June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
A comparison of biomechanical changes after PRK, LASIK and SMILE
Author Affiliations & Notes
  • Abby Wilson
    Mechanical Engineering, University College London, London, United Kingdom
    Institute of Ophthalmology, University College London, London, United Kingdom
  • Timothy J Archer
    Reinstein Vision, London Vision Clinic, London, United Kingdom
  • Dan Z Reinstein
    Reinstein Vision, London Vision Clinic, London, United Kingdom
    Columbia University Irving Medical Center, New York, United States
  • John Marshall
    Institute of Ophthalmology, University College London, London, United Kingdom
  • Footnotes
    Commercial Relationships   Abby Wilson None; Timothy Archer None; Dan Reinstein Carl Zeiss Meditec, Code C (Consultant/Contractor), CSO Italia, Code C (Consultant/Contractor), ArcScan Inc., Code I (Personal Financial Interest); John Marshall None
  • Footnotes
    Support  Fight For Sight Grant (FFS 528121)
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 1686. doi:
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    • Get Citation

      Abby Wilson, Timothy J Archer, Dan Z Reinstein, John Marshall; A comparison of biomechanical changes after PRK, LASIK and SMILE. Invest. Ophthalmol. Vis. Sci. 2023;64(8):1686.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Several refractive surgery procedures, including, PRK, LASIK, and SMILE are now undertaken. Controversy exists regarding their biomechanical implications. PRK and SMILE, due to being flapless procedures, are hypothesized to better maintain the mechanical integrity of the cornea relative to LASIK. We performed an ex vivo interferometric study, to quantify the overall and spatial implications of PRK, LASIK and SMILE on corneal biomechanics.

Methods : Interferometric imaging was conducted on 32 porcine corneal-scleral specimens (dissected from enucleated eyes < 48hrs post-mortem), before and immediately following refractive surgery. Each cornea was mounted into an artificial anterior chamber filled with phosphate-buffered saline solution to exert a pressure on the posterior corneal surface to simulate normal IOP. Baseline pressure was set to 17mmHg. A speckle interferometric device was used to record full surface deformation maps of corneas responding to pulsatile pressure variations (17.0 – 17.5mmHg) over 50 cycles. All corneas were imaged prior to surgery. All surgeries were -3.00 diopters. Corneas underwent 1 of 4 procedures; PRK (n=8); LASIK, depth 200µm (n=8); SMILE, depth 200µm (n=8); SMILE, depth 160µm (n=8). Imaging was repeated for all corneas immediately post-surgery. Pre-surgery and post-surgery displacement maps were compared to evaluate spatial changes to corneal deformation after surgery.

Results : A total value of surface displacement was calculated for each cornea by summing the displacement at each pixel for pre-surgery and post-surgery comparison. Total surface displacement in response to pressure variations increased post-surgery for all procedures (PRK 2%, LASIK 33%, SMILE (d-200µm) 23%, SMILE (d-160µm) 11%). Surgery altered the profile of surface deformation, with high displacement concentrated at the flap boundary post-LASIK, and increased displacement in the central treatment zone post-SMILE.

Conclusions : PRK was shown to best preserve the biomechanical integrity of the cornea. SMILE appears to have biomechanical advantages over LASIK with further benefits gained when performed at a shallower depth. Further work is now required to; establish the longer-term biomechanical effects of LASIK and SMILE after a period of healing; to determine the optimum depth for SMILE surgery; and to confirm these findings in human tissue.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

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