The purpose of this study is to evaluate the effectiveness of using riboflavin and UV light to treat progressive keratoconus or post-refractive corneal ectasia.

The primary objective of this study is to evaluate two riboflavin-dosing regimens for corneal collagen cross-linking to slow the progressive changes in corneal curvature in eyes with progressive keratoconus or post-refractive ectasia.

Inclusion Criteria:

1. 10 years of age or older

2. Having documented ectasia on topography or tomography after previous refractive surgery OR progressive keratoconus defined as one or more of the following changes over a period of 36 months or less before randomization:

   1. An increase of ≥ 1.00 D in the steepest keratometry value (or sim K)
   2. An increase of ≥ 1.00 D in regular astigmatism evaluated by subjective manifest refraction
   3. A myopic shift (decrease in the spherical equivalent) of ≥ 0.50 D on subjective manifest refraction
   4. Documented decrease in visual acuity associated with irregular astigmatism and topographic features of ectasia.

3. Subjects with keratoconus diagnosis only:

   a. Axial topography consistent with keratoconus b. Presence of central or inferior steepening on the Pentacam map. c. Presence of one or more slit lamp findings associated with keratoconus, such as: i. Fleischer ring ii. Vogt striae iii. Corneal thinning iv. Corneal scarring

4. Contact Lens Wearers Only: Removal of contact lenses for the required period of time prior to the screening refraction:

   Contact Lens Type Minimum Discontinuation Time Soft 3 Days Soft Extended Wear 1 Week Soft Toric 2 Weeks Rigid gas permeable 2 Weeks

5. Signed written informed consent

Exclusion Criteria:

• 1. Any keratoconus patient over 21 years of age without evidence of progression of his corneal deformity.

  2. Patients with excessively thin corneas. 3. Previous ocular condition in the eyes to be treated that may predispose the eye for future complications, for example:

  a. History of corneal disease (e.g., herpes simplex, herpes zoster keratitis, recurrent erosion syndrome, corneal melt, corneal dystrophy, etc.) b. Clinically significant corneal scarring in the proposed treatment zone 4. A history of chemical injury or delayed epithelial healing in the eye(s) to be treated.

  5. A known sensitivity to treatment medications. 6. Patients with a current condition that, in the treating physician's opinion, would interfere with or prolong epithelial healing.

  7. Pregnancy (including plan to become pregnant) or lactation during the course of the study

6 months

Limitations included the 6-month follow up duration and the reduced reproducibility of measurement techniques in eyes with ectasia as compared with normal eyes.