I really have trouble driving in the rain. I have strabismus esotropia, which basically means that my eyes didn't line up when I was born - one of them turned in. Actually, I think they both turned in to some degree. If I understand correctly, its because the muscles on the inside of the eyeball are too short, so they pull the eye inwards. I've had surgery on both of my eyes to straighten them out (once when I was 3, once when I was 19), but those were just cosmetic and didn't help my vision at all. The big problem is that I don't really have depth perception. When you're a baby and learning how to see, if your eyes don't line up well enough your brain can't put the two images together (which is what gives you depth). So it just ignores one eye - I always see out of only one eye at a time. It alternates which one though, because one of my eyes is nearsighted, thats the one I read with. The other eye is good for both distance and vision. I wear glasses when I drive because my nearsighted eye likes to try to do more of the work, which is a problem, and I get really tired when I have to concentrate on using the better eye. Mostly my eyes look straight now, which is good, except when I'm tired or really angry. In fact, Brian finds this to be a handy barometer for knowing the degree to which he is in trouble. Ha.
Anyhow, not having depth perception makes it tougher for me to drive in the rain and in the dark. In the dark I have fewer visual cues to help me determine how far away something is. In the rain, I also have that problem as well as having trouble focusing past everything going on on the windshield. Maybe thats not really a depth problem though. (Also, having no depth perception means that I don't have a career as a tennis, volleyball, basketball or baseball star - I can't judge how high up the basketball net is, I consistently swing when the ball is not quite to me yet, and I could never tell whether it was even on my side of the net or not.)
I know that technically Rain-X has always been meant for car windshields. But I'm a dorky lab type, so I have only ever used it to coat one of the glass plates in a sequencing or protein gel so that you can get them apart more easily when you're done. My fancy hybrid has trouble clearing rain off of the back window though. I don't know if the angle of the window is funny or what, but when its raining I can hardly see out of the back. So I bought some Rain-X and had Brian put it on for me. He also put it on my front windshield, which I hadn't meant for him to do, but oh well.
Yesterday was the first day I drove in the rain with the Rain-X and it was a miracle. I'm so disappointed that I didn't figure this out until I was 31 years old. The rain just slid right off my windshield. I could have even driven without my wipers off (not that I would have). In fact, my friend said that the wipers on her old boyfriend's car were broken, so he used Rain-X.