Not too sure what to advise, except try to take it one day at a time, live for the present. There is no point worrying about something that might never happen. Either that would drive you miserable and/or you would waste precious time by spoiling the present. I also know it's easier said then done but... one can only try!

What might also help calm these irrational or unjustified fears is to counteract them with concrete/objective facts or knowledge. For instance, can you not have it checked to see whether it is simply your eyesight? If you *know* what is happening, you might be better able to deal with it. Plus, that would reassure you.