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Amblyopia
Age Related Macular Degeneration
Cataract
Eye Injuries
Glaucoma
New Zealand National Eye Bank Trust
• Diabetes is the commonest cause of blindness
and vision impairment in the age group 20 to 60 years
• Compared to the general population, people with diabetes
have about a 25-fold risk of vision impairment
• Retinopathy is present in at least one-third of persons
with diabetes
• It threatens vision, or has already destroyed sight,
in 10% of persons with diabetes |
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Diabetes damages the blood vessels which supply the retina
of the human eye. When signs of damage are detected, a person
has "Retinopathy".
The retina is a very thin and complex layer which lines
the back and inner wall of the eye, and contains the photoreceptors
cells which convert light to chemical and electrical energy
which is conveyed to the brain via other retinal cells,
the optic nerve and the visual nerve pathways to produce,
after much further processing, our sense of "vision"
or seeing things in our environment. It is likened to the
film of a camera. If the retina is damaged, especially in
its central area (the Macula), there is irretrievable loss
of sight.
The Macula with its central areas, the fovea and foveola,
contain the "cone" photoreceptors responsible
for colour and detailed vision (e.g. reading). Light is
focused on the central macula by the lenses of the eye.
The rest of the retina is principally "rod" photoreceptors
which enable us to have some vision in low light levels.
It is vital in treating diabetic retinopathy that the central
macula area is preserved.
The inner half of the retina receives its blood supply
from the central retinal artery which enters via the optic
nerve. Diabetes causes the small blood vessels within the
retina to close and/or leak blood, fats, and fluid, all
of which are toxic to the retina which causes two types
of major damage:
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The Normal Retina
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The Retina showing Diabetic Maculopathy
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Proliferative Retinopathy
Closure of small blood vessels leads to proliferation of
abnormal blood vessels which are fragile and may bleed into
the vitreous (the "jelly" of the eye which fills
the space between the retina and the lens) and may eventually
cause the retina to detach.
Maculopathy
Leakage within the macula, especially of fluid and fat (exudates),
destroys the retinal photoreceptor and "nerve"
cells, and reduces "visual acuity" i.e. ability
to see the vision test chart.
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according to severity and your Ophthalmologist (eye doctor)
may tell you about these:
| • Minimal |
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| • Mild |
No immediate threat to sight |
| • Moderate |
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| • Pre-proliferative
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Sight threatened or already
lost. |
| • Proliferative |
Usually needs
laser treatment |
| • Pre-maculopathy |
to control |
| • Maculopathy |
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| • Advanced |
Irretrievable
sight loss |
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This treatment is the only effective way of controlling
sight-threatening retinopathy. It is most effective if able
to be undertaken before retinopathy is advanced, and when
vision is threatened by signs of impending vision loss rather
than already reduced. Macula laser treatment "dries
up" the fluid and exudates – but may take several
months, and 2-3 treatments to be effective. Overall retinal
laser treatment i.e. laser burns throughout the retina,
causes the fragile abnormal blood vessels to disappear,
or never develop. Again, several treatments may be necessary
to each eye. Where treatment has to be extensive there will
be some loss of side vision and night vision.
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The Retina after Laser Treatment
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Two main types of diabetes mellitus are recognized and retinopathy
can occur in both:
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Insulin-dependent diabetes mellitus (Type 1)
– rare in Polynesians, but in some countries
about 10 per cent of diabetes. Onset usually before
age 30 but can occur at any age; Always requires daily
insulin injection treatment.
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Non insulin-dependent diabetes mellitus (Type
2) Common. Usually develops after age 30 but can
present at any age. It may be present for many years
without there being any apparent illness or vision
symptoms. It is often associated with obesity and
there may be a family history of diabetes. Treatment
is diet and exercise alone or with addition of tablets
which reduce blood glucose levels. However, some people
may also require insulin treatment.
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Who have had diabetes for many years. After 15 years,
3 out of 4 will have retinopathy. The risk increases
progressively each year from the time of diagnosis.
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Whose diabetes is poorly controlled (the standard
test for blood glucose levels, HbA1c, being consistently
8% or greater). Strict blood glucose control is the
most important factor in the prevention of both the
development and progression of retinopathy.
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With hypertension and abnormal blood fats, and pregnancy,
which can make retinopathy progress faster than usual.
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With associated kidney disease.
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Minimise the risk of retinopathy by strict control
of blood glucose
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Have treatment for abnormal blood pressure and fats
in the blood which cause additional harm to eyes if
not controlled.
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From the time diabetes is detected, at least one
eye examination should be undertaken every 2 years
– more frequently if retinopathy is present.
Remember, vision may be normal, but retinopathy could
be present
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Follow medical advice re diet, exercise, medications
for diabetes, blood pressure and abnormal blood lipids.
