The goal of this clinical trial is to study the effects of an experimental (not Food and Drug Administration (FDA)-approved) treatment called corneal crosslinking (CXL) for conditions in which the cornea becomes progressively thin, steep, and misshapen, causing vision to be blurred.

CXL is performed by putting riboflavin (vitamin B2) drops onto the eye and then exposing it to ultraviolet (UVA) light at about the same intensity as you get outdoors on a bright, sunny day. It is designed to stop the progression of disease by strengthening the cornea. Study participants will be at least 8 years of age or older and have a diagnosis of keratoconus, ectasia after LASIK, ectasia after PRK, pellucid marginal degeneration, progressive ectasia after previous CXL treatment or forme fruste keratoconus.

The main question it aims to answer is:

• Does CXL help prevent or slow the progression of someone's corneal condition and vision loss?

Participants will:

• Attend up to a total of 7 in office visits over the course of 6 months, where several eye and vision tests will be given.

Receive CXL (applying riboflavin (Vitamin B2 eye drops) to the eye, then exposing the eye to ultraviolet (UV-A) light).

• There will be two groups of participants. One group will receive the UVA treatment for 18 minutes and the other group will receive the UVA treatment for 24 minutes.

Inclusion Criteria:

Subjects in whom both the subject and study eye meet all of the following criteria are candidates for the study:

1. Be at least 8 years of age or older, male or female, of any race.
2. Have a diagnosis of keratoconus, ectasia after LASIK, ectasia after PRK, pellucid marginal degeneration, progressive ectasia after previous CXL treatment or forme fruste keratoconus based on topography, tomography, and slit lamp examination.
3. Provide written informed consent and a signed HIPAA form. Pediatric subjects less than 14 years of age must sign an assent, and a parent or legal guardian must sign an informed consent.
4. Be willing and able to follow all instructions and comply with the schedule for follow-up visits.
5. If female and capable of becoming pregnant, must not be lactating or pregnant and must agree to use a medically acceptable form of birth control for at least one week prior to the treatment visit and to continue one month following treatment.

Exclusion Criteria:

Subjects in whom the subject or study eye meets one or more of the following criteria will be excluded from the randomized cohort of the study:

1. Normal corneal topography.

2. A history of previous corneal transplant in the study eye.

3. Minimum corneal thickness < 300 (measured by Pentacam and Ultrasound) at the screening exam.

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

   1. History of or active corneal disease (e.g., herpes simplex, herpes zoster keratitis, etc.)
   2. Clinically significant corneal scarring in the central cornea that, in the investigator's opinion, will not allow the subject to achieve functional vision, even with contact lens correction, after the crosslinking procedure.

5. A known contraindication, sensitivity, or allergy to the test article or its components or to study medications.

6. Nystagmus or any other condition that would prevent a steady gaze during the crosslinking treatment or other diagnostic tests.

7. If female, pregnant, nursing or planning a pregnancy, or having a positive urine pregnancy test prior to the randomization of, or treatment of either eye during the course of the study.

8. Inability to remove soft or scleral contact lenses at least 3 days before initial and follow-up examinations.

9. Inability to remove rigid gas-permeable contact lenses at least 2 weeks before initial and follow-up examinations.

10. Inability to return for required postoperative examinations.

11. Presence or history or any other condition or finding that, in the investigator's opinion, makes the subject unsuitable as a candidate for crosslinking or study participation or may confound the outcome of the study.