1. A method for diagnosing a condition of an eye, the method comprising: projecting light at the eye; recording lipofuscin fluorescence from a retina of the eye to form a first image of the retina; processing the first image to make an image clarity determination regarding a level of conformance of the first image to at least one image clarity criterion; based on the image clarity determination, performing a step selected from the group consisting of: concluding that a cataract is present in a lens of the eye; concluding that the first image cannot reliably indicate macular pigment content of the retina; and calculating a macular pigment content of the retina.