If you import via native and use the proper light thru trans options...I haven't seen a problem since 5.03, I think. If you search the forum you will see it has come up alot. I think native is the best way to go personally for most situations because you can save and tweak your shaders etc...Also, some textures for cornea's use a map in the color channel... in general you want to remove that and tweak the corneas like the other textures.

No need to think outside the box....
    Just make it invisible.