Eye damage from sun in viewfinder accidentally?

Hi all

I was on a train yesterday going through the mountains in Switzerland and while I was waiting for the right moment to take a photo I saw the sun come into view in the viewfinder (the train turned a corner). My natural reaction seemed to be to look at the sun and then move my eye away from the camera as soon as I could (perhaps after 0.75 seconds). Should I be worried about eye damage?

This was just before 5pm but the sun was still quite high in the sky. My 18-55mm lens on a Nikon D40 was set to 24mm and I had no filters on the lens. The sun didn't seem too bright in the viewfinder and I noticed no after effects at the time or in the 29 hours since. The train window was closed and I was wearing prescription (clear) glasses (supposedly with 99% UV protection).

I would appreciate any opinions. I normally try to avoid the sun at all costs so I am annoyed that this happened. I understand that brief glances at the sun with the naked eye should be OK although not something to make a habit of, but I was wondering about the fact that the viewfinder of a camera would concentrate the sun's rays onto a small area.

Thanks in advance!