I'm so glad I found this post! I've been suffering from dizzyness and extreme headaches for years. It started with computer screens. I found out I couldn't work with screens with a refresh rate lower than 75hz. But then I got an Android Tab and felt the same as with the computer monitors. Starting with a really tired feeling in and above the eyes, noticing a subtile flickr and then the headache and sometimes nausea comes in. The headache doesn't go away with anything, just a night sleep let it go away.
Last Summer I ordered a new computer screen because my old one (Acer, non-widescreen) got a bit too old. As I'm doing lots of photo-editing, it's useful to have a good screen. I placed and connected the new screen, put it on and felt it immediately. Unfortunately the refresh rate couldn't get higher than 60hz. After informing I knw now that most of the new screens you can buy these days, do not have higher refresh rates than 60h.
Then I started savind money for the iPad Air, which I wanted so badly. I bought it last februari and after working with it about 10 to 20 minutes, the noticing of flickering and headache came. I returned the iPad to the shop. I was so frustrated. Now I really want to buy the iPhone 5S. I've been seeing it in shops and I notice the screen 'feels' different to my iPhone 4S, which I can work normally with. There is a change I will experience the same problem with the 5S as with the iPad Air, I really hope it works out this time, because otherwise it would mean it would be very hard to buy a new phone ever again.
I am visually impaired, which means I have a sight of 5% plus nystagmus and my right eye is only 3%, which causes it to be unable to focus so my eyes aren't moving equally. I always thought the sensitivity for this kind of screens had to do with the fact I am bad sighted, or maybe even the nystagmus. Reading this post makes clear for me this isn't a problem I am suffering from by myself alone plus, it's not directly related to my visual impairment. Even though I didn't find a solution here, I'm glad to meet other people who are suffering from the same problem. In my case it's purely the screen, so the LED problem. I have never noticed problems with led light before, but it comes up on computer screens and tablets/smartphones.