You may be going blind because you're getting too excited about becoming lucid in the dream, and this is causing you to break the flow of it.
Make sure your eyes are closed when you attempt to project. If you still get stuck then maybe you should try and use another method.
A simple way to exit the body is to feel yourself standing up and walking towards the door, or the window. You probably will have to touch the things around you to gain vision, and when you vividly feel yourself there in front of the door or walking you'll be out. It is really about guiding your point of awareness. It should feel as if you're waking up as a ghost.
For more information on lucid dreaming go to: www.lucidity.com
You'll find some very helpful information there.
You could be being taught how to see a different way, attempt to touch somthing. I had a similar experience where I was some where really bright and could basically just see white around me. Then I attempted to touch something and noticed I could see more.
in the last week i've had two separate near-obe's that were almost exactly the same:
both times i was taking a nap in the afternoon. I became lucid in my dream, but suddenly as i did i found i couldn't see properly. i tried saying "clarity now" and focussing on my hands but nothing worked. I knew that i was dreaming but for some reason i just couldn't see at all. I was afraid of waking up. I found myself back in my body and tried to initiate an obe, but i found i was stuck. I could feel some vibrations with the ROPE technique but I couldn't get out at all.
so my question is, why am i going blind, and why am i getting stuck, and what can i do about it?
thanks,
ash