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S. V. Patel, J. W. McLaren, W. M. Bourne; Keratocyte Density Three Years After LASIK: Bladeless versus Microkeratome. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4524.
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We previously found that keratocyte density decreased in the stromal portion of the flap after LASIK with the flap cut by a mechanical microkeratome. In this new paired-eye study, we compared keratocyte density after LASIK with the flap cut by a femtosecond laser (bladeless) to LASIK with the flap cut by a microkeratome.
Fifteen patients received LASIK for myopia or myopic astigmatism. One eye of each patient was randomized by ocular dominance to flap creation with a femtosecond laser (IntraLase FS, IntraLase Corp., Irvine, CA), and the other eye to flap creation with a microkeratome (Hansatome, Bausch & Lomb, Rochester, NY). Corneas were examined by using confocal microscopy before surgery and at 3 years after surgery. Central keratocyte density was measured in the anterior and posterior halves of the stroma in the flap by using a custom program that objectively identified bright objects (presumed to be keratocyte nuclei) in confocal images. Cell density was compared between treatments by using paired t-tests (unless stated), and the minimum detectable difference (MDD) was calculated for non-significant differences (=0.05, ß=0.20).
In the anterior half of the stromal flap, keratocyte density before bladeless LASIK (43,071 ± 7421 cells/mm3, mean ± standard deviation) did not differ from keratocyte density before LASIK with the microkeratome (39,228 ± 5371 cells/mm3; p=0.13, MDD= 7200 cells/mm3). At 3 years, keratocyte density in the anterior stromal flap also did not differ between treatments (bladeless, 34,740 ± 7359 cells/mm3; microkeratome, 35,693 ± 6040 cells/mm3; p=0.72, MDD= 7800 cells/mm3). In the posterior half of the stromal flap, keratocyte density before bladeless LASIK (27,269 ± 5081 cells/mm3, mean ± standard deviation) did not differ from keratocyte density before LASIK with the microkeratome (27,269 ± 4591 cells/mm3; p=0.99, MDD= 5350 cells/mm3). At 3 years, keratocyte density in the posterior stromal flap also did not differ between treatments (bladeless, 21,340 ± 4592 cells/mm3; microkeratome, 20,813 ± 4631 cells/mm3; p=0.71, MDD= 4200 cells/mm3). Keratocyte density at 3 years was 19% and 22% lower compared to preoperative in the anterior (p=0.005) and posterior (p<0.001) flap, respectively, after bladeless LASIK, and 9% and 24% lower in the anterior (p=0.01, signed-rank test) and posterior (p<0.001) flap, respectively, after LASIK with the microkeratome.
Keratocyte density decreases in the flap after LASIK, regardless of how the flap was created. Cutting the flap with the femtosecond laser is not associated with increased keratocyte loss compared to loss after using the microkeratome.
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