HMOX1 and retinal degeneration: Since light-induced retinal degeneration is related to oxidative stress [12,15,38,40], we assessed the oxidative stress markers; the retinal mRNA levels of Nrf2 (Figure 4G) and HO-1 (Figure 4H) were upregulated in the LE-with-vehicle-treatment group at 3 h; however, the levels remained close to those of the control in the LE-with-4-PBA-treatment group.