I don't have an iPad but an iPhone 11, but I feel the same way.
I have been able to use my iPhone 11 for almost a whole year without any problems.
For a few weeks now, the smartphone has been virtually unusable for me. After a few seconds of looking at the screen, I get extremely tired eyes and a slight headache. It feels like I've been using the smartphone for several hours at a time when writing a single text message.
These symptoms have come on suddenly. I would have timed them pretty well to the update from iOS 15.1 to 15.2. However, I cannot completely rule out the possibility that it also occurred with a version 15.1.
Currently, I have no choice but to use the smartphone as little as possible and do everything possible via my Surface. Since I do not have these complaints here.
Unfortunately, I have saved my SHDH Blobs from previous versions, so I can downgrade the iOS.