In short, each eye set comes with a set of pre-made "highlights", in two sets of three strengths each. There's an iris low-light, an iris mid-light, and an iris highlight. This is the iris highlight with the Scarlet eyes:
|(from the Avatars album; the iris highlights)|
It's very subtle. I snapped this photo on default Midnight, so trust me, while it is visible, it's more in the nature of a gentle glow.
There's also a set of socket lights, in low-light, mid-light, and highlight. This is the socket highlight with the Scarlet eyes:
|(from the Avatars album; the socket highlights)|
These are far from subtle, but keep in mind I'm also showing the effects on the eyes at full strength, with the default Midnight setting. There are two other included socket light levels.
And...that's about it. Anyone who's actually read through each one of these deserves a medal, or something.
(Dress is from FallnAngel Designs, the "Rhy" dress in Purple, acquired in the Halloween hunt [now over]. Hair's from Sugarsmack, Kai hair in Ginger-Berri [Hair Fair 2012]. Horns are Rue's "Shaman" horns in TrickOrTreat, part of the Eclectic Desires L$10 skull hunt [no longer available]. DV8 made the Danse Macabre boots in Black [no way to acquire them, DV8's off the grid]. Skin's still from MoMo. The forehead jewels are from the Arachnos skin set at Fallen Gods [it comes with spider back-arms and the Arachnos skin as well, and it's no longer available].)