When you are fitted with your first pair of progressive lenses, you may need a short adaptation period typically lasting a few minutes to a few days. This progressive lens has a typical configuration of distance, intermediate and near zones. This is because blending lens powers in progressive lenses lets you see clearly at all distances, but also causes minor aberrations in the peripheral part of the lenses. If you glance to the far right or left, especially when looking down, you see through these peripheral zones of the lenses and your vision may be blurred slightly. Peripheral aberrations also may cause you to experience a sensation of "swim" when you make quick head movements.