OK Don, I did some research. It appear the retinal pigment is chromatin base not melanin based. If there were no pigment (this may not be the correct term?) of any type in the retina, they would not be able to see. These are based on proteins. Sorry I forgot which proteins.
I had a little bio, and I get the jist, but I really do not know more. I just have a knack on digging up odd info. I hope it 1, makes sense to you, and 2, it helps.
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Thanks for reading.
Big Tom

