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Randomized controlled trial on long-term corneal denervation following small incision lenticule extraction vs laser-assisted in-situ keratomileusis

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First Author: Y.Liu SINGAPORE

Co Author(s):    J. Mehta                    

Abstract Details


To compare long-term corneal nerve status following small incision lenticule extraction (SMILE) versus laser-assisted in-situ keratomileusis (LASIK).


Singapore National Eye Centre


Twenty-four patients were randomized to receive SMILE in one eye and LASIK in the other eye. In-vivo confocal microscopy examination and dry eye assessments were performed at the mean of 4.1 years postoperatively. The patients were further divided into 2 groups based on the mean assessment time: 2.7 years postoperatively for group 1 and 5.5 years for group 2. Another six age-matched normal subjects were recruited.


At 4.1 years, post-LASIK eyes had significantly less corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL), corneal total branch density, and significantly more nerves with beading, than post-SMILE eyes. The CNFD, CNBD, CNFL, and the number of nerves with sprouting were significantly higher in group 2 than in group 1, in both types of surgery, suggesting persistent nerve regeneration. The CNBD and CNFD in group 2, regardless of surgical types, were significantly lower than those in the controls, indicating the nerve status had not recovered to normal ranges even at 5.5 years. High myopic treatment resulted in significantly reduced CNFD in LASIK but not in SMILE. There were no significant differences in the dry eye parameters between 2 procedures at 4.1 years.


The impact on corneal nerves following refractive surgery are long-lasting. SMILE had better nerve preservation and regeneration than LASIK, but neither procedure had recovered nerve status to normal levels even at 5.5 years.

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