Just jumping in to say that 'shimmering vision' was one of the first symptoms I got when I developed ME/CFS; after a virus, as a 20 year old student.
Eye tests always normal; ophthalmologist examination was broadly normal except an ultrasound showed that the 'slight disc swelling' I had was optic disc Drusen. Apparently a normal variation and nothing to worry about, I was told.
I heard about Irlen Syndrome or scotopic sensitivity and tried coloured overlays and lenses. The rose coloured overlay might have helped a very small amount but the very much more expensive, custom lenses weren't effective.
More recently I'm wondering if my symptoms are closer to oscillopsia? which is thought to be a vestibular disorder. I developed tinnitus around the same time.
My symptoms are a 'shimmering vision' that is present all the time in both eyes, sort of like a heat haze, images feel like they're not completely stable and solid, depth perception affected, sense of 3D vision compromised. It affects me most when reading, it's difficult to track the letters and follow lines of text. It's worse if I'm in an environment with a high allergen load, like house dust mites, and if I have a cold or flare up of sinusitis.
I think the University of Leicester in the UK were looking at vision disorders in ME/CFS but not sure if they found anything.