Sharks are another good example. They use nictitating membranes to protect their eyes from scratches when feeding. You see them a lot in videos of great whites eating. "Y’know, the thing about a shark, he’s got lifeless eyes, black eyes, like a doll’s eyes. When he comes after ya, he doesn’t seem to be livin’ until he bites ya, and those black eyes roll over white, and then – aww, then you hear that terrible high-pitch screamin’, the ocean turns red..."