Dataset Information

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 investigate the relationship between corneal biomechanical and ocular biometric parameters, and to explore biomechanical asymmetry between anisometropic eyes using the corneal visualization Scheimpflug technology device (Corvis ST). Methods: 180 anisometropic participants were included. Participants were divided into low (1.00≤△Spherical equivalent (SE) < 2.00D), moderate (2.00D≤△SE < 3.00D) and high (△SE ≥ 3.00D) anisometropic groups. Axial length (AL), keratometry, anterior chamber depth (ACD) and corneal biomechanical parameters were assessed using the OA-2000 biometer, Pentacam HR and Corvis ST, respectively. Results: The mean age of participants was 16.09 ± 5.64 years. Stress-Strain Index (SSI) was positively correlated with SE (r = 0.501, p < 0.001) and negatively correlated with AL (r = -0.436, p < 0.001). Some other Corvis ST parameters had weak correlation with SE or AL. Corneal biomechanical parameters except for time of first applanation (A1T), length of second applanation (A2L), deformation amplitude (DA), first applanation stiffness parameter (SPA1) and ambrosia relational thickness-horizontal (ARTh) were correlated with ametropic parameters (SE or AL) in multiple regression analyses. A1T, velocity of first applanation (A1V), time of second applanation (A2T), A2L, velocity of second applanation (A2V), corneal curvature radius at highest concavity (HCR), peak distance (PD), DA, deformation amplitude ratio max (2 mm) (DAR), SPA1, integrated radius (IR), and SSI showed significant differences between fellow eyes (p < 0.05). There was no significant difference in asymmetry of corneal biomechanics among the three groups (p > 0.05). Asymmetry of some biomechanical parameters had weak correlation with asymmetry of mean corneal curvatures and ACD. However, asymmetry of corneal biomechanical parameters was not correlated with asymmetry of SE or AL (p > 0.05). Conclusion: More myopic eyes had weaker biomechanical properties than the contralateral eye in anisometropia. However, a certain linear relationship between anisometropia and biomechanical asymmetry was not found.

Project description:Purpose:To evaluate a new tangential map-based nomogram versus the axial map-based nomogram for ICRS in keratoconus. Methods:A prospective case series study including 64 eyes of 64 patients who underwent ICRS implantation. Cone location was determined for each eye with two maps: the axial and the tangential. Appropriate ring selection was determined using two surgical nomograms: axial map-based and tangential map-based. Visual, refractive, and topographic outcomes were assessed before, as well as at 3, 6, and 12 months after ICRS implantation. Results:The cone location, and consequently the ring selection, was significantly different in the two nomograms with a "centralization tendency" in the tangential map. In the axial group, UDVA and CDVA improved from 0.12?±?0.04 and 0.24?±?0.08 to 0.28?±?0.08 and 0.4?±?0.1, respectively. Similarly, MRSE substantially decreased from -6.7?±?3.3 to -1.2?±?1.1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09?±?0.06 and 0.2?±?0.1 to 0.5?±?0.2 and 0.7?±?0.2, respectively. MRSE substantially decreased from -4.9?±?1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09?±?0.06 and 0.2?±?0.1 to 0.5?±?0.2 and 0.7?±?0.2, respectively. MRSE substantially decreased from -4.9?±?1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09?±?0.06 and 0.2?±?0.1 to 0.5?±?0.2 and 0.7?±?0.2, respectively. MRSE substantially decreased from -4.9?±?1P=0.01 ? . Similarly, the gain in the CDVA was 0.4 and 0.15 in the tangential and axial groups, respectively, at 12 months, P=0.01 ? . Similarly, the gain in the CDVA was 0.4 and 0.15 in the tangential and axial groups, respectively, at 12 months. Conclusion:The tangential map-based nomogram attained better visual and refractive outcomes at 1 year. In addition, the cone location was significantly different between both maps with a centralization tendency in the tangential one.

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.

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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