In today's age, we look at computer screens and through glass far too much. I have been recently practicing the following exercises and have noticed an improvement in my eyesight over just the past couple months.
One exercise was to count the leaves on a far away tree. With meditative patience they would focus in and count hundreds of leaves at a time. (This is a good one to practice in the fall since the leaves are changing colors and you may be staring at leaves quite a bit anyway.) Start up close with some leaves that are easy to make out and count 50 of them. With patience, slowly pick trees that are farther away from you and then slowly increase the number of leaves you count. Work your way up to 200 which will give you a good amount of time with your eyes focused at a distance. Do this once daily.
Another exercise is to focus on an object very close to your face. I usually choose my hand. Get it as close to your eyes as you can while retaining a good focus on it. Look at it for about 2-3 seconds after you've fully adjusted your focus on it, and then pick another object that is more than 20 feet away. I generally pick a leaf on a tree or something else that has some fine detail that will allow me to really focus on finer and finer detail. If you pick a flatt wall or something that doesn't have much texture or detail it will be hard to focus on. Again, look at the object for 2-3 seconds after you have achieved a good focus. Go back and forth between these two objects about 20 times and do this exercise daily.