Researcher in Spain have found that two similar laser eye surgery procedures — thin-flap LASIK and LASEK — both are safe and effective for the correction of myopia, but that femtosecond laser-assisted (“all-laser”) thin-flap LASIK produces slightly better visual and refractive outcomes.
Thin-flap LASIK (also called sub-Bowman keratomileusis or SBK) is similar to LASIK, but involves creating a significantly thinner flap on the eye to preserve more corneal thickness under the flap. In the thin-flap LASIK procedures evaluated in this study, the corneal flap was created with a femtosecond laser.
LASEK (laser subepithelial keratectomy or laser epithelial keratomileusis) is a modification of LASIK wherein a very thin flap consisting only of the outer epithelial tissue of the cornea is lifted from the eye after being loosened from the underlying tissue with an alcohol solution. Other commonly performed variations of LASIK include Epi-LASIK and Presby-LASIK.
In both thin-flap LASIK and LASEK, the corneal flap is less than 100 microns thick. In conventional LASIK, it is not unusual for the flap to be greater than 150 microns thick.
Thin-flap LASIK vs. LASEK: Study design
This study compared the visual and refractive outcomes of 1,072 eyes treated with thin-flap LASIK and 1,036 eyes treated with LASEK.
Prior to surgery, all eyes were nearsighted, with a mean of -3.93 diopters (D) of myopia in the thin-flap LASIK group and -3.87 D in the LASEK group.
Outcomes were measured one day, one week, one month and three months after surgery, and included:
- Uncorrected visual acuity (UCVA)
- Best spectacle-corrected visual acuity (BSCVA)
- Gain or loss of BSCVA after surgery compared to before surgery
Thin-flap LASIK vs. LASEK: Results
Analysis of the study data revealed:
- The day after surgery, mean UCVA was between 20/20 and 20/25 in thin-flap LASIK eyes and slightly worse than 20/30 in LASEK eyes.
- At one month after surgery, mean UCVA was nearly 20/20 in thin-flap LASIK eyes and between 20/20 and 20/25 in LASEK eyes.
- At three months after surgery, mean UCVA was slightly better than 20/20 in both groups.
- At three months after surgery, BSCVA also was better than 20/20 in both groups.
At three months after surgery, three eyes (0.28 percent) in the thin-flap LASIK group and ten eyes (0.96 percent) in the LASEK group gained two or more lines of BSCVA compared to pre-surgical levels.
Also at three months after surgery, 9 eyes (0.84 percent) in the thin-flap LASIK group and 20 eyes (1.93 percent) in the LASEK group lost two or more lines of BSCVA compared to pre-surgical levels.
Losses in best spectacle-corrected visual acuity diminished with time. At six months after surgery, only three eyes (0.28 percent) in the thin-flap LASIK group and two eyes (0.19 percent) in the LASEK group showed a loss of two or more lines of BSCVA.
Conclusions
The researchers concluded that both thin-flap LASIK and LASEK are safe and effective for the correction of low to moderate myopia, but all-laser thin-flap LASIK provides faster visual recovery and slightly better visual and refractive results in the three months following surgery.
SOURCE: Comparison between femtosecond laser-assisted sub-Bowman keratomileusis vs laser subepithelial keratectomy to correct myopia. American Journal of Ophthalmology. Published online September 24, 2009.
Tags: laser, laser eye surgery