An example system for corneal treatment includes an illumination system to generate cross-linking in at least one selected region of a cornea treated with a cross-linking agent by delivering photoactivating light according to one or more photoactivation parameters. The system includes a controller to receive input relating to one or more treatment parameters, which include the one or more photoactivation parameters. The controller is configured to output information for adjusting the one or more treatment parameters by (A) determining from the input, a distribution of cross-links for the at least one selected region of the cornea; (B) determining, from the distribution of cross-links, a shape change for the cornea; and (C) determining, from the shape change for the cornea, a change in vision for the subject. Responsive to the output from the controller, the illumination system is configured to adjust at least one of the one or more photoactivation parameters.