@croydon - It does really depend on the circumstances. In that case I would definitely have gone to a doctor to make sure everything was all right. Even if your vision comes back halfway through the trip, at least you're already on your way there in case it is a symptom of something else.
But I get blurred vision when I get migraines, sometimes to the point where I feel like I can hardly see at all. Of course, most of the time I'm not trying to keep my eyes open!
I'm just saying that it isn't always an emergency. Sometimes it's just something that happens.