Its quite unpleasant for sure! I'm very interested in what the research on the long term effects will be. After covid I found I had the following new problems: terrible anxiety (fortunately fading), joint pain (might be getting better but hard to tell), visual distortions (which got a lot worse after consuming hallucinogens), and a reduced tolerance to LCDs (but as I say that was getting worse before covid), and fatigue (fortinately relieved with caffeine and sugar).
Based on these symptoms, the best explanation I can come up with is that covid has triggered an autoimmune reaction. Where my immune system is attacking is serotonin receptors, receptor 5ht-2a best fits the symptoms. It is associated with migraines, visual distortions, and joint pain.
Getting back on topic
I've increasingly found that my food allergies are worsening my tolerance to LCDs. Not saying that's causing your problem, but I am saying you might need to think outside the box. If you can't find any help with the suggestions already made, it might be worth keeping a log of your screen tolerance to see if there is any fluctuations. If there is, logging your daily activities might yield some correlation.