Virtually everybody has some degree of astigmatism that can reduce their vision without glasses or contact lens.
Astigmatism in its simplest form is where the cornea or front of the eye is not perfectly round, like a football. With astigmatism the cornea is perhaps shaped a little more like a rugby ball and this can degrade your vision.
At surgery we will try to reduce the amount of astigmatism, by performing relaxing incisions in the cornea to reshape it. Unfortunately it is sometimes not possible to reshape the cornea sufficiently and therefore you may still have some residual astigmatism post operatively which may prevent best uncorrected vision, which means you may still require glasses, either for reading and distance.