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Corneal subbasal nerve density and sensation after ReLEx FLEX and ReLEx SMILE

Poster Details

First Author: A.Vestergaard DENMARK

Co Author(s):    K. Grønbech   J. Grauslund   A. Sjølie   A. Ivarsen   J. Hjortdal  

Abstract Details


ReLEx flex (flex) and ReLEx smile (smile) are two relatively new corneal refractive procedures, where a stromal lenticule is cut by a femtosecond laser and manually extracted. The purpose of this study was to compare corneal subbasal nerve fiber density and corneal sensation in patients with moderate to high myopia treated with flex or smile.


Vestergaard A.H.1, Grønbech K. 1, Grauslund J.1, Sjølie A.K.1, Ivarsen A.2, Hjortdal J.2 1. Department of Ophthalmology, Odense University Hospital, Denmark. 2. Department of Ophthalmology, Aarhus University Hospital, Denmark.


A prospective randomized study of 26 patients treated with flex in one eye, and smile in the other at the Department of Ophthalmology, Aarhus University Hospital. Preoperative spherical equivalent refraction averaged -7.50 D (range -6.00 to -9.75 D) in both groups. All patients had stable myopia and no other ocular diseases. A VisuMax® femtosecond laser (Carl Zeiss Meditec, Jena, Germany) was used. Lenticule diameters were the same in both eyes and ranged from 6.00 to 6.50 mm. Flap thickness was 110 to 120 ṁm, and flap/cap diameter ranged from 7.3 to 8.0 mm. Images of the subbasal corneal nerves were acquired by continuous through-focusing of the cornea using in vivo confocal laser-scanning microscopy (Heidelberg Engineering, Heidelberg, Germany). The detachable objective, the so called “Rostock cornea module (RCM)”, was used to optimize image acquisition. The NeuronJ Java program ( was used to trace and quantify subbasal nerves. Mean central corneal nerve density was calculated from nerve tracings from 4 images of each eye, evaluated by a single masked investigator. Mean central corneal sensation was measured in filament length (cm) using Cochet-Bonnet esthesiometry (Luneau Ophtalmologie, Chartres, France) with 4 measurements of each eye. Patients were examined before and 6 months after surgery.


Mean subbasal nerve density before surgery was 16.88 ±4.74 mm/mm2 in flex eyes and 16.01 ±4.70 mm/mm2 in smile eyes (p=0.509). Six months after surgery, a statistically significant reduction in nerve density were found in both flex eyes (4.87 ±4.13 mm/mm2; p<0.001) and smile eyes (8.86 ±5.53 mm/mm2; p<0.001). When comparing mean nerve density after 6 months, a borderline significant difference was found in favor of smile eyes (p=0.050). Mean central corneal sensation before surgery was 5.86 ±0.20 cm in flex eyes and 5.86 ±0.21 cm in smile eyes (p=0.806). Six months after surgery, a statistically significant reduction in corneal sensation was found in flex eyes (5.47 ±0.45 cm; p<0.001), and a non-significant reduction was found in smile eyes (5.75 ±0.36 cm; p=0.325). When comparing mean corneal sensation after 6 months, a significant difference was found in favor of smile (p<0.011).


The less invasive ReLEx smile technique seemed better at sparing the central corneal nerves as compared to ReLEx flex. Six months after refractive lenticule extraction, subbasal nerve density was reduced in both flex and smile eyes, but less in smile eyes. Corneal sensation was reduced in flex eyes and unchanged in smile eyes.

Financial Disclosure:

... travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented

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