Collagen cross linking in the treatment of corneal ectatic diseases

  • Canan Aslı Utine
  • Hanefi Çakır
  • Muhsin Altunsoy

Turk J Ophthalmol 2009;39(2):153-160

Collagen crosslinking has been widely used in ectatic disease of the cornea. This method causes photopolymerisation of the stromal collagen fibers with the combined effect of the photosensitizing substance riboflavin and ultraviolet A (UVA) beam. After removal of the corneal epithelium ve saturation with riboflavin drops, 3 mW/cm2 UVA (total 5.4J/cm2 surface dosage) is applied for 30 minutes. As a results of a photooxidative mechanism (oxidative desamination), intra-fibrillary covalent bonds increase. After the treatment, new collagen with thicker diameter and resistance to enzymatic degradation is formed. By this way, “freezing” the stromal collagen and increase in corneal biomechanical stability are aimed. Beside keratoconus and iatrogenic keratectasia, this treatment has been tried for reinforcing the effect of intracorneal rings, treatment of corneal melting, bullous keratopathy ve hydrops. Immediately after the treatment, almost complete loss of keratocytes in the anterior and mid-stroma and stromal edema are seen. At the postoperative 3rd month, keratocytes begin to regenerate and edema begin to disappear. The cell density increase progressively in the postoperative period and around 6th month, regeneration of the keratocytes is complete, together with the increase in the stromal fiber density. The mean treatment depth is ~320 µm. After treatment in stroma thicker than 400 µm, endothelial damage is not seen. Together with the topographic decrease in mean keratometry value, approximately 2.5 D decrease in mean spherical equivalent, improvement in morphological symmetry and decrease in corneal aberrations were detected.

Keywords: Ectasia, keratoconus, collagen crosslinking, riboflavin