First of all, you need to make sure that it IS a retained eyecap and not just a wrinkled eyecap. I have a female that I was totally convinced had a retained eyecap. Then she shed and I noticed that when I examined the shed she had shed both eyecaps, even though one still looks wrinkled to this day.
Leave the snake alone and wait for the next shed. Check the shed and see what you've got going on. MEssing with it when you're not sure CAN blind your snake, and I know that is exactly what you're trying to avoid.
At that point, after the shed if there is still a problem I'd say take it to a vet... you've been doing the right thing with the soaking so if it is retained after next shed then it is a stubborn one and might take some professional help.
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All my Children: 0.2 female humans (1 is 10 and the other is a 6 month old hatchling), 1 Saint Bernard, 2 maine coons, 15 leopard geckos, 1 pacman frog, 1 oscar, 1 jack dempsey, 1.1 ball pythons, and "Lilith" the black meowing kitty