Colony-forming efficiency (N) expressed as the number of cells giving rise to clones per cornea.

The number of cells giving rise to clones increased from an average of 2275 per cornea for non-cultured cells to 24266 per cornea for cells obtained after culture of limbal explants for 14 days and decreased afterwards (p<0.00001). This figure was close to 0 after 21 days of primary culture. Shown are mean + standard errors of the mean and post-hoc tests.