Decoding Eye Mechanics: A New Approach to Analysing Ocular Microstructure Data
Authors: Zhou, D., Eliasy, A., Abass, A., Markov, P., Whitford, C., Boote, C., Movchan, A., Movchan, N., Elsheikh, A.
Journal: PLoS ONE
Publication Date: April 2019
Information obtained from an eye globe of a 75 year old male donor.(a), (b) anterior and posterior parts after dissection—the red arrow marks the superior direction; (c), (d) X-ray scattering fibril orientation vector maps of anterior and posterior parts; (e) fibril density in different directions obtained at a measurement point showing four peaks in density at angles ϕ1,ϕ2,ϕ′1,ϕ′2, where ϕ′1 = ϕ1 + 180° and ϕ′2 = ϕ2 + 180°; (f) a polar plot of fibril distribution at a measurement point.
Summary:
Our eyes are incredible organs, responsible for processing visual information and allowing us to perceive the world around us. The biomechanics of the eye are largely determined by the arrangement of collagen fibrils within the ocular tissues, which are responsible for maintaining the eye's shape and supporting its functions. In our recent study, we analysed the microstructure of collagen fibrils in whole eye globes and developed a method to use this data for numerical simulations of the eye's biomechanical performance.
Using wide-angle X-ray scattering, we studied the collagen fibril density and orientation in seven healthy ex-vivo human eyes. To obtain this data, we dissected each eye into anterior and posterior sections, which were then flattened for microstructure characterisation. We then developed a method to create realistic 3D maps of the fibril density and orientation, accounting for the entire eye globe.
Our findings revealed a strong preferential orientation of fibrils in the central corneal region, with 62% of fibrils aligned within the 45° sectors surrounding the temporal-nasal and superior-inferior directions. Furthermore, we discovered that 37% of fibrils have a circumferential arrangement in the limbus, and 39% of fibrils were preferentially aligned in the meridional direction near the equator of the eye.
The X-ray scattering technique we used required dissecting and flattening the ocular tissue, which created challenges in using the resulting data for numerical simulations. To overcome these challenges, we used Zernike polynomials to mathematically describe the X-ray data and present it in a form that can be easily used for building numerical models of the ocular globe.
In conclusion, our study presents an important step forward in understanding the biomechanics of the human eye. The method we developed allows for a more accurate analysis of collagen fibril distribution data, making it possible to create numerical models that account for the regional and anisotropic variation in tissue stiffness. This research not only advances our understanding of healthy eyes but also has potential applications in studying eyes with ectasia or those that have undergone surgery.