Regional variation in the biomechanical properties of the human sclera

Elsheikh, Ahmed; Geraghty, Brendan; Alhasso, Daad; Knappett, Jonathan; Campanelli, Marino; Rama, Paolo

doi:10.1016/j.exer.2010.02.010

Cited by 126 publications

(123 citation statements)

References 24 publications

Supporting

Mentioning

111

Contrasting

Unclassified

Order By: Relevance

“…Finally, Figure 20 depicts the thickness evolution with pressure. The thickness decreases continuously, with the rate of reduction greater at the beginning, and this was also reported by Elsheikh et al (2010). At high pressure levels the thickness decreases slowly, reaching a constant value of 0.52 mm near the optic nerve (zone 5 in Figure 14).…”

Section: Application To a Biomechanical Analysis Of Human Eye Tissuessupporting

confidence: 54%

“…In the present work, the constants of the Yeoh model are determined from the experimental results of the simple stress tests reported by Elsheikh et al (2010) for the sclera and byElsheikh et al (2008) for the cornea, both of them on healthy human tissues. The corresponding curves fitted by least squares to the Yeoh model are presented in Figures 12 and 13.…”

Section: Application To a Biomechanical Analysis Of Human Eye Tissuesmentioning

confidence: 99%

“…Due to the harmful effect of the high intraocular pressure that occurs in the disease called glaucoma (Ruiz -Ederra et al, 2005;Norman et al, 2010), different experimental (e.g., Schultz et al, 2008;Elsheikh et al, 2010;Elsheikh et al, 2008) as well as numerical (e.g., Belleza et al, 2000;Lari et al, 2012;Asejczyk et al, 2011) studies have been proposed to determine the mechanical characteristics of the sclera Elsheikh et al, 2010;Schultz et al, 2008) and the cornea (e.g., Elsheikh et al, 2008) and, in addition, to establish the state of the stress on the walls of the eyeballs subjected to an internal pressure (Belleza et al, 2000).…”

Section: Application To a Biomechanical Analysis Of Human Eye Tissuesmentioning

confidence: 99%

See 2 more Smart Citations

Numerical Simulation and Experimental Validation of the Inflation Test of Latex Balloons

Bustos

Herrera

Celentano

et al. 2016

Lat. Am. j. solids struct.

View full text Add to dashboard Cite

Experiments and modeling aimed at assessing the mechanical response of latex balloons in the inflation test are presented. To this end, the hyperelastic Yeoh material model is firstly characterized via tensile test and, then, used to numerically simulate via finite elements the stress-strain evolution during the inflation test. The numerical pressure-displacement curves are validated with those obtained experimentally. Moreover, this analysis is extended to a biomedical problem of an eyeball under glaucoma conditions.

show abstract

Section: Application To a Biomechanical Analysis Of Human Eye Tissuessupporting

confidence: 54%

Section: Application To a Biomechanical Analysis Of Human Eye Tissuesmentioning

confidence: 99%

Section: Application To a Biomechanical Analysis Of Human Eye Tissuesmentioning

confidence: 99%

See 1 more Smart Citation

Numerical Simulation and Experimental Validation of the Inflation Test of Latex Balloons

Bustos

Herrera

Celentano

et al. 2016

Lat. Am. j. solids struct.

View full text Add to dashboard Cite

show abstract

“…Sclera mechanical properties have been characterized on dissected tissue specimens using uniaxial [11][12][13][14][15][16] or biaxial mechanical tests [17]. These studies have demonstrated that the mechanical behavior of the sclera is typically nonlinear, viscoelastic and anisotropic.…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic Measurement of Scleral Cross-Sectional Strains During Elevations of Intraocular Pressure: Method Validation and Initial Results in Posterior Porcine Sclera

