Due to overuse of smartphone or laptop leading to severe dryness (computer vision syndrome) .you will have to learn how to work on laptop for long hours without giving discomfort to eyes, while working on computer number of blinking drastically goes down from  around 24 per minute to around 8 per minute causing severe dryness because blinking gives nutrition & lubrication to the eyes . one should look away from computer after every 10 minute & take rest for 10 minute after every two  hours,You should also use lubricating eye drops (Refresh liquigel)5-6 times regularly &genteal gel once at bed time .you should try to have normal blinking while working on computer.