In vivo estimation of murine iris stiffness using finite element modeling

• Type of Material: Article
• Authors: Chanyoung Lee, Emory University; Guorong Li, Duke University; Daniel W Stamer, Duke University; Christopher Ethier, Emory University
• Language: English
• Date: 2021-01-06
• Publisher: ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2020 Elsevier Ltd. All rights reserved.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.exer.2020.108374
• Title of Journal or Parent Work: EXPERIMENTAL EYE RESEARCH
• Volume: 202
• Start Page: 108374
• End Page: 108374
• Grant/Funding Information: We are grateful for funding support from the Georgia Research Alliance and National Eye Institute (Grants R01 EY030124 and R01 EY031710).
• Keywords: OPTICAL COHERENCE TOMOGRAPHY; Life Sciences & Biomedicine; DISPERSION; Ophthalmology; MICE; DISTORTIONS; Glaucoma; Biomechanical properties; Iris; Science & Technology; DILATION; Inverse finite element modeling; OCT; GLAUCOMA; PREVENTION

Abstract

The iris plays an important role in certain types of glaucoma, including primary angle-closure glaucoma and pigmentary glaucoma. Iris mechanics are also important in influencing trabecular meshwork deformation in response to intraocular pressure changes in some animal species. Although mice are widely used to study ocular disease, including glaucoma, the in vivo biomechanical properties of the murine iris are unknown. Thus, the primary objective of this study was to estimate murine iris biomechanical stiffness. We used optical coherence tomography (OCT) images of the anterior segment of living mice (n = 13, age = 7.3 ± 3.2 [mean ± SD] months) at sequentially increasing IOP levels, observing IOP-dependent iris deformations. We then used an inverse finite element model to predict iris deformations under the same conditions, estimating iris stiffness by maximizing agreement between OCT data and numerical simulations. Our results show an in vivo murine iris stiffness of 96.1 ± 54.7 kPa (mean ± SD), which did not correlate with age but was dependent on gender. Our results further showed strong evidence of reverse pupillary block, with mean posterior chamber pressure remaining at approximately 12 mmHg even as anterior chamber pressure was set to much higher levels. Our approach to monitoring iris stiffness in vivo is applicable to study potential changes of iris stiffness in various pathophysiological conditions and thus has significant potential for clinical care of ocular disease involving iris biomechanics.