This issue seems to be notorious for DHS eyes and ray tracing. It's a problem of eye and cornea mesh being too close to each other.
Now, I do not know anything about Omniverse and how it does render, but in iClone and CC same problem appears to be with Iray.
There are 3 ways to handle it with Iray. I am not sure if there is a way to tweak render engine in Omniverse, but the last method (with displacement map might work if Omniverse supports it).
Otherwise there is a ticket already opened in FT for RL to fix the issue:
https://www.reallusion.com/FeedBackTracker/Issue/Circular-Artifacts-on-sclera-of-eyesSo just FYI