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J.C. Erie, S.V. Patel, J.W. McLaren, W.M. Bourne; Corneal Nerve Morphology and Function After Bladeless and Microkeratome LASIK. A Randomized–Controlled Study . Invest. Ophthalmol. Vis. Sci. 2006;47(13):516.
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© ARVO (1962-2015); The Authors (2016-present)
To compare changes in subbasal nerve density and corneal sensitivity in eyes randomized to LASIK performed with a microkeratome or LASIK performed with a femtosecond laser (bladeless).
Twenty patients received LASIK for myopia or myopic astigmatism. One eye of each patient was randomized to flap creation by using a microkeratome (Hansatome, Bausch & Lomb, Rochester, NY) with intended flap thickness of 180 µm, and the fellow eye to flap creation with a femtosecond laser (IntraLase FS, IntraLase Corp., Irvine, CA) with intended flap thickness of 120 µm. Corneas were examined by using confocal microscopy in vivo before and at 1, 3, and 6 months after surgery. Subbasal nerves were measured and nerve density was calculated as the total visible length of nerves per area (µm/mm2). Corneal sensitivity was determined at each visit by using a Belmonte esthesiometer that measured the threshold to mechanical stimulation by a 2–second puff of air (ml/min). Differences between pre– and post–operative nerve densities and corneal sensitivities were compared by using signed–rank tests.
Nerve density did not differ between treatments at any time (Table), but was decreased at 1, 3, and 6 months after both treatments (P<0.001) compared to before LASIK. Corneal sensitivity also did not differ between treatments at any time (Table). The mean sensitivity threshold was elevated a nonsignificant 30–31% at 1 month after both treatments compared to preoperative (P>0.14, minimum detectable differences = 29 [microkeratome] and 55 [bladeless], α =0.05, ß=0.20).
Subbasal nerve density is significantly reduced for up to 6 months after LASIK whether the flap is created by using a microkeratome or a femtosecond laser. The anatomical loss of subbasal nerves does not correspond to changes in mechanical corneal sensitivity.
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