Marcin Bartoszewski: I created the Diffuse Amount layer by baking the Concavity Type Occlusion. The final result is a map where the indents of the fine details are darker, similiarly to a cavity map generated in ZBrush.
adrencg: The refraction of the cornea and the anterior is set to phisically accurate values. Behind the iris, there is a concave light absorbing surface in place of the lens. The eye has SSS. Using this solution can achieve an optimal result, with regard to render time/lifelikeness.