Letter to the editor

Department of Ophthalmology, University of Düsseldorf, Düsseldorf, Germany It is with great interest that we read the publication by Kanellopoulos. In this the author shows in a group of 21 patients with 46 months of mean follow-up that the new CXL protocol described, where higher fluence UV light is used with shorter exposure, appears to be a safe, comfortable and effective treatment for stabilizing a progressive keratoconus. This is a very valuable observation. The author also concludes, that collagen cross linking may be a promising adjunct treatment in cases, where a risk of post-LASIK-keratectasia is suspected. LASIK for correction of keratectasia is still controversially discussed. If used as a prophylactic treatment to prevent post-LASIK keratectasia, we would like to point out that the cross linking should be performed preferably after the LASIK procedure because the first will impact various steps of the refractive laser treatment. In 2010 we showed in porcine eyes that CXL reduces the amount of refractive change after a myopic LASIK and results in an increased flap thickness although the laser ablation rate is unaltered. Our study suggests the need for adjustment of microkeratome and laser parameters for LASIK after CXL and indirectly endorses the theory of a immediate stiffening effect of CXL. Meanwhile Kanellopoulos et al also published their results of simultaneous sameday PRK and CXL in which they follow this suggestion. They found that stabilizing the cornea (with CXL) and rehabilitating the vision (with topography-guided PRK) seems to be a promising concept to delay or even avoid corneal transplantation in young adults with progressive keratoconus. Since the indications for refractive laser surgery seem to be progressively expanding, the ophthalmic community needs to reconsider carefully the list of contraindications for ablative surgery weakening the corneal strength and also to be aware that a previous CXL treatment impacts the biomechanical properties of the cornea and microkeratome-assisted refractive surgery. It will remain in the individual surgeon’s responsibility to reassure that a patient seeking LASIK surgery has not been treated with CXL for early keratoconus or other indications previously.