Femtosecond laser channel creation may be less effective after corneal collagen cross-linking

J Cataract Refract Surg. 2011;37:701-705.

Femtosecond laser channel creation for intrastromal corneal ring segment implantation should be performed before or at the time of corneal collagen cross-linking, according to a study.

"Although femtosecond laser channel creation can be performed safely after [corneal collagen cross-linking], it is better to perform channel dissection before or concurrent with [corneal collagen cross-linking]," the study authors wrote. "This results in less energy use, better dissection and less corneal haze."

The comparative case series included 15 eyes that underwent cross-linking and five control eyes. All had grade 2 or grade 3 keratoconus.

Intracorneal channel creation using the IntraLase FS-60 femtosecond laser (Abbott Medical Optics) was performed 6 months after cross-linking. Three groups, each comprising five eyes, underwent channel creation using varying degrees of laser power.

The power setting was 1.5 mJ in group 1 as well as for the five control eyes, 1.6 mJ in group 2, and 1.7 mJ in group 3.

In group 1, mechanical dissection had to be performed due to incomplete channel creation. Groups 2 and 3 achieved channel creation, but corneal haze increased, resolving by 6 weeks postop. Overall, the efficacy of channel creation was lower in eyes that had undergone previous corneal collagen cross-linking.

The study authors suggested that cross-linking may affect the deeper stroma and that a cross-linked cornea may also be less clear, decreasing the effectiveness of laser penetration.