Tang

Liu

2012

Journal of Biomechanical Engineering

View full text Add to dashboard Cite

Background. Scleral biomechanical properties may be important in the pathogenesis and progression of glaucoma. The goal of this study is to develop and validate an ultrasound method for measuring cross-sectional distributive strains in the sclera during elevations of intraocular pressure (IOP). Method of Approach. Porcine globes (n ¼ 5) were tested within 24 hs postmortem. The posterior scleral shells were dissected and mounted onto a custom-built pressurization chamber. A high-frequency (55-MHz) ultrasound system (Vevo660, VisualSonics Inc., Toronto) was employed to acquire the radio frequency data during scans of the posterior pole along both circumferential and meridian directions. The IOP was gradually increased from 5 to 45 mmHg. The displacement fields were obtained from correlation-based ultrasound speckle tracking. A least-square strain estimator was used to calculate the strains in both axial and lateral directions. Experimental validation was performed by comparing tissue displacements calculated from ultrasound speckle tracking with those induced by an actuator. Theoretical analysis and simulation experiments were performed to optimize the ultrasound speckle tracking method and evaluate the accuracy and signal-to-noise ratio (SNR) in strain estimation. Results. Porcine sclera exhibited significantly larger axial strains (e.g., À5.1 6 1.5% at 45 mmHg, meridian direction) than lateral strains (e.g., 2.2 6 0.7% at 45 mmHg, meridian direction) during IOP elevations (P's < 0.01). The strain magnitudes increased nonlinearly with pressure increase. The strain maps displayed heterogeneity through the thickness. The lateral strains were significantly smaller in the circumferential direction than the meridian direction at 45 mmHg (P < 0.05). Experimental validation showed that the ultrasound speckle tracking method was capable of tracking displacements at the accuracy of sub-micron to micron. Theoretical analysis predicted the dependence of the strain estimation SNR on the strain level, as well as signal processing parameters such as kernel size. Simulation results showed that ultrasound speckle tracking had a high accuracy for estimating strains of 1-5% and a high SNR for strains of 0.5-5%. Conclusions. A new experimental method based on ultrasound speckle tracking has been developed for obtaining cross-sectional strain maps of the posterior sclera. This method provides a useful tool to examine distributive strains through the thickness of the sclera during elevations of IOP.

show abstract

“…Sclera thickness in our specimens ranged between 900 and 1,060 m in the SCR (mean: 986 m) and between 800 and 1,200 m (mean: 971 m) in the SPS without a statistically significant difference between both sclera regions. However, a recent study by Elsheikh et al [14] in human donor eyes, investigating the variation in thickness and biomechanical properties between different regions of the human sclera, observed a significant thickness shift from the maximum at the posterior pole to the minimum close to the equator, and increasing again towards the limbus. With reference to specific stress levels, the scleral stiffness showed a progression from the posterior region towards the limbus, suggesting that the posterior region's low mechanical stiffness is partly balanced by a large thickness, giving the area surrounding the lamina cribrosa and the ONH more adequate resistance to loading [14] .…”

Section: Discussionmentioning

confidence: 99%

Biomechanical and Morphological Differences between the Sclera Canal Ring and a Peripheral Sclera Ring in the Porcine Eye

Terai

Schlötzer‐Schrehardt²,

Spoerl³

et al. 2011

Ophthalmic Res

View full text Add to dashboard Cite

Aim: To investigate a possible association between the biomechanical load and unload behaviour and the elastin content of the sclera canal ring (SCR) and a superiorly localized sclera ring (SPS) in the porcine eye. Methods: Two sclera rings were trephined from each of 40 porcine eyes, one containing the SCR and the other an SPS. The load and the unload curves were measured in the extension range of 0–2.0 mm by a biomaterial tester. Hysteresis was determined from the area enclosed by the loading and unloading curve. Histochemical staining with resorcin-fuchsin and morphometric analysis of paraffin-embedded sections of both rings were performed to detect the area occupied by elastin fibres. Results: At 1 mm extension, the mean load of the SCR was 0.89 ± 0.22 N and that of the SPS 1.13 ± 0.19 N, which was not significantly different between both rings (p > 0.05). Mean hysteresis in the SCR was 1.55 ± 0.30 N × mm and 1.90 ± 0.18 N × mm in the SPS, which was significantly different between both rings (p = 0.01). Mean sclera thickness was 986 µm in the SCR (range: 900–1,060 µm) and 971 µm in the SPS (range: 800–1,200 µm) without a statistically significant difference between both sclera rings (p = 0.78). The area occupied by elastin fibres was 15.5 ± 3.4% in the SCR and 4.5 ± 1.5% in the SPS, which was significantly different between both rings (p = 0.0001). Conclusion: Hysteresis in the SCR was significantly lower than in the SPS, indicating a higher elasticity of the SCR in the porcine eye. This effect could be explained by a higher content of elastin in the surrounding ring of the peripapillary optic nerve head providing reversible contraction in cases of intra-ocular pressure variations.

show abstract

Regional variation in the biomechanical properties of the human sclera

Cited by 126 publications

References 24 publications

Numerical Simulation and Experimental Validation of the Inflation Test of Latex Balloons

Numerical Simulation and Experimental Validation of the Inflation Test of Latex Balloons

Ultrasonic Measurement of Scleral Cross-Sectional Strains During Elevations of Intraocular Pressure: Method Validation and Initial Results in Posterior Porcine Sclera

Biomechanical and Morphological Differences between the Sclera Canal Ring and a Peripheral Sclera Ring in the Porcine Eye

Contact Info

Product

Resources

About