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T-Cat Laser & Cross-linking for Keratoconus (T-Cat)

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details.
ClinicalTrials.gov Identifier: NCT00777322
Recruitment Status : Completed
First Posted : October 22, 2008
Last Update Posted : July 21, 2011
Information provided by:

Study Description
Brief Summary:
The purpose of this study is to determine whether excimer laser corneal surface ablation (T−Cat) can be safely combined with simultaneous corneal collagen cross−linking treatment to produce an improved and stable corneal profile in the treatment of keratoconus.

Condition or disease Intervention/treatment
Keratoconus Pellucid Marginal Degeneration Procedure: Excimer laser ablation, and collagen cross-linking

Detailed Description:

Theoretical framework:

Corneal ectasia is a relative weakness in the structure of the cornea, which produces a progressive change in its shape with resultant visual distortion.

Excimer laser surface ablation can be used to re−shape the corneal profile. When the corneal shape is very irregular, corneal topography data gives the best information as to how to re−shape the cornea into a normal profile, and this Topography−Computer Assisted Treatment (T−Cat) will be used to modulate the surface corneal shape.

It is known that collagen cross−linking in the cornea occurs naturally with age, and in diabetes, both of which seem to prevent progressive ectasia. Corneal collagen cross−linking with riboflavin has been shown to stabilize the cornea in keratoconus, and prevents progression of the disease. If cross−linking is performed at that moment that the cornea has been re−shaped by T−Cat treatment, it should help prevent the corneal thinning resultant from the laser treatment from destabilising the cornea and causing progressive ectasia.


To determine whether excimer laser corneal surface ablation (T−Cat) can be safely combined with simultaneous corneal collagen cross−linking treatment to produce an improved and stable corneal profile.


Prospective, interventional trial.

Study Design

Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 15 participants
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)
Primary Purpose: Treatment
Official Title: Pilot Study of Excimer Laser Topography-Computer Assisted Treatment (T-Cat) Combined With Corneal Collagen Cross-linking With Riboflavin and UV Light
Study Start Date : October 2008
Primary Completion Date : October 2010
Study Completion Date : October 2010

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Eye Care
Drug Information available for: Riboflavin
U.S. FDA Resources

Arms and Interventions

Arm Intervention/treatment
Experimental: Interventional study
Patients with known keratoconus or pellucid marginal degeneration will be invited to join the study. The study is partly a continuation in the management of patients who have had previous keratophakia, who will have near−normal or supra−physiological levels of corneal thickness. It is also intended for patients with relatively mild keratoconus who have sufficient corneal thickness to allow a limited laser ablation whilst still leaving a residual stromal bed of at least 350μ.
Procedure: Excimer laser ablation, and collagen cross-linking
Surgery is performed with topical anaesthesia. The central corneal epithelium is removed. Excimer laser ablation is applied (typically 15−30 seconds). Residual bed thickness is checked with an ultrasonic pachymeter. Topical application of riboflavin 0.1% in dextran is commenced at 5 minute intervals. When an adequate saturation of the anterior chamber with riboflavin has been achieved, cross−linking treatment will proceed. Output from the UV light generating equipment is measured with a UV light meter and set at 3mW/cm². Thirty minutes of treatment is given, interrupted at five minute intervals by the application of more topical riboflavin drops. Finally the eye has a bandage soft contact lens placed, with preservative free topical antibiotic, steroid, and cycloplegic drop application.
Other Names:
  • Ricrolin (riboflavin 0.1% in dextran)
  • Pecshke UV-X illumination system

Outcome Measures

Primary Outcome Measures :
  1. The difference in the pre− and post−operative unaided visual acuity, best corrected visual acuity, and refraction. [ Time Frame: At six months ]

Secondary Outcome Measures :
  1. Corneal topographic profile. [ Time Frame: At six months ]

Eligibility Criteria

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 50 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Patients with known keratoconus or pellucid marginal degeneration.

Exclusion Criteria:

  • Age < 18 years > 50 years.
  • Minimal corneal pachymetry in eye to be treated of < 400μ.
  • Evidence of other corneal disease in the eye to be treated (e.g. Herpes simplex keratitis).
  • Women who are pregnant or nursing at the time of the initial treatment.
  • Presence of significant central corneal opacity.
  • Patients unwilling to not wear rigid contact lenses in the eye to be operated on for at least one month before baseline examination, and for the first six months post−operatively.
Contacts and Locations

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00777322

United Kingdom
Moorfields Eye Department at St George's Hospital
London, United Kingdom, SW17 0QT
Sponsors and Collaborators
Moorfields Eye Hospital NHS Foundation Trust
Accuvision Laser Eye Clinics
Carleton Optical Equipment Ltd.
Bon Optics
Sooft Italia
Principal Investigator: Chad K Rostron, MB BS Moorfields Eye Hospital NHS Foundation Trust
More Information

Additional Information:
Responsible Party: Mr Chad K Rostron, Moorfields Eye Hospital
ClinicalTrials.gov Identifier: NCT00777322     History of Changes
Other Study ID Numbers: REC Ref: 07/H0721/94
First Posted: October 22, 2008    Key Record Dates
Last Update Posted: July 21, 2011
Last Verified: April 2009

Keywords provided by Moorfields Eye Hospital NHS Foundation Trust:
pellucid marginal degeneration
corneal ectasia
collagen cross-linking
UV light
excimer laser
Topography-Computer Assisted Treatment (T-Cat)
Wavelight Allegretto laser

Additional relevant MeSH terms:
Corneal Diseases
Eye Diseases
Vitamin B Complex
Growth Substances
Physiological Effects of Drugs
Photosensitizing Agents
Dermatologic Agents
Plasma Substitutes
Blood Substitutes