Estimation of the Corneal Young’s ModulusIn VivoBased on a Fluid-Filled Spherical-Shell Model with Scheimpflug Imaging

Abstract

Current intraocular pressure (IOP) measurement using air puff could be erroneous without applying proper corrections. Although noncontact tonometry is not considered to be accurate, it is still popularly used by eye clinics. It is thus necessary to extract the correct information from their results. This study proposes a practical approach to correctly measure IOP in vivo. By embedding a new model-based correction to the Corvis® ST, we can extract the corneal Young's modulus from the patient data. This Young's modulus can be used to correct the IOP readings. The tests were applied to 536 right eyes of 536 healthy subjects (228 male and 308 female) between March of 2012 and April of 2016. The tests were applied to patients at the Department of Ophthalmology, National Taiwan University Hospital and the Hung-Chuo Eye Clinics. The statistical analysis showed that the value for the Young's modulus was independent of all the other parameters collected from the Corvis ST, including the corneal thickness and the intraocular pressure. Therefore, it is important to independently measure the Young's modulus instead of depending on the correlation with the other parameters. This study adds the methodology of measuring corneal stiffness in vivo for ophthalmologists' reference in diagnosis.

Glaucoma vs. Biomechanical Properties of Cornea

“…The basic mechanical parameters are Young´s modulus and Poisson´s ratio. Young´s modulus ranges from 0.054 to 0.359 MPa, Poisson´s ratio has the constant value of 0.48 [16,17]. The average value of Young´s modulus (0.207 MPa) was applied in our mechanical model proposed in [15].…”

Finite Element Modeling of an Elderly Person’s Cornea and Rigid Gas Permeable Contact Lenses for Presbyopic Patients

“…Subsequently, on the basis of the corneal pressure distribution results and average size of >64 group's corneal edge-of-arc (r = 6.432 mm, RAD = 0.423 mm) [8,9], this study simulated the contact surface of RGP lenses for individuals older than 64 years by using ANSYS HFSS ® to improve the contact stress. By comparing Figures 10 and 11, we found that the stress concentration area before using the decompression design was higher than that after using the decompression design.…”

“…In this study, the IOP value (Table 1), Young's modulus, and Poisson's ratio of the cornea was adopted from a study by Shin et al [8]. They collected IOP samples from 536 healthy individuals from 2012 to 2016, and confidence interval (CI) for each age group was 95%.…”

“…Moreover, Boston XO 2 (Bausch & Lomb Incorporated, Rochester, NY, USA) and ANSYS ® workbench 15 software were used to simulate the stress distribution between the cornea and RGP lens in the three age groups on the basis of the three edge-of-arc curvatures (R 0 , R 1 , and R 2 ) of the lens (Figure 4) and the thickness of the lens center (T e ).The FEM simulation flow is shown in Figure 5, the contact lens and corneal model after design, it can load ANSYS software to calculate the corneal stress distribution. The IOP boundary condition is citied from Shin et al [8], and the RGP lens design is shown in Figure 4.…”

“…In addition, a research team from Israel [3] reported that the resolution of these lenses is relatively poor and that the glasses easily display a halo phenomenon when worn. After extensive research, many scholars have found that as an individual's age increases, the intraocular pressure (IOP) increases [4][5][6][7][8][9][10]. This increase in IOP causes stress and discomfort in the cornea while wearing RGP contact lenses.…”