I always liked sitting close to the tv set. That was before giant flat screens were available. It is said that there is no direct evidence, however that sitting close to the monitor harms your eyes. It may be a sign, though, that you are near-sighted and should see an eye doctor.
Reading under dim light is not dangerous either, but expect to feel some eyestrain. Also, staring at a computer screen for long periods of time when surfing or playing video games will dehydrate the eyes and cause eye fatigue. That’s because our eyes blink less. So every once in a while, give your eyes a break. Glance up, gaze across the room, or look at far away objects. At Least Every 20 minutes would be a good interval.