To treat corneal ectatic disorders, systems and methods can precisely apply photoactivating light to specified areas of a cornea treated with a cross-linking agent. An example system includes a light source that provides a photoactivating light to photoactivate a cross-linking agent applied to an eye. The system includes optical element(s) that transmit the photoactivating light to the eye according to a pattern defined by a plurality of treatment zones. The treatment zones are delivered to different respective areas on the eye. The plurality of treatment zones includes at least a first treatment zone and a second treatment zone. The first treatment zone provides a first dose of the photoactivating light. The second treatment zone provides a second dose of the photoactivating light. The first dose is greater than the second dose. The first treatment zone is disposed within an inner boundary of the second treatment zone.
