Retinitis
Pigmentosa ( Night Blindness)
What is Retinitis Pigmentosa?
Retinitis
pigmentosa or RP
is the name given to
a group of eye diseases that lead to
slow damage of the photoreceptor
cells of the retina. These
photoreceptor cells are normally
responsible for capturing and
processing light rays and helping us
to see. As these cells die in RP,
patients experience progressive
vision loss.
There are 2 types
of photoreceptor cells: rod cells
and cone cells. Cone cells are
concentrated in the center of the
retina and allow us to see fine
details in the center of our vision.
They also allow us to perceive
color. Rod cells are concentrated in
the peripheral part of the retina
and provide us with side vision.
They also help us to see in dim
light. In RP, it is the rod cells
that are mainly damaged.
How does one get RP?
RP is an inherited disorder
programmed into the cells and not
caused by injury, infection or any
other external agent. Gene mutations
send faulty messages to the retinal
cells which lead to their
progressive damage.
These mutations can
be passed from parent to offspring.
So it is strongly
recommended that all members in the
family of a patient diagnosed with
RP must get their eyes checked by a
retina specialist.
Parents may have no symptoms
themselves; but may have some
children who are affected and others
who are not. Similarly, an affected
parent could have affected and
unaffected children. In some
families only the males are
affected; but females can transmit
the disease to their sons.
What are the symptoms
of RP?
RP is typically detected in
adolescents and young adults. It is
a progressive disorder. The rate of
progression and degree of visual
loss varies from patient to patient.
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What a normal person sees
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What a
patient with RP sees( Tunnel Vision)
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Initially there is reduced night
vision. Parents should specifically
note if their children have
difficulty in walking around or
playing when the lights are dim.
This is followed by a slow loss of
peripheral vision. This happens in
more advanced cases when only the
central part of the vision remains
intact leaving a
“tunnel vision”.
Most people with RP may become
“legally” blind by age 40, with a
central visual field of less than 20
degrees in diameter. But because of
the central vision being preserved
they may still be able to perform
many activities.
Eventually,
in a few advanced cases ,there may be
significant loss of functional vision ,once the optic nerve
connecting the eye to the brain gets
significantly damaged.
What tests can help?
Vision Test:
This test measures the accuracy of
central vision and provides
spectacle prescription so that the
patient can best use the remaining
vision.
Ophthalmoscopy:
A
retina specialist performs a
detailed examination of the eye
using a special magnifying glass.
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Early Retinitis Pigmentosa
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Advanced Retinitis Pigmentosa
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Visual Field Test:
This test uses a machine to measure
how much peripheral vision is left
and is an excellent tool to assess
the progress of the disease.
Fundus
Photography:
This helps to keep a permanent record of the
condition of the retina at that
moment and is useful to compare in
future tests.
How do we
treat RP?
Unfortunately till date there is NO DEFINITE cure for RP
yet.
A
nutritional therapy using vitamin
A supplements may slow progression
in many patients.
There are also several areas of
research that offer promise for
halting the disease or restoring
vision loss; but none of them have
been established or proven effective
yet. These include:
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Retinal Cell Transplantation
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Gene Therapy
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Pharmaceutical Therapy
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Nutritional Therapy
Micro-current therapy
appears to provide many patients
with a temporary subjective
improvement in their vision. It has
no side-effects and can be
self-administered by the patient at
home. (We provide a trial of this
therapy at our foundation.)
Discussing
inheritance patterns and family
planning can be useful. Occupational
therapy is important because it's
easier to adjust to declining vision
in earlier stages of vision loss.
Low Vision Aids (LVA):
Although not a treatment for RP, LVA
are useful for maintaining independence of
the patient.
Low vision
specialists available at Retina Foundation can
make personalized recommendations
for mechanical, optical, electronic,
and computer-based low vision
products.
Acknowledgements
Last Reviewed by Dr Sharang Wartikar,
14th April,2008
