Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
While not finding a trigger for Corky's red eye can surely be frustrating, I have to say that I am glad that nothing sinister (ie glaucoma, internal eye infections, etc) have not been found for your lad. And if you have exhausted and ruled out all the primary eye issues for these periods of intermittent redness, then ruling out allergies by using an antihistamine would be worth trying. Specifically, in cases like this, we will use over the counter Piriton (chlorphenamine) at a dose of 2-4mg up to every 8 hours in dogs Corky's size. We tend to start at the lower end of the dose, as this can cause drowsiness (just as in people). And this would be something safe to try to see if you can allay that redness and keep his eye comfortable.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,
I think the piriton is working The eye still gets a little PINK, not red.
He is in good form as usual.
The only other problem he has ever had is anal gland trouble which the Vet sees to every 6/8 weeks. Yuch !