Inclusion Criteria:  documented progressive keratoconus changes in uncorrected distance visual acuity (UDVA) above 1.00 D Corrected distance visual acuity (BCVA) above 1.00 D spherical equivalent greater than 0.50 D  Exclusion Criteria:  Corneal pachymetry of less than 400 µm less than 2000 cells/cm2, corneal scarring, nystagmus or any motility disorder that prevented a fixed gaze during the examination Current contact lens use