2. The shape of viri maybe illustrates how the 'eyes' representing two past segments of time no longer are present. Only 'empty eye-sockets' are left:

The glyph should then be imagined turned 90º to the right, i.e. in the opposite direction compared with Rei glyphs. Probably Rei glyphs are male in character while viri are female.

The eyes are intimately connected with light, they are organs which in a way create light:

"Fig. 2, taken from the Madrid Codex, a Maya document written shortly before the conquest, reflects the central role of astronomy among the civilizations of Mesoamerica. It shows an astonomer observing the stars. Seated in his station, he seems to be plucking them out of the sky with his extended eyes. The skywatcher is surrounded by hieroglyphs and Maya numbers which presumably relate to his astronomical secrets." (Skywatchers)

Without eyes you are blind, as if in total darkness.