If they catch birds and mice- it is necessary. That's primarily where they get worms. and I've heard over and over that ALL kittens are born with worms- all kittens are automatically given Strongid. I had 3 kittens that I trapped behind a Caldor's that had great stools (albeit hard and black from eating bugs and sticks, etc) but had dry coughs. Turned out they had lung worm- very rare and the vet told me they don't really know much about lung worm re: how they get it but is likely from eating raw meat (birds from mom cat). They were treated successfully.
Eye worm intrigues me- it's apperently on the west coast and I haven't seen it or heard about it here on the east coast, thank goodness! Once, a friend of mine's rescued foster cat who she treated for tape worm, threw up the tape worm and she discovered it while we were on the phone chatting. She started yelling, "Oh Yuck! Gross! Ick! Gross!"etc. She said the tape worm was so large that the mouth was clearly visible- they hang on to the intestines with their mouths, so once dead, up they come!