Analysis of images of the human retina
File(s)
Author(s)
Witt, Nicholas William
Type
Thesis
Abstract
The microvasculature is implicated in the development of cardiovascular disease, and the eye
offers a unique window through which the retinal microvasculature can be imaged and
evaluated. Retinal fundus photography allows computer aided quantitative measurements
characterising vascular geometry that are believed to relate to vascular disorder and
cardiovascular risk.
Measurement of vessel diameters from non-fluorescein images is challenging for numerous
reasons. A novel measurement technique, the Sliding Linear Regression Filter (SLRF) is
proposed to overcome deficiencies in earlier approaches, and confidence gained in its
performance by comparison with manual measurements by a skilled clinician.
Non-dimensional parameters are preferred to characterise the vascular geometry to avoid
dependence on refraction of the eye. Departure of diameter relationships from optimal
conditions at arterial bifurcations is hypothesised to indicate endothelial dysfunction and to
predict risk of atherogenesis and cardiovascular risk. Other parameters of interest include
vascular length/diameter ratios and tortuosity.
A computer based semi-automatic grading tool using the SLRF method has been developed
and applied to images from the Beaver Dam Eye Study in a prospective case-control study to
explore associations between retinal vascular geometry and incident death from ischemic
heart disease (IHD) and stroke over a 10 year period. Results were obtained from 126 IHD
and 28 stroke cases, together with 528 age and gender matched controls.
Disordered arterial bifurcation optimality was associated with death from IHD, consistent
with the underlying hypothesis. Furthermore, this association appears independent of other
recognised risk factors, suggesting that it adds additional prognostic value.
Elevated conventional arterial L/D ratio was associated with death from stroke, but this
association was not maintained after adjustment for systolic blood pressure.
An interesting but unexpected association between reduced simple tortuosity and death from
IHD was found, although this should be treated with some caution, due to eccentricities in
behaviour of this parameter.
offers a unique window through which the retinal microvasculature can be imaged and
evaluated. Retinal fundus photography allows computer aided quantitative measurements
characterising vascular geometry that are believed to relate to vascular disorder and
cardiovascular risk.
Measurement of vessel diameters from non-fluorescein images is challenging for numerous
reasons. A novel measurement technique, the Sliding Linear Regression Filter (SLRF) is
proposed to overcome deficiencies in earlier approaches, and confidence gained in its
performance by comparison with manual measurements by a skilled clinician.
Non-dimensional parameters are preferred to characterise the vascular geometry to avoid
dependence on refraction of the eye. Departure of diameter relationships from optimal
conditions at arterial bifurcations is hypothesised to indicate endothelial dysfunction and to
predict risk of atherogenesis and cardiovascular risk. Other parameters of interest include
vascular length/diameter ratios and tortuosity.
A computer based semi-automatic grading tool using the SLRF method has been developed
and applied to images from the Beaver Dam Eye Study in a prospective case-control study to
explore associations between retinal vascular geometry and incident death from ischemic
heart disease (IHD) and stroke over a 10 year period. Results were obtained from 126 IHD
and 28 stroke cases, together with 528 age and gender matched controls.
Disordered arterial bifurcation optimality was associated with death from IHD, consistent
with the underlying hypothesis. Furthermore, this association appears independent of other
recognised risk factors, suggesting that it adds additional prognostic value.
Elevated conventional arterial L/D ratio was associated with death from stroke, but this
association was not maintained after adjustment for systolic blood pressure.
An interesting but unexpected association between reduced simple tortuosity and death from
IHD was found, although this should be treated with some caution, due to eccentricities in
behaviour of this parameter.
Version
Open Access
Date Issued
2019-04
Date Awarded
2019-11
Copyright Statement
Creative Commons Attribution NonCommercial Licence
Advisor
Anil, Bharath
Thom, Simon
Sponsor
Wellcome Trust (London, England)
Grant Number
071511
Publisher Department
Bioengineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)