ABCA4 and Abnormal retinal morphology: While we find that fenretinide induces apoptosis in ARPE-19 it has also been shown to effectively block the formation of lipofuscin fluorophores such as A2E in the RPE of Abca4 knockout mice47 and so has been proposed as a therapy of lipofuscin-based retinal diseases such as Stargardt disease47 and AMD48, in spite of its known toxicity and use as a chemotherapeutic 22–25.