How frustrating, but I guess it just shows that even Mayo doesn't have answer to every issue. If it were me, I would ask them who they feel is the preeminent eye specialist I could possibly contact based on what they have seen in your tests.

Here are some other major medical centers known for eye care: Massachusetts Eye & Ear Infirmary, Cleveland Clinic, University of Iowa Hospitals and Clinics, Johns Hopkins...

There are two other possibilities -
Go to this group on Connect https://connect.mayoclinic.org/group/eye-conditions/ and post a new discussion. Give it a title that is descriptive of the problem you have. Describe your symptoms and maybe share a little info about what has been ruled out as well. I'm guessing you will be able to find someone with a similar or related issue.

The other suggestion, if you haven't already tried - there is a group called the Phillips Eye Institute in Minneapolis. Many people I know have consulted them for highly complex eye issues. https://account.allinahealth.org/carenow/options

Have you asked your local docs for recommendations?
Sue