You could rinse it with saline. If you have a first aid kit there is often a saline eye wash in it. If not you can make some. A teaspoon of salt dissolved in boiling water (ie put a teaspoon of salt in a jug and add boiling water up to a pint level). Then let it go cold. When it's cold iuse a cotton bud dipped in it and gently bathe her eye. Don't have the cotton bud sopping wet or you'll soak the hamster - just slightly wet but not dripping. You could swaddle your hamster in a towel while you do it. Just gently dab the eye area with the saline. It will help soothe as well as heal.
It is more likely your hamster has just half closed the eye because the cream in it - I don't think there's anything in the gel that would make her go blind although gentle eye clean with saline will help remove some of it. Isaderm seems to be mostly a steroid gel with a bit of antibiotic in so I don't think it'll do any real harm but might cause discomfort.
Edit: Posted at the same time as Souffle
If you don't have a cotton bud, use the corner of a soft cloth