All ETDs from UAB

Advisory Committee Chair

Yuhua Zhang

Advisory Committee Members

Christine A Curcio

Cynthia Owsley

Xincheng Yao

Document Type

Thesis

Date of Award

2013

Degree Name by School

Master of Biomedical Engineering (MBE) School of Engineering

Abstract

Cone photoreceptors are one of the two types of essential light sensitive cells that initiate the visual process in the human retina. A normal database of the cone density of healthy eyes may provide an important measure for diagnosing retinal diseases that cause photoreceptor loss, for monitoring disease progression, and for evaluating treatment out-come. Recent studies revealed that the foveal pit morphology, retina thickness, retinal nerve fiber layer (RNFL) thickness, and optic nerve head structure significantly correlated with racial background. We hypothesize that the cone density may be also modified by racial background. To test this hypothesis, I used a novel instrument called adaptive op-tics scanning laser ophthalmoscope (AOSLO) to acquire high-resolution retinal images from subjects from three different races: European-American (EA), African-American (AA), and South-Asian (SA). The subjects' ages were between 19 and 29 years old. The AOSLO retinal images rendered clearly resolved cone photoreceptors, allowing for direct assessment of the cone density in the living human retina. To improve the measurement accuracy, I evaluated the inter-rater reproducibility, examined the sampling window size, and calculated the retinal magnification factor for each study subject with consideration of the effect of the eye length and the refractive error. Cone densities were measured along two orthogonal retinal strips across the foveal center, subtending 20-degree along both the nasal-temporal and the superior-inferior axes. I assessed the cone density distribution with an advanced statistical method called mixed model analysis. In all subjects, cone density reaches a peak value at the foveal center and decreases with increasing retinal eccentricity. Statistical analysis didn't find significant difference between the cone densities of the EA and AA groups. However, the mean cone density along the temporal-nasal axis of the SA group significantly differs from those of the EA and AA groups. Interestingly, the differences between the cone densities along the superior-inferior axis of the three groups are not significant. The study suggests that a normal database of the cone density can be established with the data acquired from the EA and AA.

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