I had that fear too. You should work on it. It is not only a fear of loosing your eyesight, it is usually something a bit deeper.
I had a very strong episode of it when instead of a practice on court the basketball coach took us outside to run at at the beach, I didn't bring glasses with me and just couldn't see anything in the dark.
Maybe you had some sort of trauma related to your eyesight or someone in the family who went blind or something..... You should really talk to a professional if you feel it is more that 'not wanting to be blind' kind of fear, like if you feel it has a bigger impact on your daily life.