On a personal note:
I have retinal vasculitis and had a central retinal occlusion at sea level in 2007 that left me functionally blind in that eye. During the following three years I climbed many mountains up to 29,035 feet and never had any HAR. I know because every time I returned I went straight to my retinal specialist at UCLA's Jules Stein Eye Institute.
I know it happens, just telling my experience.
