The eye from the lab is more complex and got a second mesh for cornea and a iris hole. The built in eyeshader requires a simple mesh without that hole as it fakes refraction. I don’t think it’s possible to use the builtin eyeshader without replacing the eye-mesh. I did something like that already successfully in the past for a makehuman mesh… however it did not contain any shapekeys (the current mesh from the lab includes them to look up/down/left/right). You have to recreate those shapekeys if you replace the mesh (for example with an export of the content example mesh).