Corneal biomechanical properties after LASIK, ReLEx flex, and ReLEx smile by Scheimpflug-based dynamic tonometry

  • Iben Bach PedersenEmail author
  • Sashia Bak-Nielsen
  • Anders Højslet Vestergaard
  • Anders Ivarsen
  • Jesper Hjortdal
Refractive Surgery



To evaluate corneal biomechanical properties after LASIK, ReLEx flex, and the flap-free procedure ReLEx smile by Scheimpflug-based dynamic tonometry (Corvis ST) and non-contact differential tonometry (Ocular Response Analyzer, ORA).


Patients treated for high myopia (−10.5 to −5.5 diopters, spherical equivalent refraction) more than one year previously at Aarhus University Hospital were included. Treatments comprised LASIK (35 eyes), ReLEx flex (31 eyes), and ReLEx smile (29 eyes). A control group included 31 healthy eyes. Cornea-compensated IOP (IOPcc), corneal hysteresis (CH), and corneal resistance factor (CRF) were measured with ORA. Corneal applanation and deformation were registered with Corvis ST during an air-pulse.


Multiple linear regression analysis showed that CH and CRF were significantly lower after all keratorefractive procedures compared to healthy controls (p < 0.05). No significant differences were observed in CH or CRF between the keratorefractive groups. Corvis ST showed no differences in radius at highest concavity (HC radius), time until first applanation (A1 Time), time until second applanation (A2 Time), and deflection length at highest concavity (HC deflection length) between groups. LASIK treated eyes had significantly shorter time until highest concavity than eyes treated with ReLEx smile (HC Time, p = 0.01). The A1 deflection length was significantly shorter in the keratorefractive groups compared to the healthy controls (p < 0.05).


Keratorefrative procedures alter the corneal biomechanical properties with regard to corneal hysteresis and corneal resistant factor. The flap-based LASIK and ReLEx flex and the flap-free ReLEx smile result in similar reduction in corneal biomechanics when evaluated by Corvis ST and ORA.


Myopia Biomechanics Laser In Situ Keratomileusis Corneal Stroma Corvis ST Ocular Response Analyzer 


Financial support

The study was supported by Fight for Sight, Denmark. The Pentacam HR and the Ocular Response Analyzer were kindly donated by Bagenkop-Nielsens Myopia Foundation.


No author has a financial or proprietary interest in any material or method mentioned. Jesper Hjortdal, MD PhD, has received travel reimbursements from Carl Zeiss Meditec.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Iben Bach Pedersen
    • 1
    Email author
  • Sashia Bak-Nielsen
    • 1
  • Anders Højslet Vestergaard
    • 2
  • Anders Ivarsen
    • 1
  • Jesper Hjortdal
    • 1
  1. 1.Department of OphthalmologyAarhus University HospitalAarhus CDenmark
  2. 2.Department of OphthalmologyOdense University HospitalOdense CDenmark

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