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Publication Date

2008-12-18

Availability

UM campus only

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Biomedical Engineering (Engineering)

Date of Defense

2008-11-19

First Committee Member

Jean-Marie Parel - Committee Chair

Second Committee Member

Vincent Moy - Committee Member

Third Committee Member

Fabrice Manns - Committee Member

Fourth Committee Member

Fotios Andreopoulos - Committee Member

Fifth Committee Member

Weiyong Gu - Committee Member

Sixth Committee Member

Robert C. Augusteyn - Outside Committee Member

Abstract

The goal of this project was to develop techniques and instrumentation to measure the elastic properties of the lens and lens capsule in situ and their changes with age using Atomic Force Microscopy (AFM). The studies include the construction, characterization, and calibration of laboratory-based Atomic Force Microscope (AFM) to measure mechanical properties of ophthalmic tissues. Atomic Force Microscopy is a nanoscale imaging technique that has been applied to mechanical property measurement through nanoindentation. Young's modulus of elasticity is determined by monitoring the cantilever deflections when it contacts the sample. The studies also include the development of tissue preparation techniques to enable measurement of the lens elasticity using AFM. This study found that lens capsule elasticity decreases with age, outer lens cortex elasticity remains constant with age, and the inner lens cortex is stiffer than the outer lens cortex. The effect of the changing biometry and mechanical properties with age was investigated by developing a mathematical model of accommodation. These changes will be the limiting factor to accommodative amplitude. Changes in lens capsule mechanical properties will affect the maximal accommodative amplitude in older eyes.

Keywords

Atomic Force Microscopy; Mechanical Properties; Lens; Accommodation; Presbyopia

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