I need guidance in understanding physically accurate eyeballs

I have created this character and brought it into Unreal Engine 5.
I am very happy with the model and hair & skin materials.

I am greatly struggling with the eyes. I have created anatomically correct eyes and traced medical drawings, complete with:
melanin, sclera, muscles, cornea, lens, and vitreous humor(the vitreous solution is in this material too).

I am using individual materials for each of the eyeball components so that i can control the individual IOR. And each of the transparent IOR’s are anatomically accurate.

Is there an Unreal Engine Tutorial that exists… like a REAL, great one, that explains Unreal materials for the eyeballs? I have watched many tutorials as to how the eyeball is ‘faked’ in unreal… but again, I’m going for physically accurate. I dont want to believe that all im supposed to do is wiggle sliders to make everything ‘look right,’ because i can do that… but it wont be correct.

Additionally, they look SO DIFFERENT when the camera is up close vs when the camera backs off from the subject. I’m very lost.

The eyeball model that is attached was rendered in Max. it does EXACTLY what i want it to do. I KNOW i can do this in unreal, but im failing.

im hoping a pro who understands arnold, zbrush, and unreal pipelines may be able to help me.
Im having some serious disconnect issues from one piece of software to another.
thank you for your assistance.



Additionally, I have no idea why this is happening:
Characters IOR Scales?