So here's the deal:
In a D&D-fantasy-style world, the continent of Archaon is inhabited by a wide variety of elves, whose physical characteristics vary based on their dwellings. The forest elves are more agile and can camouflage with the trees; the water elves have larger lungs and can swim more easily; et cetera. Some elves, however, decided to go into the caves, and never came out. Over the course of a couple hundred thousand years they evolved. They stopped developing pigments in their skin (unnecessary), they developed larger ears (to hear burrowing creatures), and their eyes had to become more receptive to light.
This is where I'm stuck.
I've done some research into the eyes of underground creatures, looking at things such as the tapetum lucidum, but I'll confess I'm not very good with biology. So, consider the following particulars:
- The Cave Elves live deep underground, where there is very, very little visible light
- Most light that they do view is in the blue-green spectrum, thanks to phosphorescent mushrooms and creatures
- They began with "standard" eyes, with a pupil, iris, etc.
- They came to the underground by choice, perhaps due to a hostile surface that was more hospitable underground.
- The caves of Archaon are fairly well stocked, with various plants (fungi?) and burrowing animals (such as large worms) that would provide supplies for the cave elves.
- Most objects in the world give of a very, very weak "aura"-type energy that could be considered part of the electromagnetic spectrum
Knowing this, what are some of the most likely biological night-vision evolutions the Cave Elves might develop? I've considered a few options - cat- or owl-like eyes with the aforementioned tapetum lucidum, albino-like, solid red eyes due to not requiring pigmentation in the eyes, or just plain bigger eyes.