There are several papers and theses (including this one about the Greenland shark http://www2.bio.ku.dk/bibliotek/phd/Julius%20Nielsen.pdf http://www2.bio.ku.dk

There are several papers and theses (including this one about the Greenland shark http://www2.bio.ku.dk/bibliotek/phd/Julius%20Nielsen.pdf http://www2.bio.ku.dk/bibliotek/phd/Julius%20Nielsen.pdf) looking at the isotopic profile of the different layers of fish eye lenses, down to the embryonic nucleus. Maybe all those researchers are onto something. Or maybe they are all wrong. I have no dog on this fight anyway.