I think you can, and also you should wear the glasses while playing tennis, especially if you are nearsighted; because I think you can not see where the ball is without the vision help. I know you are afraid that your eyeglasses will knock off, in fact I understand you because my eyeglasses have knocked off while playing tennis (the situation embarrassed me). If you are the first time to wear the glasses, and you are new to it, you can buy a glasses strap to prevent falling. Of course, if you have been with glasses for some time, I think there is no problem for you, and you can just enjoy your time. Nevertheless, what maybe annoy you is that the sweat, if so, you can wear the contact lenses.