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Senior Citizen Health & Medicine
Canadians Claim Major Discovery in Fight Against Dry
Form of AMD
Age-related macular degeneration discovery is new
hope to fight leading cause of blindness in senior citizens
 Feb. 20, 2008 – Canadian scientists are claiming a
major victory in the fight against age-related macular degeneration, or
AMD, the blinding eye disease that affects millions of people and is the
leading cause of blindness in senior citizens. The international team,
led by researchers at Sainte-Justine Hospital and the Université de
Montréal, says it has identified the deficient receptor that causes the
dry form of AMD.
In the February edition of the medical journal PLoS
Medicine, the researchers explain how a deficiency of the CD36 receptor
prevents the evacuation of oxidized lipids in the eye. Those oxidized
lipids in turn accumulate and attack the layers beneath and over the
retina – thereby causing vision loss.
“Our discovery has important implications for the
development of new therapies,” explains lead researcher, Dr. Sylvain
Chemtob, who co-authored the paper with Université de Montréal
collaborator Dr. Huy Ong, a professor at the Faculty of Pharmacy, as
well as Florian Sennlaub of the Institut national de la santé et de la
recherche médicale (INSERM) in France.
Chemtob, a neonatal researcher at Sainte-Justine
Hospital and a professor at the Université de Montréal’s Department of
Pediatrics and School of Optometry, used mice and rat models to pinpoint
the scavenger receptor responsible for retinal degeneration typical of
dry AMD.
“We found that a deficiency in CD36 receptors leads to
significant and progressive age-related macular degeneration,” he says.
“CD36 deficiency leads to central vision loss – a key feature of dry
AMD.”
“This discovery brings us one step closer to
treating dry AMD, which could significantly improve the quality of life
of seniors who are most affected by this eye disease,” added co-author
Dr. Huy Ong.
“Now that we have also developed the molecules that
activate CD 36 receptor, we are working on the validation of the
efficacy of these molecules as potential therapeutic agents for dry AMD
treatment with prospect at the horizon of 2015.”
Wet and dry AMD remain an alarming cause of vision
loss in the western world, which according to the AMD Alliance
International, affect 30 million people aged 50 and over. Dry AMD is the
most pervasive of the disorders and affects 90 percent of AMD cases.
More about AMD
Age-related macular degeneration (AMD) is the
leading cause of blindness in the elderly in industrialized countries.
The macula is the central region of the retina, the tissue at the back
of the eye that detects light and converts it into electrical messages
that are sent to the brain. In the commonest form of AMD—“dry” AMD—the
light-sensitive cells in the retina (the photoreceptors) gradually die.
This degeneration might occur because of damage to the retinal pigment
epithelium (RPE). This layer of dark cells lies between the
photoreceptors and the choroid, the layer of the eye that contains blood
vessels and brings oxygen to the retina.
The RPE keeps the retina healthy by transferring
the right amount of oxygen and nutrients from the choroid to the retina
and by removing worn-out photoreceptor outer segments (the part of the
photoreceptor that actually absorbs light) in a process called
phagocytosis (engulfment and digestion).
In addition to photoreceptor
degeneration and RPE shrinkage, a layer of the choroid rich in small
blood vessels (the choriocapillaris) also shrinks in dry AMD. For
affected individuals, all these changes (which experts describe as
retinal atrophy and choroidal involution) mean that the sharp central
vision that is needed for reading and driving is destroyed, leaving only
dim, burred images or a black hole at the center of the vision.
More on dry AMD:
According to CNIB, a national charity committed to
vision health, dry AMD is the leading cause of vision loss in Canada and
affects over one million people in this country. Dry AMD occurs when the
layer of cells beneath the retina begin to age and thin, affecting the
overlying retina, which gradually dulls and blurs central vision.
Dry
AMD can also cause little or no symptoms until the disease more
advanced. As AMD gets worse, a person may see a blurred or blank spot in
the centre of vision or notice a gradual decline in their ability to see
fine print. People with dry AMD may have difficulty recognizing faces or
may need more light for reading and other tasks.
Dry AMD generally
affects both eyes, yet vision can be lost in one eye while the other eye
seems unaffected.
Links
● MedlinePlus provides links to information on
macular degeneration and an
encyclopedia page on macular degeneration (in English and Spanish)
● Pages on the US National Institutes of Health
NIH SeniorHealth site provides text and spoken information about AMD
● The
US National Eye Institute and the
UK Royal National Institute of Blind People also provide information
about AMD
● Wikipedia has pages on
the retina,
photoreceptor cells,
retinal pigment epithelium, and
choroid (note that Wikipedia is a free online encyclopedia that
anyone can edit; available in several languages)
● Learn more about the AMD Alliance
International. (http://www.amdalliance.org)
● Take the CNIB AMD Challenge to see if you are
at risk. (Click
Here)
● The original article from PLoS Medicine. (Click
Here)
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