T-Cat Laser & Cross-linking for Keratoconus

Sponsor

Moorfields Eye Hospital NHS Foundation Trust (Other)

Overall Status

Completed

CT.gov ID

NCT00777322

Collaborator

Accuvision Laser Eye Clinics (Other), Carleton Optical Equipment Ltd. (Industry), Bon Optics (Other), Sooft Italia (Industry)

Enrollment

Location

Arm

Duration (Months)

0.6

Patients Per Site Per Month

Study Details

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	Phase
Keratoconus Pellucid Marginal Degeneration	Procedure: Excimer laser ablation, and collagen cross-linking	N/A

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.

Purpose:

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.

Design:

Prospective, interventional trial.

Study Design

Study Type:

Interventional

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 :

Oct 1, 2008

Actual Primary Completion Date :

Oct 1, 2010

Actual Study Completion Date :

Oct 1, 2010

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

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

The difference in the pre- and post-operative unaided visual acuity, best corrected visual acuity, and refraction. [At six months]

Secondary Outcome Measures

Corneal topographic profile. [At six months]

Eligibility Criteria

Criteria

Ages Eligible for Study:

18 Years to 50 Years

Sexes Eligible for Study:

All

Accepts Healthy Volunteers:

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.