Editing Ianthina (section)

== Vision ==
Ianthina are nocturnal, and their eyes are adapted to pierce the dark depths of the ocean through long months of arctic night by the thin light of their lumens, and thus are extremely light sensitive. Their irises can come in any color and tend to be relatively large, to maximize the size of the pupil in the dark, and their scleras are black. Their irises are capable of expanding and contracting to an extreme degree, either expanding so much to leave the pupils mere pinpricks, allowing them to function in slightly brighter environments, or contracting until the iris itself is scarcely visible. 

Star- and W-shaped pupils are by far the most common in Olitskur, as they are the most effective at seeing through the dark. String-of-pearl and ray pupils can't expand as wide, making those who have them (by ianthina standards) borderline night blind and struggle to navigate outside cities. These types of pupils are the most common type in the Southern Enclaves, as those ianthina live closer to the surface in generally brighter environments. Bar- and heart-shaped and pupils are somewhere in the middle: they can handle light better than star-shaped, though not as well as string-of-pearl, and can handle darkness better than the string-of-pearl, but not as well as star-shaped.

They have a third eyelid, to protect the eye while swimming fast and to clear away any debris.