C.J. Cherryh's "mri" aliens were humanoid, but they weren't completely human-formed. Their eyes were adapted to desert planet ecologies, with sand-proof eyelids and a third eyelid called a "nictitating membrane." On earth, various birds and other creatures have them but humans do not have one, at least one that works. The third eyelid protects the eye against irritants, sand, and harsh atmospheres. In the "Star Trek" mythos, Vulcans also have a third eyelid which figures in an episode where Mr. Spock believes he has been blinded but has only had a previously unused third eyelid close over his eyes.
The mri of the warrior class masked their faces in public, showing only their eyes and part of their facial tattoos. Their headdresses also had a thick plastic visor which would cover their eyes during battle. Nowadays our visual world is full of fierce black-clad desert warriors who mask their faces, such as the members of the "Islamic State of Iraq and Syria." In a lot of ways, though I shouldn't admit I think this, terrorism is a form of theater, complete with costumed identities and pre-written scripts and scenarios. What would a science fiction writer do as Secretary of State?
"Mri Eyes" is gouache on thick watercolor paper, 7" x 5", fall 1981.