Influence of Pupil Width

First remove the spherical prescription glass (enter 0.0 for the sphere). If now pupil width is set to 4.0 in the window that opens after clicking to Image Param., the resulting Landolt’s ring shows a large halo. Such halos are reported from pseudophakic patients under mesopic conditions. The halo can be modified by minus-prescription glasses, however, visual impression never becomes satisfying. The variation range of the spherical aberration is so high, that always large areas contribute to the blurred part of the image information. If now pupil width is stepwise decreased in the range of 2.5mm to 0.5mm with a stepwidth of 0.5mm, visual impression first is improved, but then worsenes again below 1.0mm. This is caused by the diffraction at the pupil aperture. The diffraction alone is responsible for a blurring inversely proportional to the pupil diameter. After all, reset pupil width to 2.5 before calculating the next example.