In group B , the speed of sound of the treated corneas was 1746.33 23.37 ms ( -1 ) anteriorly and 1631.60 18.92 ms ( -1 ) posteriorly , while it was 1637.57 22.15 ms ( -1 ) anteriorly and 1612.30 22.23 ms ( -1 ) posteriorly in the controls .