You're looking at it wrong, like a transaction. But imagine a guy who finds humor and joy while progressively losing eyesight. A guy who's passion for seeing things before they're gone livens and betters all who know him. That guy is somebody people will want to be around. If you sink into bitterness it'll form a self-reinforcing pattern that will ensure your loneliness. And please talk with a professional if you haven't, because that is a heavy thing you're facing and perspective can really be helped by the right person.