And if any animal is going to get crusty eyes, it would be the notoriously lethargic sloths.
"Nature has a way of adapting so they probably have something that keeps the crust from building up.".
However, researchers have found that sloths have such poor eyesight that they hardly use it for climbing or foraging.
This is where things get a little more complex, because there are two groups of sloths: three-toed sloths and two-toed sloths.
Their default position is a tight strong grip, and they must exert effort to open them.
These appendages give the sloths a very fine sense of touch, which in some ways compensates for their poor eyesight.
"I'd be a little concerned trying to clean up the crusty eyes with those claws," says Leslie Da Lie. »