June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
BIOMECHANICAL COMPARISON OF CONTRALATERAL FLAP-BASED AND NO-FLAP FEMTOSECOND LENTICULE EXTRACTION PROCEDURES USING INVERSE FINITE ELEMENT ANALYSIS
Author Affiliations & Notes
  • Ibrahim Seven
    Ophthalmic Research, Cleveland Clinic Cole Eye Institute, Cleveland, OH
  • Ali Vahdati
    Ophthalmic Research, Cleveland Clinic Cole Eye Institute, Cleveland, OH
  • Cynthia J Roberts
    The Ohio State University, Columbus, OH
  • Iben Bach Pedersen
    Aarhus University Hospital, Aarhus, Denmark
  • Jesper Hjortdal
    Aarhus University Hospital, Aarhus, Denmark
  • William J Dupps
    Ophthalmic Research, Cleveland Clinic Cole Eye Institute, Cleveland, OH
  • Footnotes
    Commercial Relationships Ibrahim Seven, Optoquest (C); Ali Vahdati, None; Cynthia Roberts, Zeiss (C), Zeiss (F); Iben Pedersen, None; Jesper Hjortdal, Zeiss (C); William Dupps, Cleveland Clinic Innovations (P), Zeiss (F)
  • Footnotes
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Investigative Ophthalmology & Visual Science June 2015, Vol.56, 1110. doi:
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      Ibrahim Seven, Ali Vahdati, Cynthia J Roberts, Iben Bach Pedersen, Jesper Hjortdal, William J Dupps; BIOMECHANICAL COMPARISON OF CONTRALATERAL FLAP-BASED AND NO-FLAP FEMTOSECOND LENTICULE EXTRACTION PROCEDURES USING INVERSE FINITE ELEMENT ANALYSIS . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1110.

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

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Abstract
 
Purpose
 

No-flap lenticule extraction procedure has been introduced in order to conserve anterior stromal collagen fibers (RELEX SMILE Carl Zeiss Meditec, Germany). Prior studies using clinical corneal stiffness measurement devices were limited to differentiate the biomechanical impact of this procedure comparing to flap based procedures. This contralateral study aims at predicting the amount of weakening in collagen fibril elasticity induced by flap-based versus no flap lenticule extraction methods.

 
Methods
 

Patient specific tomography data were meshed using a custom meshing software consisting epithelium, flap/cap, wound and residual stromal bed. A hyperelastic, anisotropic, incompressible and depth dependent material formulation was utilized for the stroma. Inverse FE analyses were performed using Abaqus 6.11 and Matlab 7.8.0 with 15mmHg intraocular pressure followed by a forward analysis using 30mmHg IOP to better demonstrate the mechanical impact of each procedure. Two cases, one myopic and one myopic astigmatism,who received flap-based and no-flap treatments contra-laterally were simulated with their clinical treatment settings. Percentage weakening in the fiber stiffness within the flap region compared to the no-flap procedure was found by preforming inverse finite element (FE) study.

 
Results
 

Flap based procedure demonstrated 68%, 71% surgically induced weakening within flap region for patient1 and patient2 respectively. Lower stress and deformation within the residual stromal bed were noted in the no-flap procedures as opposed to the flap-based procedures. Simulated refractive outcomes closely matched the 6month clinical follow-up topographies.

 
Conclusions
 

Based on the results of this study, the no-flap procedure demonstrated higher biomechanical stability following the surgery as opposed to the flap-based procedure when the same preoperative material properties were assigned to each contralateral eye.  

 
Surgically induced deformation within residual stromal bed from a single case. Comparing two procedures at two IOP levels
 
Surgically induced deformation within residual stromal bed from a single case. Comparing two procedures at two IOP levels
 
 
Surgically induced von-mises stresses within residual stromal bed from a single case. Comparing two procedures at two IOP levels
 
Surgically induced von-mises stresses within residual stromal bed from a single case. Comparing two procedures at two IOP levels

 
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