Retinal Diseases: Age-Related Macular Degeneration and Retinitis Pigmentosa
Age-related macular
degeneration (AMD) is an eye disease primarily affecting the central
vision regions in people age 60 and older. According to the Macular
Degeneration Research Fund, a case of AMD is diagnosed in the
United States every 3 minutes. Each year, 1.2 million of the estimated
12 million people with AMD will suffer severe vision loss. Patients
with AMD have dark areas in their vision caused by fluid leakage
or bleeding in the macula, the center of the retina that produces
the sharpest vision. The brain initially compensates for these
dark patches. Early cellular dysfunction or spotting in the macula
may go undetected until the disease is in advanced stages.
Retinitis pigmentosa
(RP) is the most common inherited cause of blindness in people
between the ages of 20 and 60 worldwide. Around 500,000 people
in the United States suffer some level of visual impairment from
RP, and, of those, 20,000 are totally blind. RP is a degenerative
disease of the retina that affects the photoreceptor, or rod cells,
which control a person’s ability to see in dimly lit surroundings.
Vision loss is gradual and may result in diminished or lost peripheral
vision or blindness.
Normal
Vision
A person with normal
vision has frontal and peripheral vision, as shown in the example
above. The eye can see an image by interpreting light hitting
the back light-sensing cells, the rods and cones which line the
retina. If something happens to these cells, then vision distortion
or even blindness occurs. (Eye illustration courtesy of National
Eye Institute, National Institutes of Health.)
How
RP and AMD Affect Vision
A person with retinitis
pigmentosa (RP) loses much of their peripheral vision and sees
an effect sometimes called “tunnel vision.” A person
with age-related macular degeneration (AMD) loses some vision
usually in the center of their field-of-vision.
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