was provided to all eyes. Each mouse was anesthetized, one at a time, and the pupils dilated as stated above. We applied GenTeal gel to eyes to prevent corneal dryness during the length of the experiment. A single intraperitoneal injection of fluorescein (100 µL of a 1:5 diluted 10% fluorescein solution) was administered just before the camera was centered on the optic disc head and focused on the RPE. The desired light intensity was then applied to the retina as described previously.34 (link) In brief, after a 4-minute delay after the fluorescein injection the light intensity was increased to 45K lux and continued for 3 minutes (a protocol we called FA 3@4) while monitoring that no changes happen in the fundus orientation during this time. Mice were kept under normal lighting conditions after the light procedure.