All screens I've used before are LCDs. Considering now an OLED option on a smartphone. However, there's lots of info about harmful effects of OLED on eyes, among those:
PWM flicker, which, while not immediately noticeable, might affect eyes negatively.
Infinite contrast of OLEDs, which is also something that our eyes might not like (like, white text on black background or vice versa).
Pentile subpixel arrangement vs rectangular LCD arrangement. Might negatively affect text clarity etc., and thus cause extra eye strain due to eyes being unable to focus (?)
Not sure about all of the above myself. I'd agree with #1 though, as long time ago I've been working on a laptop that had some low quality PWM implementation that flickered at 90Hz, and it's been terrible.
What truth is there to the above statements? Is there any research available to validate or disprove them?