It causes canthaxanthin retinopathy. Essentially deposits of canthaxanthin in the retina. Seems that people who took supplement canthaxanthin for self-tanning purposes were the folks to had issues with canthaxanthin retinopathy. Probably not an issue for those who consume a bit in food as an additive.
Here's Google on it: https://www.google.com/search?q=canthaxanthin+retinopathy