Efficacy and Safety ofCACXL in the Treatment of Keratoconus With Thin Corneas
Condition: Progressive Keratoconus
MeSH terms: Keratoconus
Study type: Interventional

Summary: 
      The aim of this study is to detect the safety and effectiveness of contact lens assisted
      corneal cross linking in managing progressive keratoconus with thin corneas CACXL was done
      for 40 eyes of 30 of keratoconic patients presented to cornea outpatient clinic in Kasr
      Alainy teaching hospital The UDVA ,BDVA KMAX, thinnest corneal thickness pre-operative and 9
      months postoperatively and the endothelial cell count was measured preoperative and 3 months
      postoperative Demarcation line was measured after 1 month by using ASOCT There was
      statistical significant difference in UDVA and BDVA, there was stabilization of Kmax there
      was decrease in endothelial cell count but not statistically significant According to results
      the procedure seems to be effective and safe un managing progressive keratoconus.
    

Detailed description: 
      Corneal collagen cross linking showed effective results in stabilizing progressive
      keratoconic corneas. It is the only treatment that halts progression of keratoconus, It was
      first described in 1998 by Spoerl et al . A major limitation of the procedure that it cannot
      be used in corneas with pachymetry less than400 micrometers based on the fact that an
      irradiance of 0.37 mW/cm2 has been found to be cytotoxic for the endothelial cell layer.
      Since the absorption coefficient for the human corneas is 70 cm-1 and the intended surface
      irradiance is 3.0 mW/cm2, the 0.37 mW/cm2 irradiance is reached at 300 microns depth. In a
      400 microns thick cornea saturated with riboflavin, the irradiance at the endothelial level
      is 0.18 mW/cm2, which is a factor of 2 smaller than the damage threshold. Therefore, the 400
      microns limit is considered to be a safe limit to protect the endothelium and intraocular
      structures from the hazards of UV irradiation 12 However , the patients with advanced ectasia
      who are desperately in need for cxl , are the same ones who have thin corneas often below the
      threshold which is considered to be safe for CXL treatment However further studies with
      longer follow up and larger numbers of cases are needed to confirm our findings.
    

Intervention name(s): contact lens assisted corneal cross linking
Intervention type(s): Procedure
Intervention description(s): 40 eyes of 30 patients underwent CACXL. The central 9 mm of corneal epithelium was abraded , Iso-tonic riboflavin 0.1% was applied every 2 minutes for 10 minutes on the debrided cornea. A disposable soft Contact lens without an ultraviolet filter (Soflens, Bausch & Lomb) was placed in the inferior fornix during soaking of the stroma with riboflavin for 10 minutes. The contact lens was applied on the corneal surface and the cornea was exposed to ultraviolet-A irradiation at fluence of 3.0 mW/cm2 for 30 minutes The uncorrected (UDVA) and best corrected (BDVA) visual acuity, and maximum (K max) keratometric values, were assessed before, and after 9 months CXL. Endothelial cell count was assessed before and 3 months after CXL. Anterior segment OCT was done 1 month after CXL to evaluate the presence and depth of the corneal stromal demarcation line.
Intervention model: Single Group Assignment
Intervention model description: patients with progressive keratoconus with thin corneas less than 400 micron
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: cross linking; thin corneas; Advanced keratoconus