I'm putting this here for anyone who does a search on eye infections for their cats:
Most eye infections occur suddenly, ulcerate quickly, and can lead to blindness eventually. This can happen over as little as two to three days.
Kittens are especially susceptible to this. Especially strays, which tend to have kitty leukimia or kitty "aids".
For those who can't afford an emergency vet visit;
The medication (antibiotic) they give cats with infections is the same as amoxicillin for children. The exact same. It's a pink liquid, but my wife and I have often taken a 500 milligram tablet (adult prescription) and "shaved" a tiny bit off, giving it to the cat. The idea is a 10 to 20 milligram dose. It works great. So...if you've got antibiotic laying around...it's a quick way to fix up your cat in an emergency. I've even gone to the dentist to get a few pills, lied and complained of tooth pain/infection to get it. I'm not telling you what to do, or not do, but if you think in advance, your cat will never need to worry about blindness.
BUT, I won't speak for other antibiotics. We only do this with amoxicillin. We keep a supply around handy just in case (1-2 pills, basically!).
However, there is an eye ointment which you can only get at the vet. MOST vets will allow you to buy it, it's only 10-20 dollars. They won't give you the antibiotic without a visit, but that, they may do. You SHOULD get it, but the cat can get better without it. But the chances are better if you get it.