Refraction?

I've been thinking about refraction and how one of the professors I would TA for pointed out a major problem for the invisible man. If he was truly invisible, light would pass right through his eyes - and he wouldn't be able to refract light with his corneas to form an image.

Then I started wondering about fish - what's the index of refraction in fish? Is it different in freshwater fish versus saltwater?

"Clams with Laser Pointers" is the name of my 80's cover band.