My eyes are tired and stressed during exams. What can I do?

Rest. Sleep more before the exam. Have the correct glasses/contacts if needed. Take breaks looking away to interrupt accommodation.
20 20 20 rule. Relax your eyes! Every 20 minutes, look at something at least 20 feet away for 20 seconds. This allows relaxation of the focusing and eye alignment muscles and makes you blink - it works wonders!