I remember watching food network when I was younger and there was a tip that I once tried. Cut an onion next to a stove top flame.
I don't remember exactly but when you cut an onion, the juices from the onion fly up into the air and get in your eyes causing them to water. When cutting next to a flame, the heat coming from the flame causes to reduce the spray from the onion? something along those lines.
Now a days along with everyone else, my eyes don't really water while cutting an onion. Only from time to time. But when I was younger, cutting near an open flame really worked!