A Bowman's Refractive Index (BRI) for quantification of microdistortions in Bowman's Layer (BL) after Small Incision Lenticule Extraction (SMILE) is defined for a patient. BRI is summation of one or more areas of the OCT image of anterior edge of Bowman's layer, quantifies the smoothness of the Bowman's layer. The anterior edge of Bowman's layer is segmented into pixels. After segmentation, a 3rd order polynomial is curve fit to the segmented pixels of the edge of Bowman's layer. BRI is calculated by segmentation of the 3-Dimensional (3-D) OCT image. BRI acts as a marker for mechanical stability and is useful for diagnosis of disease and prognosis of treatments in human.