Have you seen the tuts of Pixolator and Glen Southern ?
Pixolator eyes tut (in the post3 some cool links about eyes)
Glen eyes tut
Else you can create intricating spheres 3D or part of them with different intensity of RGB for similate transparency 
Pilou
very very nice.
Congrats for thr toprow. Its a very fine work u made and so detailed
Keep it up 
hey Arturo,
good to see ya here man and kickin butt on zbrush!!! looks great!!!
need to get back over to the lab and start posting those sculpts of yours!!
Super work you did.
absolutly fantastic!
but you all might know that da vincei died at the age of 63 not 120…
very nice, congrats for the top row:D
nice model, but i think the viens and livar spots might be a too promenant try washing them out slightly giving them a more naturalistic look.
Buenísima imagen. Aunque creo que le falta la mirada soñadora de su autoretrato. Por cierto, ¿le pegaba al tinto el maestro Leonardo?
i would leave that paint doubt filter out though…
The skin texture is very nice. I have only 1 crit to say, he looks nothing like Da Vinci. Other than that I like it.
Finally I had time to finish the proyect, it is funny all the critics about the fatures, this last one it is the same model, I only have change the perspective, and of course the beard that now it is better,
the other one only ws a test as I said.
Thank you very much for all the answer, I was thicking to let the proyect flow, but all of you(good and bad critisc) make me get something better.
Arturo 
with the paint daubs of photoshop.
Hope you like,Arturo 
ANOTHER
TOP
ROW
!!!
nice eyes
Pilou fan of Leonard
very nice work! how did u do the hair??
Thank you to all.
About the hair, I made it in photoshop.
I began with a grey yellowish, and made hair by hair, drawing with the direction, after that I made the same with black(more were would have to be the shadows, and finally with the bright grey(more where the highlights).
I copy this layer and duplicate one or two times depending on the amount of hair desired. merged the three layers
Then liquify filter if it is necesary change the waves.
After that I use to copy this new layer.
Now I adjust the brighhtnes and contrast to make a darker copy and less contrasted.
I erase the upper layer(and brighter), where i want to get more shadows.
hope this help.
Best wishes,
Arturo
I like the modelling of the head.
But for the textures, I think it has definitely too much bump, even for an old man. And the skin color is a little bit too red. Also the hairs are too thick.
Other than that, great work.
Yes now it does resemble him more and i like the features of the face. But i must agree that the texture has too much bump on his face, and now it looks like he has a rash on his face. Its a little too red in my opinion. I loved the first texture you posted in the beginning. That was really nice looking…
Tweak the textures a little more and tone down the redness, and you will be all set.
hope that helped…
Cheers