annie is right....using the wrong or an OTC worm medication can be very harmful.
also wanted to ask is he moving his bowels okay????
CR, I think she is saying that since the kitty is old enough for the eyes to be their adult color, it is not younger than 8 weeks.
I agree, it is probably worms. Don't use an over-the-counter worm prep if you can avoid it, they are harsh and might not hit the right kind of worms. (Years ago I wormed my cat twice with roundworm meds when he had tapeworms. What a stupid move.) Anyway, see the vet and take in a stool sample, it is likely that worms are the problem but you don't want to guess wrong.
Dear Emmaloo, your new kitten might have worms if its belly is swollen. What is your question about the eyes? Glad to help. Pamela