Comparative analysis of two different types of intracorneal implants in keratoconus: A corneal tomographic study

Sedaghat, Mohammad Reza; Momeni‐Moghaddam, Hamed; Belin, Michael W.; Piñero, David P.; Akbarzadeh, Reyhaneh; Ambrósio, Renato; Hosseini, Seyed Rafi

doi:10.1177/1120672120963449

Cited by 4 publications

(3 citation statements)

References 27 publications

(34 reference statements)

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“…While there was good agreement between the clinical results and the numerical analysis results for Kera355 with both implementation methods, the pocket method induced a higher flattening effect compared with the tunnel incision method. A recent clinical study [35] also confirmed that the pocket method could generally achieve greater regulation of corneal shape, though several factors could still influence this fact, such as the degree of disease, the initial structure of the cornea, and the generated interactions between ICRS and the cornea. From mechanical perspective, in the severe form of keratoconus in which patients suffer severely from tissue degeneration, the pocket incision eliminates intrastromal tissue constancy and strength.…”

Section: Effect Of Icrs On Corneal Deformations and Shape Regularization (Fem Validation)mentioning

confidence: 94%

Effects of intracorneal ring segments on the biomechanical response of the ectatic cornea to air-puff: A patient-specific numerical analysis

Bagheri

Mosaddegh

Kadkhodaei

2021

Mathematics and Mechanics of Solids

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The assessment of the underlying factors that influence the biomechanics and dynamics of the cornea is essential for preserving the safety and efficacy of refractive surgeries. In the present work, the operated cornea with intracorneal ring segments (ICRSs) in a patient-specific finite-element model (FEM) was subjected to the air-puff. Then, the dynamic deformation parameters predicted by the FEM were obtained and compared with the corresponding values in clinical measurements. In this study, the effects of ICRS design, position, and implementation procedure in six different surgical scenarios were examined on the induced corneal stresses, deformation behavior, and shape regularization. While surgical scenarios with arc lengths of 160° (single and double segment), 355° implemented with the tunnel incision method provided similar maximum apical displacement (MAD) and highest concavity radius of curvature HCR), they induced significantly different flattening effects. The surgical scenarios with the segment of 160° arc-length implemented in nasal–temporal direction showed an approximately 15% higher reduction in mean corneal power ([Formula: see text]) value than the superior–inferior direction. From a solid-mechanics perspective, the study of ICRS mechanics in the cornea also confirmed the importance of the implementation position to achieve satisfactory flattening outcomes. Comparison of the two types of ICRS implementation procedures showed that, although the pocket method demonstrated a 10.23% higher MAD, it induced a higher reduction in the HCR of 21.65% compared with tunnel incision. The developed numerical model demonstrated the direct correlation of the ICRS insertion site with induced contact stresses and ICRS position stability. The study hypothesizes the significant influence of ICRS implementation position and procedure on the corneal biomechanical and dynamical behaviors. The proposed approach can be assessed as a robust and novel framework for planning optimized corneal refractive surgeries.

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Section: Effect Of Icrs On Corneal Deformations and Shape Regularization (Fem Validation)mentioning

confidence: 94%

Effects of intracorneal ring segments on the biomechanical response of the ectatic cornea to air-puff: A patient-specific numerical analysis

Bagheri

Mosaddegh

Kadkhodaei

2021

Mathematics and Mechanics of Solids

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“…Furthermore, postoperative changes in vision do not regularly correlate with geometric improvements in the cornea [14]. Numerous studies have attempted to determine the relationship between various factors and surgical outcomes to avoid unsatisfactory results [4,7,11,13,[15][16][17][18][19][20][21][22][23][24][25][26]. However, the impact of these factors on ICRS-induced visual outcomes remains inconclusive, and some factors reportedly increase the risk of post-implantation complications.…”

Section: Introductionmentioning

confidence: 99%

Factors predicting the visual outcome of intracorneal ring segment for keratoconus

