We might think that guitarfish had a huge problem. A brief article in Science says:
“Like sharks, the giant guitarfish doesn’t have eyelids that close all the way, so it can’t blink. That might guarantee a win in a staring contest, but it does pose problems for eye protection in the sandy, tropical waters where the creature lives.”
But that is by no means the end of the story:
“So when thrashing prey kick sand or bits of coral its way, the guitarfish protects itself with an eye-catching method: retracting its eyes almost completely into its head, leaving a craterlike depression. Now, new research shows that guitarfish can thank a specialized eye muscle for that ability. Using high-speed video, researchers found a guitarfish could sink its eye nearly 40 mm. That’s almost as much as the diameter of the eyeball itself and likely more than any other vertebrate, the researchers reported online before print in Zoology.”