Figure 7. The elastic modulus of corneas having received CXL and PTK on the same day (Group 1A), PTK 35 days before CXL (Group 2A), and PTK only (Groups 1B and 2B). Group 1A corneas had a significantly higher elastic modulus than Group 1B corneas at day 21, but the elastic modulus was similar by day 90. However, no significant differences were observed between Group 2A and Group 2B at either time point. * p <0.05, two-way ANOVA followed by Tukey’s multiple comparisons test).