Effect of corneal collagen crosslinking on femtosecond laser channel creation for intrastromal corneal ring segment implantation in keratoconus

PURPOSE: To evaluate the effect of collagen crosslinking (CXL) on femtosecond laser channel creation for intrastromal corneal ring segments (ICRS) in keratoconic eyes. SETTING: Magrabi Eye Hospital, Cairo, Egypt. DESIGN: Comparative case series. METHODS: Eyes with grade II or III keratoconus were treated by CXL. After 6 months, channel creation was performed using an IntraLase FS-60 femtosecond laser. The eyes were randomly divided into 3 groups. The default femtosecond machine power setting was 1.5 mJ in Group 1, 1.6 mJ in Group 2, and 1.7 mJ in Group 3. A control group included virgin noncrosslinked keratoconic eyes in which the default power setting was 1.5 mJ. The degree of difficulty of ICRS insertion was judged subjectively. The degree of postoperative corneal haze was recorded. RESULTS: Fifteen eyes of 11 patients had CXL. Each group, including the control, comprised 5 eyes. After CXL, intracorneal channel creation using the 1.5 mJ default femtosecond power setting was incomplete and mechanical dissection was required to complete the channel. When the power setting was increased to 1.6 mJ or 1.7 mJ, channel creation could be completed; however, this increased the corneal reaction (haze) postoperatively. The corneal haze resolved in all eyes within 6 weeks, and there were no further complications. CONCLUSIONS: Femtosecond laser channel creation can be performed after CXL; however, the laser power must be modified. Results show channel dissection and ICRS implantation should be performed before or concurrent with CXL.