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Fluorescein
Angiography / Indocyanine Green Digital Angiography
Fluorescein
Angiography is a diagnostic procedure, which uses a special camera
to take a series of photographs of the retina, the light sensitive
tissue in the back of the eye. A special water-soluble dye (Fluorescein)
is injected into a vein in the arm. The dye travels through the
veins and into the arteries, which circulate throughout the body.
As the dye passes through the blood vessels of the retina, a special
camera flashes a blue light into the eye and takes multiple photographs
of the retina.
If the blood vessels are abnormal, the dye may leak into the retina
or stain blood vessels. Damage to the lining underneath the retina
or the appearance of abnormal new blood vessels growing beneath
the retina may also be revealed. The precise location of these abnormalities
can be determined by a careful interpretation of the fluorescein
angiogram by your physician.
Indocyanine is a green dye, which fluoresces with invisible infrared
light; it requires a special digital camera that is sensitive to these light
rays. The Indocyanine Green Angiogram is often better for studying
the deeper choroidal blood vessel layer. Certain eye disorders are
usually imaged with the fluorescein. Indocyanine is especially helpful
when there is a leakage of blood, which makes interpretation of
fluorescein studies difficult.
Both of these
tests are considered safe and serious side effects from these tests
uncommon. However, there is possibility that there may be a reaction
to the dyes.
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Optical
Coherence Tomography
Optical Coherence Tomography is a new technology, which can perform
micron resolution imaging in biological tissues. The procedure of
the OCT is similar to the ultrasound except that light is used rather
than light acoustic or radio waves. Retinal thickness is a vital
consideration in the assessment of many macular diseases. The OCT
can be particularly useful in tracking any imperfection in the retina
and optic nerve.
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Laser
Treatment
In some cases,
Laser Treatment can be done to prevent or lessen severe loss of
eyesight, if the CNV (abnormal blood vessels) is discovered early
enough. The laser beam is a high-energy light that turns to heat
when it hits the parts of the retina to be treated. This heat destroys
the CNV and stops it from growing, leaking, and bleeding. A scar forms
because of the treatment and this scar creates a permanent blind
spot in the field vision.
Vision does not usually improve after Laser Treatment and in some
cases, may even be somewhat worse. However, loss of vision following the
Laser Treatment, though immediate, is usually less severe that the eventual
loss of vision that usually occurs if the Laser Treatment is not done.
In many cases, the visual distortion will disappear after laser
treatment.
Laser Treatment only works about half the time. Since macular degeneration
is a condition that is caused by the aging process, Laser Treatment
is often only a means of temporarily preventing further loss of
vision, or lessening the amount of visual loss that usually occurs.
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Photodynamic
Therapy
This type of
laser surgery may be done in one or more sessions. The idea is to
use the laser to destroy all of the damaged areas of retina where
the blood vessels have been obstructed. When these areas are treated
with the laser, the retina is likely to stop manufacturing new blood
vessels, and those that are already present tend to become inactive
or disappear.
There are side effects of pan retinal laser photocoagulation. When
only a small amount of neovascularization is present, your doctor
may suggest careful follow-up examinations. Nevertheless, the longer
the eye remains untreated the more likely vision will be lost and
blindness will occur. The earlier severe neovascularization is discovered
and the eye is treated with laser, the more likely blindness can
be prevented. If you have developed neovascularization, your doctor
will advise you about when pan retinal laser photocoagulation should
be done.
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Transpupillary
Thermotherapy
One of the most
recent treatments for Chorodial Neovasular Membranes for patients with
age related macular degeneration is Transpupillary Thermotherapy.
With TTT treatment 19 per cent of the patients will show two
or more lines of improvement in the vision, 50 per cent will have
stable vision or improvements by one line and 25 per cent
will show decreased vision. Some patients may require more than one
treatment. Thermal energy from a special laser disrupts the abnormal
Chorodial Neovasular Membranes, keeping the overlying retinal tissue
intact.
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