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Detection of corneal biomechanical changes using the ocular response analyzer: a contralateral comparison of eyes treated with ReLEx FLEX and ReLEx SMILE for moderate to high myopia

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Session Details

Session Title: Presented Poster Session: Refractive

Venue: Poster Village: Pod 3

First Author: : P.Rævdal DENMARK

Co Author(s): :    A. Iversen   J. Hjortdal   A. Vestergaard                 

Abstract Details


ReLEx FLEx (FLEX) and ReLEx SMILE (SMILE) are two relatively new corneal refractive proce-dures, where a stromal lenticule is cut by a femtosecond laser and manually extracted. FLEX is a flap-based technique where SMILE is a cap-based refractive technique without flap-creation, which in the-ory should preserve more of the corneal integrity than flap-based techniques due to the fiber-sparing anterior stromal cut. However, both procedures induce corneal weakening due to the removal of cor-neal tissue. The purpose of this study was to compare if the 37 waveform parameters measured by the Ocular Response Analyzer (ORA) were different between the two techniques.


Department of Ophthalmology, Aarhus University Hospital, Denmark.


A prospective study of 34 patients treated with FLEX in one eye, and SMILE in the other. Preopera-tive spherical equivalent refraction averaged -7.50 D (range -6.00 to -9.75 D) with a maximal astigma-tism of -1.75 D in both groups. All patients were eye healthy except stable myopia. An ORA (Reichert Ophthalmic Instruments, Depew, NY, USA) was used to assess information about corneal biomechanical properties during corneal deformation. ORA software was used to measure 37 wave-form-based parameters before and 6 months after surgery in an attempt to quantify changes in corneal biomechanical properties.


No significant difference between FLEX and SMILE was found at baseline nor after 6 months for all 37 parameters. Also, no difference was found when the change in each parameter between the preoperative to 6 months postoperative values from both groups was compared, and p-values were corrected for multi-ple comparrisons (Bonferroni method). However, a significant difference was found for the majority of all 37 parameters in both the FLEX group and the SMILE group, when preoperative and 6 months data were compared.


The 37 waveform parameters from the ORA were not able to detect any major differences between the flap-based FLEX procedure and the cap-based SMILE procedure. However, several of the waveform parameters were significantly reduced after both procedures, indicating a weakening of corneal strength as previously demonstrated by other biomechanical parameters

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