ABSTRACT
Purpose: To report age?related variations in corneal stress–strain index (SSI) in healthy Indians. Methods: It was a retrospective study where healthy Indian individuals aged between 11 and 70 years who had undergone corneal biomechanics assessment using Corvis ST between January 2017 and December 2021 were enrolled. Composite corneal biomechanical parameters and corneal SSI were abstracted from Corvis ST and compared across different age groups using one?way analysis of variance (ANOVA). Also, Pearson’s correlation was used to evaluate the association between age and SSI. Results: Nine hundred and thirty?six eyes of 936 patients with ages between 11 and 77 years with mean ± SD intraocular pressure (IOP) and pachymetry of 16.52 ± 2.10 mmHg and 541.13 ± 26.39 ?s, respectively. Composite corneal biomechanical parameters such as deformation amplitude ratio max at 1 mm (P < 0.001) and 2 mm (P < 0.001), biomechanically corrected IOP (P = 0.004), stiffness parameter at A1 (P < 0.001, Corvis biomechanical index (P < 0.018), and SSI (P < 0.001) were found to be significantly different as a function of age group. We noted a statistically significant positive association of SSI with age (P < 0.001), spherical equivalent refractive error (P < 0.001), and IOP (P < 0.001) and a significant negative association with anterior corneal astigmatism (P < 0.001) and Anterior chamber depth (ACD) (P < 0.001). Also, SSI was positively associated with SPA1 and bIOP, whereas negatively associated with integrated radius, max inverse radius, and Max Deformation amplitude (DA) ratio at 1 mm and 2 mm. Conclusion: We noted a positive association of corneal SSI with age in normal healthy Indian eyes. This information could be helpful for future corneal biomechanical research.
ABSTRACT
AIM: To study the characteristics of new corneal biomechanical parameters in different degrees of myopia and analyze the correlation of the new parameter stress-strain index(SSI).METHODS: A cross-sectional study was conducted on 366 adult patients(718 eyes)with different degrees of myopia who received treatment at the First Affiliated Hospital of Dali University from October 2021 to November 2021, aged 18-50 years, and the spherical equivalent(SE)was -0.50～-16.75D. The axial length(AL)of the eye was measured by IOL master, and the new corneal biomechanical parameters, central corneal thickness(CCT)and intraocular pressure(IOP)were measured by corneal visualization Scheimpflug technology(Corvis ST). The subjects were categorized into low myopia, moderate myopia and high myopia groups according to SE. The data were analyzed by ANOVA and Pearson correlation.RESULTS: The ratio of the thinnest corneal thickness to horizontal thickness change rate(ARTh)and SSI were statistically significant(P&#x003C;0.001), while the remaining parameters were not statistically significant(P&#x003E;0.05). SSI was positively correlated with age(r=0.102, P=0.006), SE(r=0.361, P&#x003C;0.001), IOP(r=0.175, P&#x003C;0.001), CCT(r=0.098, P=0.009), SPA1(r=0.182, P&#x003C;0.001), negatively correlated with AL(r=-0.331, P&#x003C;0.001), IR(r=-0.545, P&#x003C;0.001)and had no correlation with other corneal biomechanical parameters(P&#x003E;0.05).CONCLUSION: With the increase of myopia degree and the elongation of the axial length, the SSI value becomes smaller and the corneal hardness decreases. SSI may be a helpful corneal biomechanical indicator for future research on myopia.
ABSTRACT
Glaucoma is one of the leading causes of blindness worldwide.Various factors are related to the development and progression of glaucoma.High intraocular pressure is an important risk factor.In recent years,many studies have focused on other potential risk factors for glaucoma,such as intraocular pressure-independent factors,including vascular factors,central corneal thickness,etc.The relationship between corneal biomechanical parameters and glaucoma has been attracting more and more attentions.The corneal biomechanics measurement instruments include ocular response analyzer (ORA) and corneal visualization scheimpflug technology (Corvis-ST),which are all commonly used in clinical practice.Some studies showed that the corneas in glaucoma patients were more easily to deform.Corneal biomechanical characteristics may reflect the anatomic structure weakness of the eyeball.For example,more easily deforming of cornea results in smaller tolerance of sclera and lamina cribros to intraocular pressure,which makes the optic disc more vulnerable.This may be one of the causes of glaucomatous optic nerve damage.Corneal biomechanical parameters have a certain extent relationship with the severity of glaucoma.In order to probe into the pathogenesis of glaucoma deeply,we reviewed corneal biomechanics characteristics,application of corneal biomechanical properties measuring instruments in clinical practice and the relationships between corneal biomechanics characteristics and the development and progression of glaucoma,as well as the therapeutic effectiveness of glaucoma.