Thank goodness - that eye was freaking me out.
After getting a closer look, it seems we need to fill three basins.
There seems to be a contraption specifically designed to hold the prism, too.
...Nothing happened. This smells like a light-based puzzle.
Not that kind of light-based puzzle; more of a reflect-the-beam-with-mirrors puzzle.
There are two in the cave; one next to the peacock statue, and another being held tight by a petrified woman.
You'll need to direct the laser into the mirrors so that it reaches the prism.
Somewhere on the right side of the cave, in the path of the laser.
The holes in the rock around the mirror that you picked up are actually a useful hint here.
Push the peacock statue so it reflects the laser off the petrified woman's mirror.
Against the holes on the far-right side of the cave, next to the worm.
It may not be intentional, but I like that the holes imply prolonged lasering and / or repeated mirror usage.
The prism is powered - see if you can make sense of the symbols.