It turns out that what I had was a migraine aura without the headache (and I'm obviously very happy about its absence).  At first I was worried I was having a stroke.  While watching TV last saturday I noticed a small spot in my field of vision where I couldn't see.  It got bigger and bigger.  It wasn't light or dark colored, it wasn't blurry.  I simply had no perception there.  Then I noticed a faint, brightly colored area around the central spot.  The whole anomaly grew a bit until was big enough to cover a person's face at about 5-10 feet (although it was just right and down from the center of my view) and then for a few minutes I lost about 20% of my peripherial vision on the right side.

and...this is about what my migraine aura looked like