Occasionally when I focus on something for a long time, such as reading or watching a lot of tv my vision gets slightly double. For example, if I am reading something from far away such as credits to a movie the name of the person will be doubles directly above it. I also have occasional difficulty while attempting to read things far away. My eyes are also extremely light sensitive. I am curious as to whether this could indicate that I may need glasses or is simply due to focusing for an extended period of time.