Eye pain after few minutes of watching.

Doctor suggested me power -.5 degree 175 cylindrical. When dr was doing eye test then intially words were visible correctly from the given power in my right eye when my left eye was closed,but after few seconds even on power few words started viewing blurry to me. But when i asked my dr about it he told you have problem of dry eyes and eyes have become watery in few seconds thats why i am seeing little blurry now. I am in confusion what to do now. With both eyes open i don't find difficult but with left eye closed,i feel difficulty in seeing from right eye. Should i go with zero power in left eye and -.5 degree 175 cylindrical in right eye. As my most of work in on phone laptop so i will take blue cut lenses coating. I used to study 8-10 hours and feeling headaches and eye pain. Plz tell what to do