Contact lens assisted corneal cross linking in thin ectatic corneas - A review

Contact lens-assisted corneal cross-linking (CACXL) was introduced by Jacob et al. in 2012 for treating thin keratoconic corneas using riboflavin soaked soft contact lens to artificially increase the functional corneal thickness. It is advantageous over other thin corneal cross-linking techniques as it works independent of swelling properties of the cornea, is an epi-off technique and does not require additional time, additional expensive equipments or special solutions. The only additional requirement as compared to all other techniques is a UV barrier-free soft contact lens (Soflens^TM, B&L) which is easily available and inexpensive. Advantages include simplicity, easy adaptability, early visual rehabilitation, good visual outcomes, safety, and efficacy. Progression rates are acceptable and the need for re-treatment has been low. CACXL can help regularize corneal shape and may be used in isolation or synergistically with Intracorneal ring segments (ICRS) or Corneal allogenic intrastromal ring segments (CAIRS). It gives about 70% stiffening as compared to standard Dresden protocol CXL in less ideal porcine eye studies. Murine eye models that closely mimic thin corneas and show greater cross-linking effect as compared to porcine eyes may be a better model for evaluation of CACXL, however further studies are needed. Care should be taken in selecting the right kind of contact lens. Proper technique should be followed, especially by confirming thinnest functional pachymetry to be above 400 microns intra-operatively before application of UV-A. The sub-contact lens riboflavin film should be avoided as also an excessively thick supra-contact lens riboflavin film and too many re-applications.