These lenses correct myopia. They do not correct astigmatism. They are available in the prescriptions: 0, -2, -3, -4, -5 et -6. Each lens is independent in order to adapt to each eye. The optical correction may not be perfectly adapted to your sight. This is not a problem and is not dangerous when exercising for 2 hours, provided that it is as close to your correction as possible. In case of doubt, seek your optician's advice.