How do you treat yellow plaque around the eyes on birds?

I have a 12-year-old pigeon who had a granular yellow plague around his right eye. The small feathers around the eye stuck to it as they grew in, resulting in quite a mess for the bird that completely covered his eye. I tried several times to remove it but it pulled on the skin around the eye, so I backed off. It was really stuck. But after over a year I decided to tackle it again with warm water, a clean cloth, a comfortable chair (the most important part so I could work on him for a long time), and dabbed at his eye gently until the growth started coming off bit by tiny bit. His eye is sore from me rubbing and pulling on it, but underneath that mess and after all this time, his eye seems fine. I may put prophylactic Amox in his water for 2 days and watch him closely for infection and signs of the plaque returning.