Eye strain with ipad pro and 6s

I have had eye strain problems with 6s last year and then I sold it and continued with my 5s. Now I brought the new ipad pro 9.7 and again the same issues with eye strain, headaches.... I am ok with my 5s and ipad 2 now that these models are out dated desperate for a change. I know many people had issues with the retina displays. Has anyone come up with a solution. I have tried all possible solutions found on web like reducing brightness, reduced motion, increase contrast.

Even the doctor couldn't fine any problem.