A2E (N-retinyl-N-retinylidene ethanolamine) is a well-characterized bisretinoid fluorophore and toxic lipofuscin pigment that accumulates abnormally in the retinal pigment epithelium of the human eye, heavily implicated in the pathogenesis of age-related macular degeneration. Its chemical formula is C42H58NO+, yielding a molecular weight of approximately 592.92 grams per mole. Researchers study its precise molecular mass to design therapeutic interventions aimed at blocking its formation and protecting vision.