title: An analytical approach to corneal mechanics for determining practical, clinically-meaningful patient-specific tissue mechanical properties in the rehabilitation of vision.
abstract: Patient-specific biomechanical properties of the human cornea are rarely used with finite elements analysis. In order for that to be possible, a proper formulation for biomechanical properties that is based on patient-specific measurable values must be used. In this study, we propose a formula that simulates hyperelastic stress-strain curves based on non-invasive clinical measurements that can be acquired in vivo. These consist of, but are not limited to, center corneal thickness and center corneal curvature as well as corneal resistance factor and applanation diameter that are measured during non-contact tonometry. The presented formulation was demonstrated and validated through several computer simulations. First, mean values that were reported in literature were inputted into the formula to simulate a curve that represents a healthy case. This case was compared to two independent in vitro studies. Then, a sensitivity analysis was carried to identify inputs that have the most dominant effect. Finally, a finite element analysis simulating elevations in intraocular pressure was conducted; the corneal model comprised of patient-specific corneal geometry that was measured in vivo in our clinic as well as the current formulation for patient-specific corneal biomechanics. "Strong" and "weak" corneal tissue cases were simulated and deformations as well as instantaneous curvature optical maps were derived. Results for the simulated healthy curve showed good agreement with the in vitro studies. The sensitivity analysis found the corneal resistance factor and applanation diameter to have the most dominant influence. The finite element analysis of strong and weak biomechanical properties resulted in corneal deformations and instantaneous curvature optical maps that are common for healthy and pathological conditions respectively. In conclusion, the presented modeling technique can be used to assess corneal biomechanics in vivo and therefor may enhance follow-up on the effectiveness of clinical treatments, rehabilitation of vision and perhaps improve the diagnosis of pathologies that are related to corneal biomechanics.
authors.affiliation: Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, 69978, Israel.
authors.forename: Roy
authors.initials: R
authors.lastname: Asher
authors.forename: Amit
authors.initials: A
authors.lastname: Gefen
authors.forename: Elad
authors.initials: E
authors.lastname: Moisseiev
authors.forename: David
authors.initials: D
authors.lastname: Varssano
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D003315:Cornea / Q000502:physiology*; D003316:Corneal Diseases / Q000503:physiopathology / Q000534:rehabilitation*; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008954:Models, Biological; D020127:Recovery of Function; D014786:Vision Disorders / Q000503:physiopathology / Q000534:rehabilitation*