T-Cat Laser & Cross-linking for Keratoconus
Condition: Keratoconus; Pellucid Marginal Degeneration
MeSH terms: Keratoconus
Study type: Interventional

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.
    

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.
    

Intervention name(s): Excimer laser ablation, and collagen cross-linking
Intervention type(s): Procedure
Intervention description(s): 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 intervention name(s): Ricrolin (riboflavin 0.1% in dextran); Pecshke UV-X illumination system
Intervention MeSH terms: Riboflavin; Dextrans
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: keratoconus; pellucid marginal degeneration; corneal ectasia; collagen cross-linking; riboflavin; UV light; excimer laser; Topography-Computer Assisted Treatment (T-Cat); Wavelight Allegretto laser