i am 65 years old, male, generally good health. For at least 10 years, I have occasionally (maybe once a month, once every few months or as frequently as every few days) experienced brief periods (10 minutes to a couple of hours) during which my field of view is interrupted by "blind" spots or areas. I have never noticed the effect in only one eye. Sometimes the effect is just an ill-defined blank area and other times there appears to be a very well defined shape (like a crescent Moon shape) with either pulsating or fixed black and white patterns. These areas of interrupted vision have never been in the center of the area I can see, but are off center ranging from just a few degrees to as much as 60 degrees off-center. I have never experienced any pain or discomfort associated with this sensation. Your questions or comments will be appreciated.