Biomechanical Properties of the Cornea Using a Dynamic Scheimpflug Analyzer in Healthy Eyes

Abstract Background To investigate machine-learning (ML) algorithms to differentiate corneal biomechanical properties between different topographical stages of keratoconus (KC) by dynamic Scheimpflug tonometry (CST, Corvis ST, Oculus, Wetzlar, Germany). In the following, ML models were used to predict the severity in a training and validation dataset. Methods Three hundred and eighteen keratoconic and one hundred sixteen healthy eyes were included in this monocentric and cross-sectional pilot study. Dynamic corneal response (DCR) and corneal thickness related (pachymetric) parameters from CST were chosen by appropriated selection techniques to develop a ML algorithm. The stage of KC was determined by the topographical keratoconus classification system (TKC, Pentacam, Oculus). Patients who were classified as TKC 1, TKC 2 and TKC 3 were assigned to subgroup mild, moderate, and advanced KC. If patients were classified as TKC 1–2, TKC 2–3 or TKC 3–4, they were assigned to subgroups according to the normative range of further corneal indices (index of surface variance, keratoconus index and minimum radius). Patients classified as TKC 4 were not included in this study due to the limited amount of cases. Linear discriminant analysis (LDA) and random forest (RF) algorithms were used to develop the classification models. Data were divided into training (70% of cases) and validation (30% of cases) datasets. Results LDA model predicted healthy, mild, moderate, and advanced KC eyes with a sensitivity (Sn)/specificity (Sp) of 82%/97%, 73%/81%, 62%/83% and 68%/95% from a validation dataset, respectively. For the RF model, a Sn/Sp of 91%/94%, 80%/90%, 63%/87%, 72%/95% could be reached for predicting healthy, mild, moderate, and advanced KC eyes, respectively. The overall accuracy of LDA and RF was 71% and 78%, respectively. The accuracy for KC detection including all subgroups of KC severity was 93% in both models. Conclusion The RF model showed good accuracy in predicting healthy eyes and various stages of KC. The accuracy was superior with respect to the LDA model. The clinical importance of the models is that the standalone dynamic Scheimpflug tonometry is able to predict the severity of KC without having the keratometric data. Trial registration NCT04251143 at Clinicaltrials.gov, registered at 12 March 2018 (Retrospectively registered).

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Biomechanical Properties of the Stifle Joint Lateral Collateral Ligament in Dogs

Veterinary and Comparative Orthopaedics and Traumatology ◽

10.1055/s-0038-1633103 ◽

1992 ◽

Vol 05 (04) ◽

pp. 158-162 ◽

Cited By ~ 1

Author(s):

D. Blackketter ◽

J Harari ◽

J. Dupuis

Keyword(s):

Mechanical Properties ◽

Cruciate Ligament ◽

Lateral Collateral Ligament ◽

Biomechanical Properties ◽

Fibular Head ◽

Joint Stability ◽

Collateral Ligament ◽

Cranial Cruciate Ligament ◽

Stifle Joint

Bone/lateral collateral ligament/bone preparations were tested and structural mechanical properties compared to properties of cranial cruciate ligament in 15 dogs. The lateral collateral ligament has sufficient stiffness to provide stifle joint stability and strength to resist acute overload following fibular head transposition.

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The influence of osteopathic correction on the rate of various rhythms of the body

Russian Osteopathic Journal ◽

10.32885/2220-0975-2019-1-2-64-71 ◽

2019 ◽

pp. 64-71 ◽

Cited By ~ 1

Author(s):

A. E. Chernikova ◽

Yu. P. Potekhina

Keyword(s):

Heart Rate ◽

Respiratory Rate ◽

Age Groups ◽

Biomechanical Properties ◽

Dispersion Analysis ◽

The Body ◽

Body Tissues ◽

Age Related ◽

Significant Difference ◽

Before And After

Introduction. An osteopathic examination determines the rate, the amplitude and the strength of the main rhythms (cardiac, respiratory and cranial). However, there are relatively few studies in the available literature dedicated to the influence of osteopathic correction (OC) on the characteristics of these rhythms.Goal of research — to study the influence of OC on the rate characteristics of various rhythms of the human body.Materials and methods. 88 adult osteopathic patients aged from 18 to 81 years were examined, among them 30 men and 58 women. All patients received general osteopathic examination. The rate of the cranial rhythm (RCR), respiratory rate (RR) heart rate (HR), the mobility of the nervous processes (MNP) and the connective tissue mobility (CTM) were assessed before and after the OC session.Results. Since age varied greatly in the examined group, a correlation analysis of age-related changes of the assessed rhythms was carried out. Only the CTM correlated with age (r=–0,28; p<0,05) in a statistically significant way. The rank dispersion analysis of Kruskal–Wallis also showed statistically significant difference in this indicator in different age groups (p=0,043). With the increase of years, the CTM decreases gradually. After the OC, the CTM, increased in a statistically significant way (p<0,0001). The RCR varied from 5 to 12 cycles/min in the examined group, which corresponded to the norm. After the OC, the RCR has increased in a statistically significant way (p<0,0001), the MNP has also increased (p<0,0001). The initial heart rate in the subjects varied from 56 to 94 beats/min, and in 15 % it exceeded the norm. After the OC the heart rate corresponded to the norm in all patients. The heart rate and the respiratory rate significantly decreased after the OC (р<0,0001).Conclusion. The described biorhythm changes after the OC session may be indicative of the improvement of the nervous regulation, of the normalization of the autonomic balance, of the improvement of the biomechanical properties of body tissues and of the increase of their mobility. The assessed parameters can be measured quickly without any additional equipment and can be used in order to study the results of the OC.

