Age-related variations in the biomechanical properties of human sclera

Geraghty, Brendan; Jones, Stephen; Rama, Paolo; Akhtar, Riaz; Elsheikh, Ahmed

doi:10.1016/j.jmbbm.2012.10.011

Cited by 114 publications

(89 citation statements)

References 52 publications

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“…23,38 One possible explanation is that this is due to the dependence of corneal modulus of elasticity on the magnitude of tissue strain, but since our study was cross-sectional, we cannot determine causation. Unlike previous studies of cadaver eyes, 23,39 we did not find a relationship between Young’s modulus and subject age, likely because of our small sample size and clustering of our subjects in a fairly narrow age range (mean 51.4 ± 7.2 years; range 43–64 years). We also did not find a relationship between the modulus of elasticity and central corneal thickness or axial length.…”

Section: Discussioncontrasting

confidence: 99%

In Vivo Noninvasive Measurement of Young’s Modulus of Elasticity in Human Eyes: A Feasibility Study

Sit

Lin

Kazemi

et al. 2017

Journal of Glaucoma

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Purpose Abnormal ocular biomechanical properties may be important for understanding the risk of glaucoma. However, there are no clinical methods for measuring standard material properties in patients. In this feasibility study we demonstrated proof-of-principle for a novel method, ultrasound surface wave elastography (USWE), to determine the in vivo Young’s modulus of elasticity of corneas in normal human eyes. Methods Twenty eyes of 10 healthy subjects (mean age 51.4 ± 7.2; ± SD, range 43–64 years) were studied. A spherical-tipped probe (3-mm diameter) was placed on closed eyelids and generated a gentle harmonic vibration at 100 Hz for 0.1 second. Wave speed propagation in the cornea was measured by USWE, and Young’s modulus was calculated from the wave speed. Associations between Young’s modulus and intraocular pressure (IOP), age, central corneal thickness, and axial length were explored by Pearson correlation. Statistical significance was determined by using generalized estimating equation models to account for possible correlation between fellow eyes. Results Mean IOP was 12.8 ± 2.7 mmHg. Mean wave speed in the cornea was 1.82 ± 0.10 m/s. Young’s modulus of elasticity was 696 ± 113 kPa and was correlated with IOP (r=0.57; p=0.004), but none of the other variables (p>0.1). Conclusions USWE is a novel non-invasive technique for measuring ocular biomechanical properties. Corneal Young’s modulus in normal eyes is associated with IOP, consistent with measurements in cadaver eyes. Further work is needed to determine elasticity in other ocular tissues, particularly the sclera, and if elasticity is altered in glaucoma patients.

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Section: Discussioncontrasting

confidence: 99%

In Vivo Noninvasive Measurement of Young’s Modulus of Elasticity in Human Eyes: A Feasibility Study

Sit

Lin

Kazemi

et al. 2017

Journal of Glaucoma

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“…An increase in glycation of collagen fibrils with age may be a factor in increasing their cross-sectional area (Keeley et al, 1984; Malik et al, 1992). Increased mechanical stiffness of the sclera with age has been reported in human (Avetisov et al, 1984; Friberg and Lace, 1988; Coudrillier et al 2012; Geraghty et al, 2012), monkey (Girard et al, 2009), and mouse (Myers et al, 2010), in part due to increasing intermolecular collagen crosslinking with age (Curtin, 1969; Ihanamaki et al, 2001; Girard et al, 2009). Fazio et al (2013) showed that the strains in the peripapillary sclera were significantly lower in older human specimens.…”

Section: Introductionmentioning

confidence: 93%

Experimental scleral cross-linking increases glaucoma damage in a mouse model

Kimball

Nguyen

Steinhart

et al. 2014

Experimental Eye Research

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The purpose of this study was to assess the effect of a scleral cross-linking agent on susceptibility to glaucoma damage in a mouse model. CD1 mice underwent 3 subconjunctival injections of 0.5 M glyceraldehyde (GA) in 1 week, then had elevated intraocular pressure (IOP) induced by bead injection. Degree of cross-linking was measured by enzyme-linked immunosorbent assay (ELISA), scleral permeability was measured by fluorescence recovery after photobleaching (FRAP), and the mechanical effects of GA exposure were measured by inflation testing. Control mice had buffer injection or no injection in 2 separate glaucoma experiments. IOP was monitored by Tonolab and retinal ganglion cell (RGC) loss was measured by histological axon counting. To rule out undesirable effects of GA, we performed electroretinography and detailed histology of the retina. GA exposure had no detectable effects on RGC number, retinal structure or function either histologically or electrophysiologically. GA increased cross-linking of sclera by 37% in an ELISA assay, decreased scleral permeability (FRAP, p = 0.001), and produced a steeper pressure—strain behavior by in vitro inflation testing. In two experimental glaucoma experiments, GA-treated eyes had greater RGC axon loss from elevated IOP than either buffer-injected or control eyes, controlling for level of IOP exposure over time (p = 0.01, and 0.049, multivariable regression analyses). This is the first report that experimental alteration of the sclera, by cross-linking, increases susceptibility to RGC damage in mice.

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“…Additionally, with increasing age, the sclera increases in stiffness, due to the accumulation of nonenzymatic glycation-type cross-links of collagen fibrils with age (Coudrillier et al, 2012; Schultz et al, 2008). This age-related increase in stiffness is greatest in the anterior sclera, followed by the equatorial and then posterior sclera (Geraghty et al, 2012). …”

Section: Development Of the Scleramentioning

confidence: 99%

The dynamic sclera: Extracellular matrix remodeling in normal ocular growth and myopia development

Harper

Summers

2015

Experimental Eye Research

201

129

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Myopia is a common ocular condition, characterized by excessive elongation of the ocular globe. The prevalence of myopia continues to increase, particularly among highly educated groups, now exceeding 80% in some groups. In parallel with the increased prevalence of myopia, are increases in associated blinding ocular conditions including glaucoma, retinal detachment and macular degeneration, making myopia a significant global health concern. The elongation of the eye is closely related to the biomechanical properties of the sclera, which in turn are largely dependent on the composition of the scleral extracellular matrix. Therefore an understanding of the cellular and extracellular events involved in the regulation of scleral growth and remodeling during childhood and young adulthood will provide future avenues for the treatment of myopia and its associated ocular complications.

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Age-related variations in the biomechanical properties of human sclera

Cited by 114 publications

References 52 publications

In Vivo Noninvasive Measurement of Young’s Modulus of Elasticity in Human Eyes: A Feasibility Study

In Vivo Noninvasive Measurement of Young’s Modulus of Elasticity in Human Eyes: A Feasibility Study

Experimental scleral cross-linking increases glaucoma damage in a mouse model

The dynamic sclera: Extracellular matrix remodeling in normal ocular growth and myopia development

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