To compare the influence of femtosecond lenticule extraction (FLEx) and small incision lenticule extraction (SMILE) on corneal nerve density and the ocular surface for equivalent degrees of correction of myopia.
Sixty eyes of 30 patients (8 males and 22 females, mean age: 31.0 ± 6.0 years) were included in the study. The patients underwent FLEx in 1 eye and SMILE in the other eye by random assignment. Subbasal nerve density was measured using confocal microscopy preoperatively and at 1 week, 1 and 3 months, and 1 year postoperatively. Ocular surface parameters such as Schirmer’s test results, tear film break-up time, and corneal sensation were performed preoperatively and at 1 and 3 months postoperatively.
In the FLEx group, subbasal nerve density was 18,390 ± 6,090 µm/mm2 preoperatively and 5,770 ± 3,490 µm/mm2 at 1 year postoperatively (P < .001, Dunnett’s test). In the SMILE group, subbasal nerve density was 16,810 ± 6,220 µm/mm2 preoperatively and 11,870 ± 8,200 µm/mm2 at 1 year postoperatively (P = .21). The decrease in corneal nerve density was significantly less after SMILE than after FLEx at all postoperative visits (Mann–Whitney U test, P < .05). FLEx resulted in a significant decrease in Schirmer’s test results, tear film break-up time, and corneal sensation at all postoperative visits, whereas SMILE induced no significant changes in these parameters (P > .05).
There was less damage to the sub-basal nerve plexus of the cornea and less effect on the ocular surface parameters after SMILE than after FLEx.
[J Refract Surg. 2015;31(1):10–15.]
From the Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan.
The authors have no financial or proprietary interest in the materials presented herein.
Study concept and design (KK, KS); data collection (AI, RI, HK); analysis and interpretation of data (RI); drafting of the manuscript (RI); critical revision of the manuscript (AI, KK, HK, KS)
Correspondence: Rie Ishii, MD, PhD, Department of Ophthalmology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan. E-mail:
Received: August 01, 2014
Accepted: October 28, 2014