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Postop PRK, LASIK and ReLEx® SMILE cornea biomechanical models

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Session Details

Session Title: Presented Poster Session: Cornea III

Venue: Poster Village: Pod 2

First Author: : A.Kachanov RUSSIA

Co Author(s): :    S. Bauer   B. Zimin           

Abstract Details

Purpose:

To develop biomechanical models of the cornea after modern refractive surgery - PRK, LASIK with mechanical microkeratome (M-LASIK), “femto-laser” assisted LASIK (F-LASIK), PRK and SMILE.

Setting:

1 - St.-Petersburg branch of Sv. Fyodorov “Eye Microsurgery Clinic”; 2 – North-Western State Medical University named after I.I. Mechnikov; 3 - St.-Petersburg State University; 4 – The Laboratory of Hydroelasticity, Russian Institute of Problems of Mechanical Engineering. St.-Petersburg, Russia.

Methods:

We’ve made the following post-op cornea biomechanical models: M-LASIK – central corneal thickness (CCT) - 540 microns, average flap thickness – 130 microns, ablation depth (AD) – 100 microns; F-LASIK – CCT - 540 microns, average flap thickness – 90 microns, AD – 100 microns; PRK – CCT - 540 microns, and AD – 100 microns; SMILE – CCT - 540 microns, lenticule thickness – 100 microns. And we should consider the residual stromal layers above and below the lenticule interface for SMILE (Reinstein D. et al., 2013).

Results:

In our study residual stromal thickness (RST) was 310 microns after M-LASIK (≈57% of initial CCT), and 350 microns after F-LASIK (≈65% of initial CCT); RST after PRK was 440 microns (≈82% of initial CCT), and residual stromal and layers thickness above and below the lenticule interface after SMILE was 440 microns also (≈82% of initial CCT). When the shell thickness is reduced by 2 times - bending stiffness decreases 8 times (!) (Timoshenko S.P. and Woinowsky-Krieger S.,1959), and cornea becomes more weaker (e.g. after LASIK).

Conclusions:

With considering above-mentioned models after M-LASAIK RST remains just over 50% of its original thickness. But after PRK and ReLEx® SMILE cornea remains more stronger, uniform and resistant to mechanical stress, because it remains approximately 82% of its original thickness. It can be expected that corneal ectasia after PRK and SMILE is much less common than after LASIK surgery. Consequently, SMILE and PRK should be more safer methods for ametropia correction.

Financial Disclosure:

NONE

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