My cat had the same problem about a couple of weeks ago .He had mucus(or yellow looking liquid) in both eyes i took him to the vet and he gave me Terracing Ophthalmic ointment for 10 days 3 times a day along with Panmycin Aquadrops twice daily and it cleared up the infection.

 The only advice I could give you is to go back to the vet and tell him/her the situation you're having with your cat. Explain to the vet the same thing you asked here. No one can prescribe something for your pet better than a vet! I know it costs a lot of money but it is better to go there before your cat can get a really bad eye infection and hence lose an eye. I'm sure you wouldn't want that to happen. Good Luck!