I will try to address the questions and ideas people gave. Also, I want to thank Steelcan, DRietz, and Hot Potato for your compliments on trying to solve this the right way and being thorough.
I do plan on trying a long ride with goggles that protect my eyes from the wind. I currently use Trifosi cycling sunglasses. They wrap around a bit, but do not fully block the wind. The first 3 times this blurring problem happened, I was riding in the summer time (temps in the 80's). This last ride was a very cold, windy ride (temps ranged from the high 20's to the mid 30's throughout the ride). The problem's onset was much earlier than normal.
Before I started cycling, I worked out at the gym doing aerobics classes, jogging, and boot camp style classes. I usually worked out for 1 hour, (sometimes 2). I never had the eye problem. Now that I ride, I can see that my weeknight mt bike rides (2 hours) do not cause the problem. Probably, because I'm not going as fast and there's less wind in the woods. My weekend mt bike rides of 3-5 hours do not cause it. (Although all mt bike ride in the winter have caused a small amount of halo effect around the headlights when I'm driving home). My weeknight cycling rides of 2 hours do not cause the problem (30 miles). My weekend cycling rides of 50 miles in the summer have never caused the problem. The problem only happened on summer cycling rides of 65 miles or more (symptom onset at 60 miles) and on this one wintertime cycling ride of 65 miles (symptom onset at 40 miles). So, my conclusion is that the faster speeds of cycling cause the problem while the slower less windy mt bike rides do not. Also, the cold temps make the problem worse.
When the blurriness starts, and I stop riding, the problem goes away in minutes. When I continue riding for 20-40 miles, the problem worsens gradually as I ride. It lasts a couple hours after I stop riding. A strange thing is that if I don't stop riding it's not that bad. I can still see to avoid potholes. If I stop for 15 minutes for a break and then resume, the problems worsens quickly. That's when I got so blurry, I couldn't see cars and I rode through huge potholes with no warning. When it's that bad, the problem still lasts 2 hours after I stop.
I would love to do a ride and immediately have my blood drawn and tested for sugar levels. I'd also like to have my blood pressure taken post ride.
I looked up myasthenia gravis and optic neuritis. I don't think it's either of those because I don't have any of the difficulty speaking, drooping eye lids, or head falling forward associated with MG or the eye pain or vivid color loss associated with ON.
I am going to schedule an appt with the second specialist. I'll plan another long ride to make the problem happen. I will do everything in my power to find riders to come with me. It's hard because it'll have to be on a weekday. I had a rider lined up for last time, but he ended up getting hurt and couldn't ride. I am planning my next route to be 30-40 miles to get the problem started. I will then do a planned loop of 2 miles very close to the doctor's office. I will repeat the 2 mile loop as many times as I need. This way I'll be close to my stopping point when the problem gets bad. I'll look for a loop where I have the right of way with the traffic (all right turns).
Thanks to all for the input.
I'll keep you posted.
Angie