Kohunlich: Pyramid of the Masks [December 31, 1997]
The markings in the eyes are most probably the Mayan hieroglyphic sign "kin", meaning sun/day. The sign itself is a cosmogram, which basically is a map of the directions (the four-leafed look to the symbol is actually marking the four cardinal directions and the center). This sign would make sense on such stucco masks, which depict sun deities.
Information courtesy of Dave Hixson, Tulane University