By Dr Lee Mun Toong
Corneas normally become thinner after LASIK because the excimer laser that is used removes tissue, especially when higher degrees of spectacle power or larger optical zones are treated. Rarely this thinning causes the cornea to bulge forward and become distorted (ectasia). Like keratoconus, corneal collagen cross-linking has been found to benefit patients with post-LASIK corneal ectasia as well.
Simultaneously cross-linking corneal collagen with LASIK aims to strengthen the cornea at the point of surgery and may be useful in cases where a very thin cornea is expected after the LASIK procedure or having patients with already thin corneas before surgery.
The combination of CXL and LASIK is not indicated in all patients. Based on my experience, It may be indicated in the following cases:
- Patients with completely normal corneas with no signs of keratoconus but with a family history;
- Patients with thin corneas with normal preoperative evaluation (in which risk of ectasia has been ruled out);
- High myopes (requiring large resections)
- Patients who require retreatments, particularly if the thickness of the previous flap is unknown;
- Patients who experienced unexpected thick flap creation during standard LASIK; and
- Patients who experienced unexpected irregular flap creation with variable thickness along its surface.
- Patients with severe ocular allergies, due to the risk of heavy eye rubbing; especially chronic allergic conjunctivitis patient.
It is important to note that cross-linking does not magically restore the vision in any way. It is designed to strengthen the cornea to slow or stop progression and make the cornea more stable.