Graduation Semester and Year

2015

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Aerospace Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Panayiotis S. Shiakolas

Abstract

Vision deterioration is a major healthcare concern. It is estimated that one in three persons develops some form of vision reducing eye disease by the age of 65 and these numbers are expected to increase. Deterioration in visual acuity is due to ocular diseases that change the shape or clarity of the cornea. Health/shape of the cornea is extremely important as it determines the refractive power of the eye.This work studies ocular surgeries from a mechanical/structural engineering perspective. It begins by discussing laser in-situ keratomileusis (LASIK) surgery and explains the role of lasers in modifying the corneal shape to improve visual acuity. Besides LASIK, this work studies a refractive surgery involving intrastromal corneal ring (ICR) implants by developing a computationally efficient finite element (FE) model for the cornea and the implant. The results of the FE analysis qualitatively agree with published clinical studies and experimental data. The effects of ICR dimensions and surgical conditions on the postoperative visual acuity are studied. The results indicate that smaller diameter and larger thickness ICRs lead to pronounced myopic rectification and that 40-75% deep corneal pockets yield stable results and smaller diameter corneal pockets lead to pronounced myopic rectification.The second part of this research studies the Descemet’s stripping automated endothelial keratoplasty (DSAEK) surgery by understanding the limitations of this procedure and the allograft delivering devices currently used to improve surgical outcomes. A FE model was developed to analyze the stress distribution generated on the allograft during popular DSAEK allograft configurations and the results were correlated with endothelial cell (EC) health. The results of the FE analysis reveal high stress region areas for forceps, taco and double coil configurations. The obtained stress distribution results were in qualitative agreement with published experimental EC loss data. The FE modeling procedures were used for the design of a novel new inserter, binocular inserter, that has the potential to improve DSAEK surgical outcomes especially in patients with shallow anterior chambers (ACs). The inserter prototype conceptual design analysis, the allograft tip shape analysis and allograft finite element analysis results indicate that the binocular inserter should improve DSAEK surgery results by: increasing inserter tip space utilization, reducing surgical and mechanical trauma, utilizing AC maintainer, improve recovery time and size of incision, protecting against incision compression pressure issues, and modulating the location and magnitude of stresses on the allograft to facilitate natural allograft unfolding especially in constrained ACs.

Disciplines

Aerospace Engineering | Engineering | Mechanical Engineering

Comments

Degree granted by The University of Texas at Arlington

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