Givng him 1/2 of his diet in sunflower seeds is harming him mmore than surgery would harm him and probably is the cause of his vitamin A deficiency. If he is like most parrots, sunflower seeds are like candy to him and he will eat them to the exclusion of healthy stuff. A seed diet is notorious for giving parrots a Vitamin A deficiency. A severe Vitamin A deficiency kills.
Instead of sunflower seeds start changing him over to pellets. I don't know what country you live in so don't know what pellets are available. Make sure that there is no sugar in them and that there is added Vits A, E and D3. Cut out the corn as a staple in his diet and give him dark green leafy vegetables like Kale, Romaine lettuce and Swiss Chard. For nuts give him almonds mainly, as those are high in calcium and AGs need more calcium than other birds. Other healthy nuts are walnuts, pine nuts and pistachios. You want him to be healthy and he obviously isn't healthy now.
What is your bird's name and how long have you had him? He really is a beautiful African Grey.