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Posterior Segment Age-related Macular Degeneration
Better Monitoring of Age-related Macular Degeneration with
Preferential Hyperacuity Perimetry
a report by
Michael Stur
Medical Retina Specialist, Department of Ophthalmology, Medical University of Vienna
Worsening vision is an almost inevitable consequence of ageing. Age- areas, affects central vision. If untreated, symptoms such as blurring,
related macular degeneration (AMD) in its advanced stage is the major scotoma (holes in the visual field) and metamorphopsia rapidly worsen
cause of visual deterioration among the elderly of the industrialised until vision deteriorates to legal blindness within several weeks or
world.
1,2
Developing countries are rapidly closing the gap, and it is months. Although the prevalence of CNV is only 10–15% among
expected that in coming years the burden of AMD will dramatically patients with dry AMD, it is responsible for over 85% of blindness
increase in those countries as well.
3
Despite the recent development of resulting from this disease.
5–7
In some rare cases, a person affected
efficient therapeutic solutions, early detection of the advanced stage by CNV may find his or her world changed overnight. In a person
of AMD is still in its infancy. This article describes the benefits of a who loses vision in one eye as a result of CNV, the risk of
preferential hyperacuity perimetry (PHP) device in assisting early developing advanced AMD in the second eye is as high as 43% within
detection of advanced AMD, thereby possibly improving the outcome five years.
8
of treatment.
Choroidal Neovascularisation Cannot Be Cured,
Progression of Age-related Macular Degeneration But Treatment Can Stop Its Deterioration
AMD is a bilateral degenerative disease that affects the macula, the CNV cannot be cured, but if caught in time its progression can be
central portion of the retina. AMD occurs in two major patterns, stopped. Until recently the gold standard for treatment of CNV was
starting with the atrophic non-exudative form (dry AMD) and photodynamic therapy (PDT), which consists of intravenous injection of
eventually developing to the neovascular exudative form (wet AMD, or a photoactivating agent such as verteporfin (Visudyne, Novartis) and
choroidal neovascularisation [CNV]). The non-exudative form is activation of this agent using a laser light source. In the retina,
defined by pigmentary changes in the retinal pigment epithelium (RPE) photoactivation occludes the exposed choroidal blood vessels and
and extracellular accumulation of debris material (drusen) between blocks their proliferation for some time. In recent years, since the
choroid and RPE. At this stage, these changes have little impact on realisation that blood vessels proliferate due to the normal presence of
vision – most patients retain good visual acuity – and the disease is angiogenic agents in the retina, effective antiangiogenic strategies
mostly asymptomatic, although some patients report mild changes in have been developed. Such treatments, including intravitreal injection
visual acuity, blurring, decreased contrast sensitivity and weak of antiangiogenic factors such as bevacizumab (Avastin, Genentech)
adaptation to darkness. Prevalence of these early and intermediate and ranibizumab (Lucentis, Genentech), also block choroidal
stages of AMD is estimated at 15% among persons above 55 years of neovascularisation and stop the rapid growth of blood vessels. A
age,
4,5
increasing from 2% for those 50–59 years of age to above 30% number of studies report that with sustained treatment regimens and
for those over 75 years of age. frequent intravitreal injections vision can be partially restored.
7,9
Patients at risk are advised to take supplementary vitamins and to quit Early Detection Is a Key Factor in Therapeutic Success
smoking. However, within five years over 6% of eyes diagnosed with The efficacy of any treatment is crucially dependent on early detection
dry AMD will develop a CNV lesion.
4
CNV lesions can be classified as of the conversion event.
10
Indeed, the first Treatment of Age-related
occult or classic according to their appearance on fluorescein Macular Degeneration with Photodynamic Therapy study group (TAP)
angiography (FA). Occult lesions are more difficult to detect and and Verteporfin in Photodynamic Therapy study group (VIP) reports
develop relatively slowly. In the more aggressive classic lesion, the demonstrated that earlier detection enhanced the benefit of
Bruch’s membrane ruptures and choroidal blood vessels invade the photodynamic therapy.
11
According to the MARINA and ANCHOR
subretinal space. Usually, the CNV lesion erupts at an extrafoveal studies, smaller lesion size at baseline (i.e. earlier detection) also
location, but choroidal blood vessels rapidly proliferate towards the predicts a better treatment outcome in ranibizumab-treated
fovea. These de novo blood vessels characteristically leak, leading to
haemorrhage and inflammatory processes. A secondary complication
Michael Stur is a medical retina specialist in the
is retinal and/or RPE elevation due to the accumulation of subretinal
Department of Ophthalmology at the Medical University
and/or sub-RPE fluid, which can shift photoreceptors from their
of Vienna. He has been principal investigator in many
original position in the retina, resulting in metamorphopsia (perception
multicentre trials such as the TAP study group and the
VIP trial. Professor Stur graduated from the University
of distorted lines). In some cases the photoreceptor layer can detach of Vienna in 1977 and achieved certification as an
from the RPE layer, triggering the death of photoreceptors and leading
ophthalmologist in 1985 and habilitation in 1989.
to scotoma (loss of vision in defined areas of the visual field). These
processes cause irreversible damage that, when reaching subfoveal
© TOUCH BRIEFINGS 2008 87
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