I think many people will take off their glasses when they are going to do this. It may be a little inconvenient to leave glasses on. As to other people, if they like, they can leave their glasses on during sex. Friend, it is none of our business. But if you don't like this, you can tell your loved ones.
I think if you want to see your loved one clearly. You can wear glasses. But you'd better wear contacts or do this in the day time, because glasses will cause inconvenience when kissing. It will hurt others too. So I suggest you to take off your glasses and replace them with contacts.