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Influence of corneal biomechanical properties on IOP indices in patients with keratoconus

The Eye ◽

10.33791/2222-4408-2019-4-15-19 ◽

2019 ◽

Vol 21 (128) ◽

pp. 15-19

Author(s):

Irina Bubnova ◽

Veronica Averich ◽

Elena Belousova

Keyword(s):

Disease Progression ◽

Corneal Thickness ◽

Central Zone ◽

Biomechanical Properties ◽

Resistance Factor ◽

Corneal Resistance Factor ◽

Mean Values ◽

Coefficient Of Elasticity ◽

D Values ◽

Corneal Biomechanical Properties

Purpose: Evaluation of corneal biomechanical prop¬erties and their influence on IOP indices in patients with keratoconus. Material and methods. The study included 194 eyes with keratoconus (113 patients aged from 23 to 36 years old). Corneal refraction in central zone varied from 48.25 to 56.75 D, values of corneal thickness ranged from 279 to 558 μm. Patients were divided into 4 groups according to Amsler classification: I stage – 40 eyes; II stage – 78 eyes; III stage – 54 eyes and IV stage – 22 eyes. Standard ophthal¬mological examination was carried out including pneumo¬tonometry. IOP indices and values of biomechanical prop¬erties were evaluated by dynamic bidirectional pneumatic applanation and pneumatic impression. Results. Study of corneal biomechanical properties in patients with keratoconus showed a decrease of such biomechanical indices as corneal hysteresis (CH) on aver¬age to 8.42±1.12 mm Hg, corneal resistance factor (CRF) – to 7.45±0.96 mm Hg, coefficient of elasticity (CE) – 5.35± 0.87 mm Hg. Values of these indices strongly depended on the stage of keratoconus. In the whole sample, the aver¬age corneal compensated IOP (IOPcc) amounted to 15.08± 2.43 mm Hg, Goldman IOP (IOPg) was 11.61±2.37 mm Hg and pneumatic tonometry IOP (IOPp) was 10.13±2.94 mm Hg. IOPcc indices didn’t have any statistically significant differ¬ence in dependence on the stage of keratoconus (р>0.473), while in process of disease progression IOPg and IOPp indi¬ces showed statistically significant decrease of mean values. Conclusion. Progression of keratoconus led to a de¬crease in corneal biomechanical properties which deter¬mine reduction of such indices as IOPg and IOPp in contrast to IOPcc.

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Effects of simvastatin on bone mass and biomechanical properties of lumbar vertebra in ovariectomized rat

Medical Engineering and Bioinformatics ◽

10.2495/meb140291 ◽

2014 ◽

Author(s):

Zhiwei Lv ◽

Yue Wang ◽

Faming Tian

Keyword(s):

Bone Mass ◽

Lumbar Vertebra ◽

Biomechanical Properties ◽

Ovariectomized Rat

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The results of the correction of hyperopia, performed by FS-LASIK technique,based on an assessment of the biomechanical properties of the cornea

Modern technologies in ophtalmology ◽

10.25276/2312-4911-2020-3-80-81 ◽

2020 ◽

pp. 80-81

Author(s):

S.M. Pikusova ◽

◽

I.L. Kulikova ◽

L.A. Avershina ◽

◽

...

Keyword(s):

Biomechanical Properties

Актуальность. Гиперметропический профильабляции, создаваемый в ходе ФемтоЛАЗИК, отличается сложной формой за счет удаления роговичной ткани в виде кольца на периферии, вследствие чего происходит увеличение оптической силы роговицы в центральной зоне. В настоящее время нет общепризнанного метода оценки напряженно-деформированного состояния роговицы после коррекции гиперметропии методом ФемтоЛАЗИК. Цель. Оценка клинико-функциональных результатов коррекции гиперметропии и математической модели биомеханических свойств роговицы с использованием эластотонометрии после ФемтоЛАЗИК. Материал и методы. Исследованы результаты коррекции гиперметропии методом ФемтоЛАЗИКу 28 пациентов (36 глаз) в возрасте от 20 до 40 лет. Оценка зрительных и рефракционных результатов оперативного вмешательства проводилась на5 день и через 1 год после операции. Также проводился анализ эластокривых, полученных на основе данных эластотонометрии, с помощью конечно-элементной модели глаза, построенной в программном пакете ANSYS, Inc. Результаты. Сфероэквивалент рефракции(СЭ) до операции в условиях циклоплегии составил +4,18±1,18 D. При расчетах параметров оперативного вмешательства закладываемый СЭ был равен +3,63±1,91 D. Через 1 год после ФемтоЛАЗИКСЭ статистически значимо снизился до -0,37±0,41(р<0,001). Индекс безопасности был равен 1,13; индекс эффективности – 0,61. Предсказуемость рефракционного эффекта через 1 год в пределах ±1,0 Dсоставила 81% случаев, в пределах ±0,5 D – 72,7%.Математическое моделирование показало, что после ФемтоЛАЗИК изгибная жесткость роговицы снижается, но увеличение эластоподъема несущественно, зависимость тонометрического ВГД от массы груза почти линейна. Выводы. Коррекция гиперметропии методом ФемтоЛАЗИК является безопасным, прогнозируемым и эффективным вмешательством с высокимиклинико-функциональными результатами. Эластотонометрия является наиболее точным методом оценки биомеханических свойств фиброзной оболочки глаза и должна применяться в дальнейших исследованиях.

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