Anyone have a ginger kitty with eye changes?

I'm aware of what it could be but I'm looking for stories where it is a benign thing. We've had him since about 2016, he was left outside by people and abandoned. He's very sensitive to sunlight and tends to burn easily if we don't watch him when he sunbathes. Top left is right after we found him in 2017, top right is 2018, bottom left is 2020, and bottom right is just a few days ago. The only thing different is his eye, no symptoms or masses or anything else. I want to get him into a vet to do tests but I don't have the money right now so I'm just looking for positivity. If he exhibits any symptoms of illness, I won't hesitate to try to get him in somehow. Btw it's only in one eye.