You should close the case absolutely. There are some points you need to note when you use contact lenses. First of all, you might be excited to get your new pair of contact lenses, but you can't take them out from the package and wear them directly. Because the contact lenses are stored in saline solution, which might be irritate to eyes. You should put them in care solution for at least 5 hours before wearing them. You need to wash contact lenses thoroughly with care solution each time before and after wearing them. Rub the lenses tenderly with finger tips to help de-proteinization. After wearing, you should store them in cases with care solution, keeping the case 70% full of care solution. If you happen to stop wearing them, you need to replace the solution each week to ensure the anticepticise function still works. Without solution change in time, a lot of bacteria would stem in the case and contaminate the lenses. Be careful with your hygiene habit of wearing contact lenses to avoid infections.