UCLA

A hypothesis that the optic nerve and the optic nerve sheath pull the optic disc and its peripapillary regions is proposed and named “optic nerve tethering.” Although the optic nerve traction hypothesis seems reasonable, the empirical validation has not been conducted. Because empirical validation of the hypothesis is an essential step to develop this research field, I designed a set of four research projects for the purpose. Each project accounts for each different chapter in this dissertation. Chapter 1 introduces background to understand optic nerve traction and its empirical validation. Because this dissertation requires multidisciplinary knowledge from ophthalmology, image processing, and continuum mechanics, the reader is recommended to read through materials in this introductory chapter. In Chapter 2, a research project using scanning laser ophthalmoscopy was performed to take images on the optic disc and its peripapillary regions, while the eyes were fixing in various directions. By comparing images obtained in different eye positions, mechanical deformations were analyzed by computing two-dimensional strains. By presenting the strain values caused by eye rotation, the existence of mechanical deformations was demonstrated. Chapter 3 explains a project using optical coherence tomography angiography for visualizing retinal blood vessels in 3D space. From volume changes in retinal blood vessels, the optic disc and its peripapillary regions were found to be pulled by the optic nerve, and the result was consistent with the optic nerve tethering hypothesis. Chapter 4 introduces a magnetic resonance imaging study to analyze strains in the optic nerve resulting from eye rotation. In this project, the parameterization of optic nerve path obtained by magnetic resonance imaging was used to measure local optic nerve strains, which had never before been measured. In Chapter 5, 3D digital image correlation and finite element method was employed to study adduction eye rotation. Scleral deformations from adduction were analyzed in two different ways, which validated and elaborated the optic nerve tethering hypothesis. Chapter 6 concludes this dissertation and states open research questions for the optic nerve tethering hypothesis.