Predicting the unpredictable with a novel computational method: corneal biomechanics after refractive surgery

Session Details

Session Title: Medical Cornea & Biomechanics

Session Date/Time: Sunday 23/09/2018 | 08:00-10:00

Paper Time: 08:51

Venue: Room A3, Podium 3

First Author: : M.Francis INDIA

Co Author(s): :    P. Khamar   R. Dalal   R. Chandapura   R. Shetty   R. Nuijts   A. Sinha Roy     

Abstract Details

Purpose:

In-vivo corneal biomechanics is currently evaluated using air-puff applanation deformation amplitude waveform (DAW). This study aimed to predict post surgery DAW and corneal stiffness (kc; unit = N/m) by using preoperative (pre-op) biomechanics, pre-op corneal structure and planned refractive correction. The study focused on surgical techniques such as small incision lenticule extraction (SMILE), LASIK (laser-assisted in-situ keratomileusis) and PRK (photorefractive keratectomy).

Setting:

The study was conducted at Narayana Nethralaya Eye Hospital, Bangalore, India. Surgeries were performed using VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Germany), WaveLight FS200 femtosecond laser and WaveLight EX500 excimer laser platform (Alcon Laboratories, USA).

Methods:

Total of 24 eyes were selected (8 per technique) to undergo predictive modelling and validation using the Corvis-ST and Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) data. The model calculated the pre-op material property of cornea using finite element modelling (FEM) approach, pre-op DAW (from Corvis-ST) and pre-op custom-made mesh geometry (from Pentacam HR). FEM then calculated post-op DAW using an altered mesh geometry based on planned refractive correction and pre-op material property. The predicted post-op DAW was used in calculating kc. Then, it was compared to the in-vivo post-op measurement.

Results:

SMILE post-op in-vivo and predicted kc values were 91.42 ± 1.59 (mean ± standard error of the mean) and 90.26 ± 1.68 N/m respectively. LASIK post-op in-vivo and predicted kc values were 93.99 ± 3.65 and 92.71 ± 4.04 N/m respectively. PRK post-op in-vivo and predicted kc values were 97.06 ± 2.09 and 96.37 ± 4.04 N/m respectively. The intra-class correlation coefficient (ICC) between predicted and in vivo post-op corneal stiffness was 0.98, 0.96 and 0.85 for SMILE, LASIK and PRK, respectively. Similarly, predicted peak deformation amplitude also had an ICC greater than 0.95 for all above surgical techniques.

Conclusions:

The study was able to predict kc, DAW and peak deformation amplitude for SMILE, LASIK and PRK with high relative correlation to the in-vivo data. Such a novel, clinically viable, highly accurate post-op refractive biomechanics prediction model has never been demonstrated before. This foresight could be a game changer in refractive surgery segment.

Financial Disclosure:

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