Yellow corneas and skin are not normal at all. This is a sign of icterus seen with liver and/or gall bladder dysfunction. This cat needs to be examined by a veterinarian immediately. The liver enzymes and liver function test (bile acids) needs to be run. There are other diseases that can cause liver dysfunction--immune mediated diseases are a possibility leading to red blood cell breakdown and icterus. Hopefully your cat is not exhibiting any signs at this point and is still eating. I would not wait to have him examined to figure out the problem--this may be a serious and potentially life threatening disease.
Hi, Cat's yellow cornea might be the symptoms of eye ulcer in cats. It could be early stage symptoms of eye ulcer. It does not bother your cat but still they need on time treatment with proper medicine as in later stage it could harm your cat.
A cat's cornea should not be yellow, I would have the cat checked by a vet to make sure the liver is working properly.