Spending hours slumped over a keyboard under the same artificial lighting, day in and day out, will harm your productivity more than help it.
If possible, take a refreshing break outdoors in nature. Countless studies highlight the benefits of being outside.
Even just looking out of the window can freshen you up and give your eyes a necessary break.
If going outside isn't an option, simply looking at an image of a natural scene can have similar calming effects and help you focus.