Do not smoke – this causes strokes, heart attacks
and poor circulation in the legs which may result
in amputation.
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People with diabetes should all be referred by their
Family Doctor for a routine retinal examination at
least every 2 years because there is no other way
of detecting retinopathy. This is done:
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By photography for those under 66 years of age with
good vision who do not to have significant cataract,
or who do not have one of the more severe grades of
retinopathy. 66 is an arbitrary age cut-off: lens
opacities, or cataract, tend to occur in older persons
preventing good photography of the retina.
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By ophthalmologist (eye doctor) for those with more
severe retinopathy, or cataract which prevents photography.
This examination requires drops to be used to enable
the doctor to see the retina well, and is usually
more frequent than 2-yearly for those with retinopathy
(possibly every 3-6 months)
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People who fail to have this examination should be
encouraged to do so, even though they feel their vision
is satisfactory. Worsening retinopathy may give no
warning such as pain or discomfort, but may be threatening
sight. Retinopathy can deteriorate rapidly during
pregnancy, in people with poor blood glucose control
and with high blood pressure.
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Identifies those whose retinopathy is deteriorating
towards higher risk of vision loss.
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Optimises the timing of laser treatment to avert
vision loss in those with vision-threatening retinopathy
but who have normal vision.
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Early detection of retinopathy identifies those at
risk of other diabetes complications and should encourage
all possible effort to improve blood glucose control.
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Early laser treatment greatly reduces the risk of
visual loss due to proliferative retinopathy, and
from macular fluid and exudates.
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Less successful outcomes from treatment occur in
those with established advanced macular or proliferative
disease where the best that can be achieved may be
to halt progression and preserve some greatly reduced
sight.
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With early detection and adequate treatment, up to
98% of severe vision loss (bilateral blindness) can
be prevented.
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Are eye checks necessary if diabetes is mild and diet
controlled?
Yes. The risk is only slightly less in diet controlled diabetes
Are eye checks necessary if diabetes control is very
good?
The risk is considerably reduced, but other factors can
influence retinopathy development
Is fluctuating vision a sign of developing retinopathy?
Yes, it can be due to retinopathy or due to fluctuating
(high) blood sugar affecting the lens of the eye. It may
be due to the onset of Presbyopia (need to wear glasses
for close work) which usually starts to occur from mid-forties
onwards.
Is there any point in putting a big effort into diabetes
control if a person with diabetes already has retinopathy?
Yes there is! There is strong evidence that progression
of retinopathy can be slowed by about 50% in many patients
with Mild or Moderate disease. However, retinopathy is not
slowed by improved blood glucose control when it is advanced,
but response to laser treatment may be better.
Pain from laser treatment – numerous concerns
Most people who have macula treatment do not experience
pain. Treatment to the peripheral retina may cause transient
pain and a dull ache for a few hours following treatment.
The ophthalmologist will take measures to reduce pain from
laser treatment.
Does laser treatment cause blindness?
In many people retinopathy is detected too late e.g. after
a bleed into the vitreous from proliferative disease or
with advanced fluid and lipid accumulation in the central
macula causing much retinal damage and established vision
loss. In such cases vision cannot be restored, but laser
treatment is used to attempt to retain some sight. In some
advanced proliferative cases, bleeding into the vitreous
may occur and/or retinal detachment and this may be associated
with laser treatment. However, such complications would
have occurred without treatment and the eye is in a better
state if some laser has been undertaken should surgery be
necessary to remove blood from inside the eye and re-attach
the retina.
How soon do the benefits of laser treatment become evident?
Laser is extremely effective in most patients treated, but
benefits may not occur for some months after it is finished.
Vision may improve for a long time as the retinopathy stablises.
After laser treatment is finished, will it need to be
repeated each year or so?
This may be necessary in some persons with macular disease
if the disease remains active and recurs in areas of the
macula not previously requiring treatment. It is seldom
necessary for proliferative disease once all the abnormal
blood vessels have gone.
Can a patient tell if diabetes is affecting their eyes?
As indicated, occasionally fluctuating vision is a clue.
However, in early retinopathy there are no symptoms, and
visual acuity is normal (unless cataract or other disease
affecting sight is present). Hence, the need for routine
retinal examinations.
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Further Information about Diabetes and Retinopathy
Diabetes New Zealand Inc Website: www.diabetes.org.nz Email: info@diabetes.org.nz
Pharmaceutical Society of New Zealand. Pamphlet on
Type 2 Diabetes available from your Pharmacy.
Time Magazine April 14, 2003. Page 63. The ABCs of
Diabetes.
Eyes on Diabetes-A Resource for Diabetic Retinopathy
www.eyesondiabetes.org.au
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