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Similar results obtained with four femtosecond LASIK flap thicknesses
J Refract Surg. 2010;26(6):392-402.
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Four LASIK flap thicknesses created with femtosecond laser yielded similar predictability and visual outcomes, according to a study.
"Thin flaps created by femtosecond laser result in similar visual acuity and refractive predictability results," the study authors said. "The flaps are predictable and planar. The mild variation in the architectural outcomes does not seem to affect the clinical results. Improved femtosecond laser platforms may enhance the structural outcomes further."
The prospective study included 240 eyes randomized to four groups of 60 eyes each to undergo femtosecond laser-assisted LASIK with targeted flap thicknesses of 90 µm, 100 µm, 110 µm and 120 µm. Eyes with predicted residual bed thickness less than 300 µm with a 120-µm flap were excluded from analysis.
Uncorrected visual acuity, best corrected visual acuity and refraction were assessed before and after surgery.
Anterior segment optical coherence tomography was used on 28 points per flap to assess flap thickness at 1 month postop.
Study data showed that mean flap thicknesses achieved were 90.89 µm, 101.3 µm, 110.68 µm and 120.36 µm for the four respective groups.
Preoperative BCVA ranged from 20/16 to 20/40; postoperative UCVA ranged from 20/12.5 to 20/30. No eyes lost lines of BCVA; 25% to 33% of eyes gained one or more lines.
"Postoperative vision and refractive outcome were similar in the four groups," the authors said.
Correction was achieved within 1 D of targeted correction in all eyes. At least 90% of eyes in all four groups had postoperative spherical equivalent refraction within 0.5 D.
Results showed no postoperative flap complications, the authors reported.
First of all, there are already enough data in the literature to support better and safer outcomes with femtosecond laser flaps compared to that of a microkeratome, and this trend is not likely to change. The study shows that the available femtosecond technology is capable of making precise, reproducible and reliable flaps. The procedure is safe and can achieve very similar results even when ultra-thin flaps are desired. The exact thickness that we should pursue is probably around 100 µm to 110 µm. It is known that thinner flaps are more desirable and should be performed in order to preserve the stronger, anterior stromal fibers. However, ultra-thin flaps (90 µm and under) are harder to manipulate and can lead to a higher incidence of interface haze.
– Ronald R. Krueger, MD, MSE
Professor of
Ophthalmology, Medical Director of Refractive Surgery
– Glauco Reggiani Mello, MD
Refractive
Surgery Research Fellow, Cole Eye Institute, Cleveland Clinic
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