A:Answer It is a personal choice. We have 50inch TV, we watch it comfortably from about 10 feet .
For more details take a look at https://en.wikipedia.org/wiki/Optimum_HDTV_viewing_distance
If you are worried about your eyes, then make sure you don't stare at tv, look at other objects in room, do not watch in completely dark room, keep blinking your eyes so that eyes will be moist.