Do a circle with the freehand tool and paint it with the airbrush. I darkened the outer line of ehe circle. Paint the cornea white, but you have to shadow it in the corners to do that 3D feeling again. Because it`s round, not flat.
Let`s continue. The eyeball…
Do the eyeball with the airbrush – it`s perfectly round. And a small reflection. It`s made of three circles – the one in the middle has the highest hardness and the two on the sides havew lower hardness. Hope you know what i mean. The two circles are put over the one in the middle, so it looks more blurry.
I darkened the upper side of the green. Using the darken RGB tool. You remember… Then I something yellow at the bottom of the green and smudged it a little, so it doesnt’t look so sharp. Then do some highlight over it and lighten it so, that the middle of those pointy thingies 
is the brightest. I drew some more green circle in the eye and put brighter circles on top of them. Draw the eye-lashes. Don`t worry – it might look funny now, but when you resize it it looks great. I smudged around the eye a little bit too. The shadows and whatnot.
