Page 226 - Computational Retinal Image Analysis

CHAPTER

Diabetic retinopathy and

maculopathy lesions 12

a
b
a
c
Bashir Al-Diri , Francesco Calivá , Piotr Chudzik , Giovanni Ometto ,
d
Maged Habib
a
School of Computer Science, University of Lincoln, Lincoln, United Kingdom
b
Department of Radiology and Biomedical Imaging, Musculoskeletal Quantitative Imaging
Research Group, University of California, San Francisco, San Francisco, CA, United States
c
Optometry and Visual Science, School of Health Sciences, University of London, London,
United Kingdom
d
Sunderland Eye Infirmary, South Shields and Sunderland City Hospitals NHS Foundation Trust,
Sunderland, United Kingdom
1 Introduction
Diabetic retinopathy (DR) is a chronic progressive sight-threatening disease of the
retinal microvasculature associated with prolonged high elevated blood sugar levels
(hyperglycemia) as well as other linked conditions such as hypertension. DR can be
asymptomatic for long periods and as the disease progresses, patients can experience
mild sight impairments. However, late stages of the disease can lead to severe sight-
threatening conditions and potential blindness, if untreated. Vision loss can occur
secondary to either leak in the center of the retina (macula)—leading to diabetic
macular edema—or due to the development of new vessels that can bleed inside
the eye. DR can manifest in forms of blurred and/or fluctuating vision, dark spots
fluctuating during saccades, empty vision areas, and reduced vision. From a clinical
perspective, DR can be classified as a nonproliferative stage (NPDR) or as a more
advanced proliferative stage (PDR). In NPDR, damages occur in the inner retinal
blood vessels, which leak of fluids onto the retina, resulting in edema and swelling
[1]. In this scenario, Frank [2] defines lesions as the major sign of retinopathy, and
clusters them as microaneurysms (MAs), hemorrhages (HMs), hard and soft exudates
(EXs), intraretinal microvascular abnormalities (IRMA), and venous beading (VB).
NPDR can be graded as mild, moderate, or severe. Mild NPDR occurs with at least
one MA. Moderate NPDR occurs with scattered retinal deep dot and blot HMs, and/
or cotton wool spots CWS (soft exudates) and IRMAs but not as extensive as severe
NPDR. The diagnosis of severe NPDR is based on the 4:2:1 rule of the ETDRS
[2a]. Furthermore, IRMA can be present in each quadrant. With respect to PDR,

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