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.

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.

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.