Washington, DC-Epithelial ingrowth was the primary complication seen in a study comparing LASIK performed with a femtosecond laser (IntraLase, IntraLase Corp.) and a microkeratome (CB, Moria). The incidence of flap complications in the primary LASIK treatments was minimal and identical when performed by the femtosecond laser or microkeratome (0.2%). Epithelial ingrowth, however, had a statistically greater incidence in re-treated eyes when compared with the primary treatments (6.0% versus 0.2%), reported Thomas E. Clinch, MD.
The incidence of epithelial ingrowth was not associated with the method of flap formation or refractive error, continued Dr. Clinch, an associate professor of ophthalmology, Department of Ophthalmology, George Washington University and Washington Hospital Center, Washington, DC.
All LASIK procedures were performed using either a 15-kHz femtosecond laser to create an 8.5-to 9.0-mm diameter flap 100 μm thick or the automated microkeratome with a disposable 130-μm head. A specific platform (Star S4, Advanced Medical Optics) was used to perform all treatments, using wavefront technology (CustomVue) and traditional treatments, pupil tracking, and iris registration when it was available, according to Dr. Clinch.
Most of the refractive procedures in the patients undergoing re-treatments were for myopia.
"To spare stroma, I preferentially treated most of the highly myopic patients with the [femtosecond] laser. This caused the mean spherical equivalent for the [femtosecond-laser] group to be significantly greater when compared with the eyes treated with the [microkeratome]," Dr. Clinch said. He also pointed out that he treated more of the hyperopic patients with the femtosecond laser due to a preference for the predictability of the flap size and configuration.
Regarding the re-treated eyes, 62 of the 64 primary re-treatment procedures were for refractive error; two eyes of one patient required removal of epithelial ingrowth with the femtosecond laser. "This correlated exactly with the [microkeratome]; of the 18 eyes re-treated, 17 were treated for refractive error, and one eye was treated for removal of epithelial ingrowth," Dr. Clinch reported.
About 2% of patients (20 eyes) required a secondary re-treatment. Similar to the previous group, most of these re-treatments were performed to correct residual refractive error; 14 were performed in the femtosecond laser group and one in the microkeratome group. "However, the incidence of re-treatments for epithelial ingrowth was statistically greater in re-treatment procedures (6.0%) when compared with primary LASIK procedures (0.2%)," Dr. Clinch said. "Of those initially treated with [femtosecond laser], five of 991 developed epithelial ingrowth, for an incidence of 0.4% compared with one of 341 eyes treated with the [microkeratome], for an incidence of 0.3%. However, if this is broken down to the percentage of eyes that were re-treated, four of the 64 eyes, or 6.5%, had epithelial ingrowth with the [femtosecond laser] and one out of 18, or 5.5%, had epithelial ingrowth with the [microkeratome]. The incidences were similar," he pointed out.
In an effort to determine who would develop epithelial ingrowth, Dr. Clinch and colleagues analyzed the refractive errors. "We found, however, that there was no correlation with the initial refractive error. One eye had minimal mixed astigmatism, two eyes of one patient had minimal myopia, one eye of one patient had minimal hyperopia, and one eye had minimal myopia," he explained.