Does the fish have any cloudiness of any of the other skin, indicating some irritation by parasites? If so, then I would be treating with something like Proform C. I don't particularly like the dip of Tricide Neo, but instead like to mix enough for a quart spray bottle and spray it on the fish. Tricide Neo as a dip causes the fish to shed a lot of slime coat, fouling the water, making multiple dips with it questionable, and once mixed it needs to be kept refrigerated, which makes temperature matching the next day difficult, whereas the spray doesn't have enough mass to need temperature matching, and has not been contaminated by the fish. It is the only treatment that I would use on an eye, so it couldn't hurt. Don't know if it will help or not.
Has the fish run into something in the pond to damage the eye? We always like to see test results as numbers for the tests of ammonia, nitrite, nitrate, pH, and KH, as they tell us a lot about the pond, and it is good water that keeps healthy fish, and there may be something we could use to assist in improving water quality.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard