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Femtosecond SBK proves slightly more effective than LASEK for myopia
Am J Ophthalmol. 2009;148(6):830-836.
Femtosecond laser sub-Bowman's keratomileusis and LASEK safely and effectively corrected myopia, according to a study.
However, femtosecond laser sub-Bowman's keratomileusis (SBK) yielded somewhat better visual and refractive outcomes at 3 months after surgery, the study authors said.
The retrospective case series included 2,108 eyes. A total of 1,072 eyes were treated with femtosecond SBK and 1,036 eyes received LASEK with or without mitomycin C. SBK patients had a mean age of 31.03 years; LASEK patients had a mean age of 30.5 years.
The investigators conducted examinations at 1 day, 1 week, and 1 and 3 months after surgery. Eyes with a significant loss in best corrected visual acuity at 3 months underwent another examination at 6 months.
Surgeons used the Schwind Esiris excimer laser to perform SBK and LASEK. A LASIK nomogram was used in SBK, and a PRK nomogram was used in LASEK.
At 1 day postop, mean uncorrected visual acuity was 0.92 in the SBK eyes and 0.62 in the LASEK eyes. At 1 week, it was 0.98 in SBK eyes and 0.78 in LASEK eyes; at 1 month, 0.96 in SBK eyes and 0.91 in LASEK eyes; and at 3 months, 1.06 in SBK eyes and 1.03 in LASEK eyes. The differences were statistically significant at each interval up to 3 months (P < .01 for all comparisons).
At 3 months, mean BCVA was 1.13 in SBK eyes and 1.10 in LASEK eyes. Twenty eyes in the LASEK group and nine eyes in the SBK group had lost two or more lines of BCVA.
After LASEK, loss of BCVA was attributed to haze in two eyes; no SBK eyes had clinically significant haze.
"More studies with longer follow-up and studies dealing with the biomechanical response of the cornea are needed to further elucidate whether [femtosecond] SBK could be really considered an alternative to [surface ablation]," the authors said.
In a large retrospective and non-randomized study, the authors have compared femtosecond very thin flaps (FBSK) to outcomes at 3 months to the surface ablation LASEK, using MMC when more than 50 µm ablation depth, which it uses to represent surface ablation. No real advantage was demonstrated in visual results aside from the earlier recovery with the sub-Bowman’s treatment. Both demonstrate safety and effectiveness; however, surface ablation is likely safer in the long term.
The choice of LASEK with 1 week of therapeutic contact lens wear is unfortunate as the slight edge that FBSK enjoyed may have been different with epithelial brush PRK. Results with this more popular technique have fared better than the less favored LASEK.
– Noel A. Alpins, MD
OSN Refractive
Surgery Board Member