This prospective, randomized study is being conducted to evaluate the safety and effectiveness of corneal cross-linking (CXL) in patients with keratoconus or post-refractive ectasia (post-LASIK or PRK) utilizing two techniques: the "standard" Epi-Off technique or an Epi-On technique that utilizes iontophoresis (I-CXL) to deliver the riboflavin to the cornea without need for removal of the corneal epithelium. Patients will be randomized to receive CXL treatment with either the Epi-On or Epi-Off technique.

Inclusion:

1. 10 years of age or older

2. Understand and have signed written IRB-approved informed consent

3. Willingness and ability to comply with schedule for follow-up visits

4. Having a diagnosis of keratoconus or post-refractive corneal ectasia (post-LASIK or PRK)

5. Presence of central or inferior steepening on the Pentacam map

6. Axial topography consistent with keratoconus or post-refractive corneal ectasia (post-LASIK or PRK)

7. Presence of one or more slit lamp findings associated with keratoconus, such as:

   1. Scissoring of the retinoscopic reflex
   2. Fleischer ring
   3. Vogt striae
   4. Corneal thinning
   5. Corneal scarring

8. BSCVA 20/20 or worse (<58 letters on ETDRS chart).

9. Contact lens wearers only: Removal of contact lenses for the required period of time prior to the first refraction:

Contact Lens Type Minimum Discontinuation Time Soft 3 Days Soft Extended Wear 1 Week Soft Toric 2 Weeks Rigid gas permeable 2 Weeks Hybrid lenses (SynergEyes; Rose K; Clear Kone) 2 Weeks Scleral Lenses 2 Weeks

Exclusion Criteria: All subjects meeting any of the following criteria will be excluded from the study:

1. A history of previous corneal surgery in the eye to be treated (including previous CXL treatment)

   a. Eyes with episodes of hydrops or scarring from hydrops may be included as long as there is no active inflammation

2. Corneal pachymetry < 400 microns at the thinnest point measured by Pentacam

3. Previous ocular condition (other than refractive error) in the eye(s) to be treated that may predispose the eye for future complications or prevent the possibility of improved vision, for example:

   1. History of corneal disease (e.g., herpes simplex, herpes zoster keratitis, recurrent erosion syndrome, corneal melt, or corneal dystrophy, etc.)
   2. Clinically significant corneal scarring in the treatment zone

4. A history of chemical injury or delayed epithelial healing in the eye(s) to be treated

5. Pregnancy (including plan to become pregnant) or lactation during the procedure

6. A known sensitivity to study medications

7. Nystagmus or any other condition that would prevent a steady gaze during the cross-linking treatment or other diagnostic tests

8. A condition that, in the investigator's opinion, would interfere with or prolong epithelial healing

9. Presence or history of any other condition or finding that, in the investigator's opinion, makes the patient unsuitable as a candidate for cross-linking or study participation or may confound the outcome of the study

10. Inability to cooperate with diagnostic tests or inability to understand the informed consent.

11. Concurrent use of systemic (including inhaled) medications that may impair healing, including but not limited to: antimetabolites, isotretinoin (Accutane®) within 6 months of treatment, and amiodarone hydrochloride (Cordarone®) within 12 months of treatment.