What is the purpose of black pigmented skin around the eyes?

those are not bags under my eyes from sleep deprivation… Meerkat photographed at Happy Hollow Park and Zoo, San Jose, CA
Is it really to reduce glare from the sun for diurnal animals that are running around in brightly illuminated landscapes?
If so, then why do these two nocturnal hunters have dark masks?
![By Ltshears (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons](https://bybio.files.wordpress.com/2013/09/528px-black-footed_ferret_001.jpg?w=584)
Black-footed Ferrets hunt prairie dogs in their burrows at night. By Ltshears (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)%5D, via Wikimedia Commons

Racoons might be raiding your garbage can or dog food bowls left outdoors in the late evening hours. From: http://en.wikipedia.org/wiki/File:Raccoon_(Procyon_lotor)_2.jpg
Any ideas?
You’ve stumped me, Sue. I don’t have a clue.
I can’t even guess. I wonder if anyone really knows why.
I’ll have to do some research on this!
I had always thought it was to camouflage the eyes. Eyes can be seen be prey and predators. Even the nocturnal hunters are hunting sharp-eyed prey or being hunted by the same. What do you think?
Sounds plausible. I think what nocturnal hunters would really want to hide would be their mouths, not their eyes. I wonder if the dark patches absorb stray light rays and help animals focus in dim light, the same way dark markings around the eyes protect them from high solar input in the daytime. There is probably some study of this somewhere in the science literature. I’ll look it up when I get home. Thanks for your input!
I think I heard somewhere that it reduces glare around the eyes.