At 12 months postoperatively , a reduction of the refractive astigmatism from 1.930.90 D ( range : 0.50 to 4.00 D ) to 0.280.61 D ( range : 0.00 to 1.50 D ) could be found , with patients achieving a mean UDVA of 0.060.16 logMAR ( range : -0.18 to 0.40 logMAR ; Snellen 20/20 ) .