Astigmatism after contact lens wear.

With-the-rule astigmatism increased by more than 3 D in 2 habitual long-term wearers of contact lenses after they abruptly stopped wearing their lenses. Reducing wearing time gradually over a 2- to 3-month period caused less than 1 D increase in with-the-rule astigmatism in 2 other long-term wearers. All 4 persons had worn polymethylmethacrylate contact lenses for 12 or more years.