Khanthik,

Kasetsuwan,

Yaisawang

et al. 2024

PLoS ONE

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Objectives To identify predictive factors and to construct predictive models using epidemiological and clinical preoperative factors for the visual acuity change after intracorneal ring segment (ICRS) implantation in patients with keratoconus. Methods The medical records of 287 keratoconic eyes of 230 patients implanted with ICRS at Chula Refractive Surgery Center of a tertiary university hospital (Bangkok, Thailand) between January 2012 and March 2022 were retrospectively reviewed for epidemiological and clinical preoperative variables, including those derived from Scheimpflug tomography. After randomly excluding one eye for each bilateral case, the remaining 230 eyes were randomized into two groups: a training group (184 eyes) and a validation group (46 eyes). In the training group, the correlation between the interesting variables and postoperative uncorrected and corrected distance visual acuity change (ΔUDVA and ΔCDVA; logMAR scale) at 6 months was explored, and then the multiple linear regression analysis was used to develop the predictive models. The obtained models were tested using the validation group. Results There were 5 and 14 preoperative variables that statistically correlated with ΔUDVA and ΔCDVA respectively. Only the preoperative corrected distance visual acuity (CDVAp) strongly correlated with ΔCDVA (Beta = -0.746). Using multiple regression, the preoperative uncorrected distance visual acuity (UDVAp) and front mean keratometry were selected in the proposed model for ΔUDVA (adjusted R2 = 38.8%), while the CDVAp and index of surface variance (ISV) were selected in the model ΔCDVA=−0.043−0.613×CDVAp+0.002×ISV (adjusted R2 = 48.9%). The ΔUDVA and ΔCDVA models were correct in 47.83% and 63.4% of the validation group within 0.20 logMAR, respectively. Conclusions Potential predictive factors and models for ICRS-induced changes in visual acuity are proposed as adjunctive tools for clinicians. Such tools could be used for case selection and during counselling before ICRS implantation to maximize surgical outcomes.

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Section: Introductionmentioning

confidence: 99%

Factors predicting the visual outcome of intracorneal ring segment for keratoconus

Khanthik,

Yaisawang,

Puangsricharern

et al. 2023

Preprint

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Objectives: To find predictive factors and to construct predictive models using epidemiological and clinical preoperative factors for the visual acuity change after intracorneal ring segment (ICRS) implantation in keratoconus patients. Methods: Medical records of 287 keratoconic eyes implanted with ICRS at Chula Refractive Surgery Centre of a tertiary university hospital (Bangkok, Thailand) between January 2012 and March 2022 were retrospectively reviewed for epidemiological and clinical preoperative variables, including those derived from Scheimpflug tomography. The correlation between these variables and postoperative uncorrected and corrected distance visual acuity change (ΔUDVA and ΔCDVA; logMAR scale) at 6 months was explored. Two hundred forty eight eyes (excluding cases with unmeasurable refraction) were randomized into 2 groups: the equation group (198 eyes) and the validation group (50 eyes). Multiple linear regression analysis was used to develop the predictive model from the equation group. Results: Twenty preoperative variables were statistically correlated with ΔCDVA. Only the preoperative corrected distance visual acuity (CDVAp) strongly correlated with ΔCDVA (R = -0.746). ΔUDVA correlated with only preoperative visual acuity, corneal astigmatism, and maximum Ambrósio relational thickness (ARTmax). CDVAp, spherical power (SPH), and anterior minimum sagittal curvature (Rmin) were the best predictors of ΔCDVA. The proposed model, ΔCDVA = 0.589 - 0.713×CDVAp - 0.010×SPH - 0.082×Rmin, had an acceptable predictability (R2 = 53.4%). The prediction was correct in 82% of the eyes within 0.22 logMAR. Conclusions: Potential predictive factors and models for ICRS-induced changes in visual acuity were proposed as adjunctive tools for clinicians. Such tools could be used for case selection and during counseling before ICRS implantation to maximize surgical outcomes.

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Comparative analysis of two different types of intracorneal implants in keratoconus: A corneal tomographic study

Cited by 4 publications

References 27 publications

Effects of intracorneal ring segments on the biomechanical response of the ectatic cornea to air-puff: A patient-specific numerical analysis

Effects of intracorneal ring segments on the biomechanical response of the ectatic cornea to air-puff: A patient-specific numerical analysis

Factors predicting the visual outcome of intracorneal ring segment for keratoconus

Factors predicting the visual outcome of intracorneal ring segment for keratoconus

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