Prolonged duration of studies and near work put lot of stress
on ciliary muscles and extra ocular muscles which can cause fatigue
of these muscles. In such situation even small refractive errors and convergence insufficiency due to weakness of muscles cause even more eye strain
. Stress increases all these symptoms. Eyecheckup, nutritious and vitamin rich diet, scheduling your studies such that you take a break every say 20-30 min for few minutes and allow the muscles to relax will surely help. You may due relaxation and strengthening exercise.