Page 247 - Computational Retinal Image Analysis

CHAPTER

Drusen and macular

degeneration 13

a,b
a,b
Bryan M. Williams , Philip I. Burgess , Yalin Zheng a,b
a Department of Eye and Vision Science, University of Liverpool, Liverpool, United Kingdom
b St Paul’s Eye Unit, Royal Liverpool University Hospital, Liverpool, United Kingdom

1 Introduction

Age-related macular degeneration (AMD) is a spectrum of related diseases that have
in common the progressive decline of vision as a consequence of dysfunction of
the central retina and its underlying supporting elements in older adults [1]. The
spectrum of disease encompasses non-neovascular components (drusen and RPE
abnormalities) and neovascular lesions (choroidal neovascular membrane forma-
tion and other choroidal abnormalities). Advanced AMD refers to two entities: “dry”
geographic atrophy (GA) and “wet” neovascular changes. The histopathological and
clinical characteristics of these lesions are described below. AMD is estimated to
affect more than 196 million people worldwide by 2020. The advanced forms of the
disease adversely affect quality of life, causing loss of independence in later years.
Despite new therapies for the prevention and treatment of AMD, the prevalence is
expected to rise to 288 million by 2040, in part due to rapidly aging populations [2].
AMD is a complex disease with multiple genetic and environmental associations.
Advanced AMD is more common in Caucasians than people of African origin or
Latinos [3, 4]. Rates of late AMD reported in Asian populations are comparable to
Caucasians; approximately half of Asian patients have the polypoidal variant of the
disease [5] which is much less common in other racial groups. Strong associations
exist between development of AMD and genetic variants of the complement factor H
gene as well as other genes in the alternative complement pathway [6, 7]. Modifiable
risk factors include smoking [8] and obesity [9]. Diets high in antioxidant-rich veg-
etables and fruits are associated with a lower risk of AMD [10]; the Age Related Eye
Disease Study (AREDS) demonstrated that antioxidant and zinc supplementation
can reduce the risk of progression to advanced AMD and of vision loss [11].
The principle treatment for neovascular AMD is repeated intravitreal injections
of monoclonal antibody therapies. Results of treatment are strongly influenced by
rapid commencement of therapy. The increasing availability of cross-sectional im-
aging to community optometrists in high-resource settings is driving demand for
automated image analysis to detect neovascular lesions. While there are currently

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