Quote - Mathman, why are you using blue tinting in Alt_Diffuse?  Is this for the skin?

Good question. Short answer is, I don't know. In any event, I have now fixed it, but the problem persists.

Quote - Does the eye cover involve a refract node? If so, do you have enough raytrace bounces (2+) to get through the lens and the eye cover?

BB, what do you mean by the eye cover ? ... I tried rendering with more raytrace bounces, but once again the problem persisted.