Thank you for the additional information and for putting up with all of my questions. I do not think that your kitty needs to see an emergency vet at this point, but I do think that a trip to the vet is a good idea sometime next week. There are several things that could be going on. First, your kitty could be experiencing some discomfort with his eyes, and is rubbing them as a result. It is comforting to hear that the eyeball itself is looking good, but I am concerned that he is squinting occasionally. Older cats are prone to illnesses of the eye just like people are, and some of these are pretty uncomfortable. Your kitty may be experiencing a decreased in tear production which is called dry eye. He may be in the very early stages of glaucoma. He may be experiencing neurological difficulties that are affecting his abilities to control his eye lids, and his eyes are drying as a result. If the eyes become too dry your kitty can develop pin point abrasions to the surface of the cornea, and this can cause quite a bit of discomfort.
Something else to consider is that he is a geriatric kitty now (cats are geriatric at the age of 8), and he may be suffering from a systemic illness that is weakening his immune system, making him more susceptible to secondary infections or prone to illnesses of the eye. The 3 most common ailments known to afflict elderly cats are diabetes, kidney disease and hyperthyroidism. The symptoms include vomiting, diarrhea, increased water consumption, increased urination, dehydration, weakness, weight loss, poor hair coat, muscle wasting, changes in appetite, changes in behavior and increased vocalizations. Diabetics are particularly prone to glaucoma and eye issues.
Step one will be an exam by your vet. From there additional diagnostics will be suggested. Your vet may want to test the tear production and stain the corneas to look for abrasions. Blood and urine tests will rule out systemic illness. Hopefully it will not be anything too serious. Please let me know if I can be of further assistance. If this has been helpful, please hit the green accept button. Good luck, keep me posted!