Referencing of the two-dimensional coordinate system. (a) The geometric centre of the cornea was chosen as the origin. Eight reference lines were created, each passing through the approximate mid-line of a segment of the dissected anterior specimen. (b) Two-dimensional point detection. A combination of the distance (L2) of each data point from its nearest reference line and its distance (L1) along the line from the origin is used as a reference. (c) Each data point is then referenced in the two-dimensional coordinate system.