Collagen Cross-LinkingStudy of the Safety and Effectiveness of Collagen Cross-Linking at an Irradiance of 9 mW/cm2 and 18 mW/cm2

General Inclusion Criteria

Prospective subjects must meet all of the following criteria to be eligible for participation:

• 18 years of age or older
• Signed written informed consent
• Willingness and ability to comply with schedule for follow-up visits
• Contact lens removal prior to evaluation and treatment

Inclusion criteria for progressive keratoconus

Prospective subjects must meet two of the following criteria:

• Having a diagnosis of progressive keratoconus:
• An increase of ≥ 1.00 D in the steepest keratometry value
• An increase of ≥ 1.00 D in astigmatism manifest refraction
• A myopic shift (decrease in the spherical equivalent) of ≥ 0.50 D on subjective manifest refraction
• Presence of central or inferior steepening on the Pentacam map.
• Axial topography consistent with keratoconus
• Steepest keratometry (Kmax) value ≥ 47.00 D

Inclusion criteria for ectasia

Prospective subjects must meet the following criteria:

• History of having undergone a keratorefractive procedure
• Meeting two of the following criteria
• Steepening by topography, either Pentacam or Humphrey
• Thinning of cornea
• Shift in the position of thinnest portion of cornea
• Change in refraction with increasing myopia
• Development of myopic astigmatism
• Development of irregular astigmatism
• Loss of best spectacle corrected acuity. 6.2 Exclusion Criteria

Subjects meeting any of the following criteria will be excluded from this protocol:

• Eyes classified as either normal, atypical normal,
• Corneal pachymetry ≤ 350 microns at the thinnest point measured by Pentacam in the eye to be treated
• A history of chemical injury or delayed epithelial healing in the eye to be treated.
• Pregnancy (including plan to become pregnant) or lactation during the course of the study
• A known sensitivity to study medications
• Patients with nystagmus or any other condition that would prevent a steady gaze during the treatment
• Inability to cooperate with diagnostic tests.
• Patients with a current condition that, in the investigator's opinion, would interfere with or prolong epithelial healing.
• Taking Vitamin C (ascorbic acid) supplements within 1 week of the cross-linking treatment.
• Patients who are unable to remain supine and tolerate a lid speculum for an extended period of time.