Please tell me more about his eyes.
Are they clear?
Is he able to see?
Does he close the eyelids?
Is the tearing cloudy or clear?
If the tears are clear and the membranes around the eye are not inflamed he probably does not have an infection in the eyes. It could be an allergy or sensitivity.
The best thing to do since he's already dealing with joint ill is to play it safe and treat for both an infection and allergy.
Treat his eyes with an antibiotic/steroid ointment twice each day. You should be able to get the ointment from your veterinarian.
If one or both eyes become cloudy, discontinue the ointment and have your veterinarian examine the eyes.
Sorry. I didn't read what you have Already Tried.
I have opted out so that another veterinarian may be of help.