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Corneal Biomechanics After Intrastromal Ring Surgery: Optomechanical In Silico Assessment.

ABSTRACT: Purpose:To provide a biomechanical framework to better understand the postsurgical optomechanical behavior of the cornea after ring implantation. Methods:Calibrated in silico models were used to determine the corneal shape and stresses after ring implantation. After mechanical simulations, geometric ray-tracing was used to determine the change in spherical equivalent. The effect of the surgical procedure, circadian variation of intraocular pressure, or the biomechanical weakening introduced by keratoconus (KC) were evaluated for each intrastromal ring. Results:Models predicted the postsurgical optomechanical response of the cornea at a population level. The localized mechanical effect of the additional intrastromal volume introduced by the implants (size and diameter) drives the postsurgical corneal response. However, central corneal stresses did not increase more than 50%, and thus implants did not strengthen the cornea globally. Because of the biomechanical weakening introduced by laser pocketing, continuous implants in a pocket resulted in higher refractive corrections and in the relaxation of the anterior stroma, which could slow down KC progression. Implants can move within the stroma, acting as a dynamic pivot point that modifies corneal kinematics and flattens the corneal center. Changes in stromal mechanical properties did not impact on refraction for normal or pathological corneas. Conclusions:Implants do not stiffen the cornea but create a local bulkening effect that regularizes the corneal shape by modifying corneal kinematics without canceling corneal motion. Translational Relevance:In silico models can help to understand corneal biomechanics, to plan patient-specific interventions, or to create biomechanically driven nomograms.

SUBMITTER: Ariza-Gracia MA

PROVIDER: S-EPMC7585389 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Corneal Biomechanics After Intrastromal Ring Surgery: Optomechanical In Silico Assessment.

Ariza-Gracia Miguel Ángel MÁ Flecha-Lescún Julio J Büchler Philippe P Calvo Begoña B

Translational vision science & technology 20201021 11

<h4>Purpose</h4>To provide a biomechanical framework to better understand the postsurgical optomechanical behavior of the cornea after ring implantation.<h4>Methods</h4>Calibrated in silico models were used to determine the corneal shape and stresses after ring implantation. After mechanical simulations, geometric ray-tracing was used to determine the change in spherical equivalent. The effect of the surgical procedure, circadian variation of intraocular pressure, or the biomechanical weakening ...[more]

PMID: 33150051

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Project description:Purpose:To evaluate the outcomes of femtosecond laser-assisted implantation of a 355-degree intracorneal ring (ICR) (Keraring) in patients with keratoconus in the three-year follow-up. Setting:Future Femtolaser Center, Sohag, Egypt. Design:Prospective interventional case series. Patients and Methods:A prospective case series of 38 eyes of 26 patients with keratoconus had implantation of the 355-degree ICR keraring after tunnel creation with a femtosecond laser. The uncorrected visual acuities (UCVA) and best-corrected visual acuities (BCVA), sphere, cylinder, and manifest refraction spherical equivalent (SE), and mean keratometry (K), K max, and K min were evaluated preoperatively and 3, 6, 12, 24, and 36 months postoperatively, and all complications were reported. Results:38 eyes of 26 patients with mean age 25.92?±?5.44 years were enrolled in the study, 11 were males (42.3%). The mean UCVA improved from 0.93?±?0.21 to 0.63?±?0.21 logMAR (P ? 0.001) and the mean BCVA from 0.67?±?0.22 to 0.43?±?0.26 logMAR (P < 0.001). The mean sphere, cylinder, and spherical equivalent have been changed dramatically from preoperative to 3 month postoperative, which is statistically significant (P ? 0.001), and the changes between 1 and 2 years and 2 and 3 years are also considerable and statistically significant; the K max and K min and K mean improved and the changes were statistically significant (P ? 0.001), and the changes between one, two, and three years were also statistically significant. The safety and efficacy indices were changed through the three-year follow-up. The complications were corneal neovascularization (36.84%), corneal melting (26.3%), and ring extrusion (31.5%) at the end of the study. Conclusions:Implantation of a 355-degree intracorneal keraring using femtosecond laser improved the visual, refractive, and topographic parameters in keratoconus patients, with a high rate of ICR extrusion and instability. The study has been registered for the Pan African Clinical Trial Registry (http://www.pactr.org) database within No: PACTR201810796878908 on 29 October 2018.

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Dataset Information

Corneal Biomechanics After Intrastromal Ring Surgery: Optomechanical In Silico Assessment.

Publications

Corneal Biomechanics After Intrastromal Ring Surgery: Optomechanical In Silico Assessment.

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