It was requested a couple of times, and I didn't feel like doing commissions so I just made a tutorial.
No writing or anything cause I'm too lazy, I'll try to explain it here
STEP 1 : Outline the eye.
STEP 2 : Color in base
STEP 3 : Add a darker color in that design
STEP 4 : New layer, luminosity, marker tool
STEP 5 : Add another darker darker color
STEP 6 : SPARKLEZ!
STEP 7 : New layer, luminosity, add shines.
STEP 8 : New layer, line out a half-circle with white colored pen. New layer underneath that. Color in half-circle, then lower the opacity. Combine layers, set as luminosity, and lower opacity to your liking.
STEP 9 : New layer, multiply, shade a bit.
STEP 10 : Color lineart, and you're done.