Eating right is a good part of the answer - nutrition does have an effect on the health of your eyes. Another thing is lighting, mentioned below as well. Setting back from the TV a reasonable distance is important as well. But as far as improving your eye power - keep in mind, your eyes are muscles too.
I taught competitive shooting for several years. Eye acuity is extremely important for that sport. Exercising your eyes helps improve acuity so you see things better - although not to be confused with vision - actually being able to see.
One exercise is choosing something on the wall - like a picture. Look at the middle of the picture, then 2" up from the middle, then 2 inches down, the four inches up, then four inches down, and so on until you are (just moving your eyes) looking a foot up, and a foot down. Now do the same 2 inches to the right, then two inches to the left, then four, then six until you go out a foot.
Another good exercise is lying on your back, put a ceiling fan on slow and pick out the end of one of the paddles. Concentrate on that point as it whirls around and around making your eye alone move to keep up. If you can reverse the direction of the fan, do so for a like amount of time - just a minute or two.
These are great exercises for your eyes and can actually lessen the strain you are describing.