Immunoreactivity (IR) for 4-hydroxynonenal (4-HNE; red) in the retina following 670-nm light treatment and exposure to bright continuous white light (BCL). (A,B) IR for 4-HNE was faintly detected in the inner (IS) and outer segments (OS) of both untreated (A) and 670-nm light-treated (B) dim-reared animals (arrows). (C,D) IR for 4-HNE was more intense in the IS and OS (arrow) following exposure to BCL. (E) Treatment with 670-nm light prior to BCL resulted in a marked reduction in IR for 4-HNE (arrow), compared to light damage alone (C). (F) Negative controls showed no specific staining for 4-HNE following BCL exposure. ONL = outer nuclear layer; OS = outer segments.