Fig. 2. A corneal model system under UV light crosslinking for the epi-on (A) and epi-off (B) case (left figure); and the time-dependent RF concentration profiles versus depth (z) (right figure).at various time t=(0, 135, 270, 540, 810, 1080, 1350) seconds for curves (1,2,3,45,6,7), with an initial UV light intensity I0=10 mW/cm2. The red curves are for C/C0=0,135