I just had to share this as I’m not sure if it’s a coincidence or not but I’ve had ocular migraines very rarely since I was young (probably one every couple of months), sometimes followed by a horrible headache, but always followed by the general horrible grogginess feeling.
Anyway, a couple of months ago I started getting them almost daily, absolutely horrible. After some googling I found a random Reddit thread that said to turn all the ProMotion off your phone if you have an iPhone 13 or more.
I then realised a started getting them more exactly when I upgraded my old iPhone 12. I since turned off all motion settings and have had none since.
I just wanted to share in case it helps anyway else! Just go to Motion-Accessibility and turn off the motion. I don’t really understand why but it really has helped!