Eyes can easily get tired when lack of rest. Once they work for more than one hour, they'd probably get tired.
So you need to have a break every hour, or you can simply close your eyes for a while, or massage them.
Food with vitamin can be helpful as well. You can eat vitamin pills as supplements.
Hello, it is very normal for your eyes to get tired if you keeping reading for a long time. Because the eyes have muscles which can control the movement of the eyes, if you keep reading for a long time. your eye muscles will keep working and do not have enough relaxation, so you will feel tired.
Well, it is possible to have tired eyes when you have reading, especially reading lasts too long. Generally speaking, when you have reading, it will make your eyes focus on the small spots for long time. And that will just increase the eye pressure, leading to eye strain. Finally, your eyes will feel stressed and tired. So you should not have reading too long time. Also, to relieve your situation, you can just have some eye exercises. Also, some eye drops can be effective too.