#HELP

Hi everyone, I have now taken 3 practice tests on Khan Academy and I find it really hard to stare at the screen for so long with such a short break. My eyes start to hurt and it becomes really hard to focus after about an hour. I have been taking those rather than printing out the old ones because I want to get used to taking it digitally. Does anyone have any suggestions on what to do to release the tension while I'm taking the test? The 15 minute break helps but as soon as I go back to the screen my head starts hurting again.