Assessment of Corneal Biomechanical Behavior Under Posterior and Anterior Pressure

Yu, Ji guo; Bao, Fang Jun; Feng, Yijun; Whitford, Charles; Ye, Ting; Yan, Huang; Wang, Qin Mei; Elsheikh, Ahmed

doi:10.3928/1081597x-20121228-05

Cited by 19 publications

(13 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The numerical model used to describe the material behaviour of the ocular tissue during loading was the hyperelastic Ogden model, utilised in a number of previous studies on soft tissue [ 43 – 45 ], and presented in Equation 2 in terms of the strain energy per unit volume, W : …”

Section: Methodsmentioning

confidence: 99%

Ex vivo testing of intact eye globes under inflation conditions to determine regional variation of mechanical stiffness

et al. 2016

Self Cite

View full text Add to dashboard Cite

BackgroundThe eye globe exhibits significant regional variation of mechanical behaviour. The aim of this present study is to develop a new experimental technique for testing intact eye globes in a form that is representative of in vivo conditions, and therefore suitable for determining the material properties of the complete outer ocular tunic.MethodsA test rig has been developed to provide closed-loop control of either applied intra-ocular pressure or resulting apical displacement; measurement of displacements across the external surface of the eye globe using high-resolution digital cameras and digital image correlation software; prevention of rigid-body motion and protection of the ocular surface from environmental drying. The method has been demonstrated on one human and one porcine eye globe, which were cyclically loaded. Finite element models based on specimen specific tomography, free from rotational symmetry, were used along with experimental pressure-displacement data in an inverse analysis process to derive the mechanical properties of tissue in different regions of the eye’s outer tunic.ResultsThe test method enabled monitoring of mechanical response to intraocular pressure variation across the surface of the eye globe. For the two eyes tested, the method showed a gradual change in the sclera’s stiffness from a maximum at the limbus to a minimum at the posterior pole, while in the cornea the stiffness was highest at the centre and lowest in the peripheral zone. Further, for both the sclera and cornea, the load–displacement behaviour did not vary significantly between loading cycles.ConclusionsThe first methodology capable of mechanically testing intact eye globes, with applied loads and boundary conditions that closely represent in vivo conditions is introduced. The method enables determination of the regional variation in mechanical behaviour across the ocular surface.

show abstract

Section: Methodsmentioning

confidence: 99%

Ex vivo testing of intact eye globes under inflation conditions to determine regional variation of mechanical stiffness

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…In addition, the cornea is modeled as isotropic material, and the formula for hyperelastic material has been used to simulate its elastic properties; therefore, the behavior of the cornea material can be presumed to follow the Ogden Hyperelastic Material model. The strain energy potential can be expressed using the following equation [14]:…”

Section: Materials Propertiesmentioning

confidence: 99%

Effects of the LASIK flap thickness on corneal biomechanical behavior: a finite element analysis

et al. 2020

View full text Add to dashboard Cite

Background: It is well known that the biomechanical properties change after LASIK refractive surgery. One reason is the impact of flap creation on the residual stroma. The results have revealed that the change is closely related with the flap thickness in several studies. However, the quantitative relationships between the distributions of displacement and stress on the corneal surface and flap thickness have not been studied. The aim of the study was to quantify evaluate the biomechanical change caused by the LASIK flap. Methods: By building a finite element model of the cornea, the displacement, the stress and the strain on the corneal surface were analyzed. Results: The results showed that the corneal flap could obviously cause the deformation of the anterior corneal surface. For example, the displacement of the corneal vertex achieved 15 μm more than that without corneal flap, when the thickness of corneal flap was 120 μm thick. This displacement was enough to cause the change of aberrations in the human eyes. In the central part of the cornea, the stress on the anterior corneal surface increased with flap thickness. But the change in the stress on the posterior corneal surface was significantly less than that on the anterior surface. In addition, the stress in the central part of the anterior corneal surface increased significantly as the intra-ocular pressure (IOP) increase. Furthermore the increase of IOP had a clearly less effect on stress distribution at the edge of the cornea. Distributions of strain on the corneal surface were similar to those of stress. Conclusions: The changes in the biomechanical properties of cornea after refractive surgery should not be ignored.

show abstract

“…Studies that focus on corneal biomechanics under IOP typically utilise inflation (bulge) testing allowing corneal deformation to be assessed as a function of pressure 17–20 . Unlike conventional mechanical testing, inflation testing measures the biomechanical properties by expanding the entire cornea through a change in pressure whilst keeping the entire tissue intact 21–27 . In some studies, digital image correlation has been combined with inflation testing to provide spatially-resolved deformation mapping via of the cornea 12,19 .…”

Section: Introductionmentioning

confidence: 99%

Line-Field Optical Coherence Tomography as a tool for In vitro characterization of corneal biomechanics under physiological pressures

Kazaili

Lawman

Geraghty

et al. 2019

Sci Rep

View full text Add to dashboard Cite

There has been a lot of interest in accurately characterising corneal biomechanical properties under intraocular pressure (IOP) to help better understand ocular pathologies that are associated with elevated IOP. This study investigates the novel use of Line-Field Optical Coherence Tomography (LF-OCT) as an elastographic tool for accurately measuring mechanical properties of porcine corneas based on volumetric deformation following varying IOPs. A custom-built LF-OCT was used to measure geometrical and corneal surface displacement changes in porcine corneas under a range of IOPs, from 0–60 mmHg. Corneal thickness, elastic properties and hysteresis were calculated as a function of pressure. In addition, the effects of hydration were explored. We found that the elastic modulus increased in a linear fashion with IOP. Corneal thickness was found to reduce with IOP, decreasing 14% from 0 to 60 mmHg. Prolonged hydration in phosphate buffered saline (PBS) was found to significantly increase the elastic modulus and corneal hysteresis. Our study demonstrates that LF-OCT can be used to accurately measure the elastic properties based on volumetric deformation following physiological pressures. Furthermore, we show that prolonged hydration in PBS has a significant effect on the measured corneal properties.

show abstract

Assessment of Corneal Biomechanical Behavior Under Posterior and Anterior Pressure

Cited by 19 publications

References 23 publications

Ex vivo testing of intact eye globes under inflation conditions to determine regional variation of mechanical stiffness

Ex vivo testing of intact eye globes under inflation conditions to determine regional variation of mechanical stiffness

Effects of the LASIK flap thickness on corneal biomechanical behavior: a finite element analysis

Line-Field Optical Coherence Tomography as a tool for In vitro characterization of corneal biomechanics under physiological pressures

Contact Info

Product

Resources

About