Evaluating the Safety and Efficacy of the KXL System for Corneal Collagen Cross-Linking in Eyes Having Keratoconus

Inclusion Criteria: 1. Age Limit for for keratoconus and Plec:18 years 2. Sign the informed consent. 3. Willingness and ability to follow all instructions and comply with schedule for follow-up visits; 4. Contact Lens Wearers Only: Minimum of 3 days 5. For KC subjects: 1. Axial topography consistent with keratoconus(Pentacam ) 2. Presence of central or inferior steepening on the Pentacam map; 3. Steepest keratometry (Kmax) value ≥ 47.00 D; 4. May have corneal scarring up to and including CLEK grade 4.0 (any scarring up to a dense/opaque stromal scar consistent with KC) 5. Keratoconus progressing over time ( evidenced by topography changes, visual acuity or refractive changes) 6. For PLEc subjects: 1. Having a diagnosis of corneal ectasia after corneal refractive surgery (e.g., LASIK, PRK, epi-LASIK,LASEK,) 2. Presence of central or inferior steepening on the Pentacam map. 3. Axial topography consistent with corneal ectasia Exclusion Criteria: 1. Contraindications, sensitivity or known allergy to the use of the test article(s) or their components; 2. If female, be pregnant, nursing or planning a pregnancy or have a positive urine pregnancy test at Visit 2 prior to randomization or during the course of the study; 3. For KC and PLEc subjects, corneal pachymetry that is \< 400microns prior to epithelial debridement at the thinnest point measured by Pentacam in the eye to be treated; 4. A history of chemical injury or delayed epithelial healing in the eye(s) to be treated; 5. Patients with nystagmus or any other condition that would prevent a steady gaze during the treatment or other diagnostic tests; 6. Patients with a current condition that, in the investigator's opinion, would interfere with or prolong epithelial healing; 7. Taking Vitamin C (ascorbic acid) supplements within 1 week of the cross-linking treatment,retinoic acid within 6 months of treatment 8. Previous ocular condition (other than refractive error) in the eye to be treated that may predispose the eye for future complications. For example: 8.1. History of corneal disease (e.g., herpes simplex, herpes zoster keratitis, recurrent erosion syndrome, corneal melt, corneal dystrophy, etc.); 8.2. Clinically significant corneal scarring in the cross-linking treatment zone or in the investigator's opinion, will interfere with the cross-linking procedure; 9. For KC subjects 9.1. Eyes which are aphakic; 9.2. Eyes that have the maximum corneal curvature (Kmax), as identified and measured by Pentacam, outside of the central 5mm zone; Note: In addition, the Investigator may exclude or discontinue any subject for any sound medical reason.