Publication Date

2008-12-23

Availability

Open access

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Biomedical Engineering (Engineering)

Date of Defense

2008-11-19

First Committee Member

Fabrice Manns Ph.D. - Committee Chair

Second Committee Member

Sonia H. Yoo - Committee Member

Third Committee Member

Jorge Bohorquez - Committee Member

Fourth Committee Member

Weizhao Zhao - Committee Member

Fifth Committee Member

Jean Marie Parel - Committee Member

Sixth Committee Member

Arthur Ho, M.Optom - Outside Committee Member

Abstract

The human crystalline lens is a complex, inhomogeneous and dynamic optical element which enables the eye to adjust focus in a process known as accommodation. Age related changes in the optical and mechanical properties of the lens cause a loss in accommodative ability leading to a condition known as presbyopia. Several experimental surgical techniques are under development for the correction of presbyopia. The goal of this dissertation is to better understand the relationship between the crystalline lens shape, its non-uniform refractive index gradient and its optical power and their changes with age and accommodation. In this study direct lens power and shape measurements were acquired on isolated lenses, and on lenses mounted in a lens stretching system designed to simulate accommodation. Several lens shape and power measurement techniques were developed for this study including a Scheimpflug camera system optimized for imaging the crystalline lens. Direct measurements of lens shape and power were used to develop an age-dependent optical-mechanical model of the lens during accommodation. The study shows that the normal growth of the lens is a major contributor to the progressive loss of accommodation amplitude, independent of changes in the elastic properties of the lens. These findings suggest that accommodation can be restored by refilling the lens with a material having a uniform refractive index.

Keywords

Crystalline Lens; Accommodation; Age-dependent Optical-mechanical Model; Scheimpflug; OCT; Optics

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