Dynamic mechanical properties of human lenses

Weeber, Henk A; Eckert, Gabriele; Soergel, Fritz; Meyer, Carsten H.; Pechhold, W.; Heijde, Rob G.L. van der

doi:10.1016/j.exer.2004.10.010

Cited by 146 publications

(108 citation statements)

References 30 publications

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“…In a previous study, we measured the viscoelastic properties of entire lenses in a large age range [39]. The age correlation observed in the previous study is consistent with the findings in the current study.…”

Section: Discussionsupporting

confidence: 91%

“…Their study also showed a close-to-linear behaviour for small strains. Two other studies also demonstrated this behaviour in the crystalline lens [16,39]. In the current study, the measurements were taken in the linear elastic part of the stress-strain curve.…”

Section: Limitations Of the Test Methodssupporting

confidence: 58%

“…Therefore, our results only apply to previously frozen lenses. The effect of freezing on the measured shear modulus has been discussed extensively in a previous publication [39] and the arguments also apply to this study's results. In the previous study, pairs of porcine lenses were measured, one fresh and the other after being stored in a frozen state.…”

Section: Limitations Of the Test Methodsmentioning

confidence: 61%

“…As long as the measurement takes place in the linear viscoelastic range, the measured force is proportional to the amplitude of the applied displacement. The measurement procedure has been described previously [39], when it was used for determining the mechanical properties of the entire lens. In the current setup, a lens half was placed in a sample holder, while the load consisted of a vertical oscillation of a cylindrical probe, which was inserted into the lens at several positions across the cut lens surface (Fig.…”

Section: Testing Proceduresmentioning

confidence: 99%

“…Therefore, we used dynamic measurements, using multiple deformation rates. The measurement methods were based on dynamic measurement techniques that were also used in an earlier study on human lenses [39].…”

Section: Introductionmentioning

confidence: 99%

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Stiffness gradient in the crystalline lens

Weeber

Eckert

Pechhold

et al. 2007

Graefes Arch Clin Exp Ophthalmol

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140

147

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Background While the overall stiffness of the lens has been measured in a number of studies, the knowledge about the stiffness distribution within the lens is still limited. The purpose of this study was to determine the stiffness gradient in the human crystalline lens. A secondary purpose was to determine whether the stiffness gradient depends on age. Methods The local dynamic stiffness was measured in 10 human crystalline lenses (age range: 19 to 78 years). The lenses were stored at −70°C before being measured. The influence of freezing on the mechanical properties has been determined in a previous study. A small oscillating probe was used to measure the local dynamic shear modulus as a measure of lens stiffness. The measurements were taken in the cross-sectional plane through the lens equator. Results The local dynamic shear modulus varied with location for all tested lenses. The central stiffness of the oldest lens (78 years) was 10 4 times higher than the youngest (19 years) lens. The equatorial stiffness of the oldest lens was 10 2 times higher than the youngest lens. For the older lenses, the centre was 5.8-210 times stiffer than the periphery, as opposed to earlier results described by Fisher (1971), who found that the periphery was up to 3 times softer than the centre for lenses younger than 70-years-old. For the three youngest lenses (19 to 49 years), the periphery was 2.2-16.6 times stiffer than the centre. Conclusions The dynamic stiffness of the crystalline lens varies with location within the lens. The stiffness gradient depends on the age of the lens. The results of the 10 lenses indicate that the stiffness of both centre and periphery increase with age, but at a different rate.

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Section: Discussionsupporting

confidence: 91%

Section: Limitations Of the Test Methodssupporting

confidence: 58%

Section: Limitations Of the Test Methodsmentioning

confidence: 61%

Section: Testing Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Stiffness gradient in the crystalline lens

Weeber

Eckert

Pechhold

et al. 2007

Graefes Arch Clin Exp Ophthalmol

Self Cite

140

147

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Proper Material Properties Are Required for the Finite Element Method

Schachar¹

2006

Arch Ophthalmol

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Amphiphilic PLGA‐PEG‐PLGA triblock copolymer nanogels varying in gelation temperature and modulus for the extended and controlled release of hyaluronic acid

Osorno

Maldonado

Whitener

et al. 2019

J of Applied Polymer Sci

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Different compositional parameters of poly(D,L‐lactic‐co‐glycolic acid)‐b‐poly(ethylene glycol) triblock copolymers (PLGA‐PEG) were varied to analyze their effect on gel formation and mechanical properties. Parameters such as hydrophilic/hydrophobic ratio (PLGA/PEG ratio), lactic acid/glycolic acid ratio (LA/GA ratio), PEG molecular weight (PEG Mw), polymer solution concentration, copolymer molecular weight (Mw), and polydispersity index (PDI) were studied in this work. For copolymers with PEG Mw of 1500 Da, gelation temperature (34–37 °C) was affected by D,L‐LA/GA ratio and Mw; while modulus was affected by LA/GA ratio, Mw, and Mn. Based on the parametric study, an injectable, thermoresponsive hyaluronic acid (HA) delivery platform was designed for ocular applications. PLGA‐PEG copolymers with D,L‐LA/GA ratio of 15/1, PLGA/PEG ratio of 2/1, PEG Mw of 1500 Da, and Mw of about 6 KDa gelled at 35 °C, were optically transparent, had a modulus less than 350 Pa and were used for HA release studies. This work also demonstrates, for the first time, an extended and controlled release of HA, beyond 2 weeks, from injectable hydrogels modified with a noncovalent interacting agent, poly(L‐lysine). Smaller PLL chains slowed down the HA release kinetics, while larger PLL chains produced a release profile similar to the nonmodified hydrogels. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48678.

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Dynamic mechanical properties of human lenses

Cited by 146 publications

References 30 publications

Stiffness gradient in the crystalline lens

Stiffness gradient in the crystalline lens

Proper Material Properties Are Required for the Finite Element Method

Amphiphilic PLGA‐PEG‐PLGA triblock copolymer nanogels varying in gelation temperature and modulus for the extended and controlled release of hyaluronic acid

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