Hello, my name isXXXXX and I have over 20 years of experience as a veterinarian.
I'm sorry to hear about Sammy's eyes and I am very concerned for him.
What you have described is a condition called uveitis, which is inflammation of the eye including the iris, blood vessels that supply nutrition to the eye and the muscles that control pupil size.
Symptoms of uveitis include squinting, sensitivity to light, raised third eyelids, tearing, redness to the white part of the eye, abnormal pupil shape or size, and a change in iris color. Some cats will also have cataract formation or cloudiness to the eye and if glaucoma develops secondarily a larger then normal, protruding eye.
There can be many reasons for uveitis but in the majority of cases (60%) we never find the cause. In cases where a cause can be identified though it is usually due to serious diseases including infectious diseases like feline leukemia, feline immunodeficiency virus, feline infectious peritonitis, toxoplasmosis, bartonella or Herpes virus, trauma or cancer including melanoma or lymphoma.
If a cat has uveitis for long enough and it is not successfully controlled it can progress to glaucoma, or increased intraocular pressure. That is what I am concerned about now with your fellow.
I would recommend starting by testing Sammy for feline leukemia, feline immunodeficiency virus (which have been done) and toxoplasmosis.
I also recommend checking his intraocular eye pressures and getting him examined by a veterinary ophthalmologist. If you'd like to find one in your area here is a link:
A veterinary ophthalmologist will be able to look inside his eyes to look for a tumor, check for glaucoma and examine his eyes much more closely because they have specialized equipment to do so.
In the meantime to control inflammation I would add an oral anti-inflammatory to the topicals he is already being given.
I cannot recommend more directed therapy without knowing why your fellow's eyes are the way that they are.
Best of luck with Sammy.