Somebody mentioned blocking both UVA and UVB, which is the right idea.

I read a brief article about SPF 45 blocks about 98% of UVA and UVB, SPF 30 blocks about 96.5% and SPF blocks 95%. But since then I've lost the article, so I don't have the article title or author's name. Maybe a google search, but I'm too lazy.

I avoid getting it in my eyes by not putting it on my forehead, which I figure is covered by a cap and helmut. I also follow the directions by putting it on 20 or so minutes before I go into the sun. I reapply every couple of hours, or when I stop for a rest, or if its looking like I'll be heading into the sun for an extended period of time.