A few months ago, I noticed my cat, Sadie, had gotten quite thin. It seemed to happen overnight although I know it was a more gradual process that I didn't notice until she seemed shockingly thin. I took her to the vet who drew labs and told me the possible diagnoses (cancer, diabetes, thyroid ).
As I waited for the labs, I beat myself up for not noticing her weight loss sooner and jumped to the worst possible conclusions. Thankfully, it is the most manageable diagnosis - thyroid - and she is now on medication and doing well. As you mentioned with your cat's eye, it was a scary reminder that I need to be more proactive with regular check-ups and preventative care.
I'm glad you received good news about your kitty's eye!!