Cancer Eye: Treatable But Heritable
Dr. Ken McMillan
The third eyelid is an extra "lid" all nonprimate mammals have. It’s on the lower inside of the eye and can move from that point diagonally upward. It helps keep the cornea clean (think "windshield washer"), produces tears, contains lymphoid tissue that produce antibodies to fight infection and protects the cornea from injury. It’s also a common site, along with the lids and the globe, for cancer eye.