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Jeffrey N. Weiss, M.D. , formerly Chief of Vitreoretinal
Surgery at the Joslin Diabetes Center, Faculty
member at Harvard Medical School and a Visiting
Scientist at the Massachusetts Institute of Technology,
has developed an operation to improve the eyesight
of patients with Central Retinal Vein Occlusion.
The retina of the eye is the sensory organ for
vision. If the eye is compared to a camera, the
retina would be the film where the “picture” is
formed. Proper blood circulation is needed for
the retina to function. Normally, blood flows
into the retina through the Central Retinal Artery
and leaves the eye through the Central Retinal
Vein. Both of these blood vessels enter the eye
through the optic nerve.
Central Retinal Vein Occlusion (CRVO) is caused
by a blood clot in the vein that drains the blood
from the retina of the eye. The arterial blood
enters the retina but cannot leave it due to
a blockage in the vein.
As a result, blood and fluid are backed up into
the retina, whichcauses a loss in vision. With
further damage, the blood vessels in the retina
may close leading to further visual loss with
the possible development of new abnormal blood
vessels.
These new vessels may cause a very painful type
of glaucoma and lead to blindness. Traditionally,
there has been no reliably effective treatment
to prevent the loss of vision or to improve vision
once it is lost.
Patients with high blood pressure, diabetes,
or glaucoma are at an increased risk for developing
CRVO. One researcher estimates that approximately
60,000 people develop a CRVO each year in the
United States.
A TREATMENT FOR CRVO
After a diagnosis of
CRVO has been made, many patients are advised
by their doctors that the vision may return
on its own if nothing is done to the eye. However,
spontaneous recovery of vision in CRVO is very
uncommon and when it does occur, the amount
of recovery is usually very small. The
Central Vein Occlusion Study (the largest study
of CRVO funded by the National Eye Institute
of the National Institutes of Health) showed
that only 6% of eyes with CRVO recover at
least 3 lines of vision (a 2-fold improvement)
within 1 year (i.e., if vision has dropped
to 20/200, there is only a 6% chance of it
improving to 20/100 or better). So the odds
are not in favor of recovering vision after
it is lost to CRVO.
Tissue plasminogen activator
(t-PA) is a well known "clot busting" medication
successfully used for treating heart attack
and stroke patients. Dr. Weiss has developed
the instruments to allow t-PA to be directly
injected into the retinal vein. The t-PA causes
the clot to dissolve, which helps blood flow
through the Central Retinal Vein. The operation
is performed on an outpatient basis and takes
approximately one hour. Furthermore, the
procedure is very similar to a standard vitrectomy,
which has been employed by retinal surgeons
for over 30 years to treat eye diseases that
are much less severe than CRVO.
WHAT ARE THE RESULTS?
After
a CRVO has been diagnosed, many
patients are advised by their doctors
that the vision may return on its
own if nothing is done to the eye.
However, spontaneous recovery of
vision in CRVO is very uncommon
and when it does occur, the amount
of recovery is usually very small.
The Central Vein Occlusion Study
(the largest study of CRVO funded
by the National Eye Institute of
the National Institutes of Health)
showed that only 6% of eyes
with CRVO recover at least 3 lines
of vision (a
2-fold improvement) within 1 year
(i.e., if vision has dropped to
20/200, there is only a 6% chance
of it improving to 20/100 or better).
So the odds are not in favor of
recovering vision after it is lost
to CRVO.
However, the amount and rate
of visual recovery in CRVO following our procedure
is much higher than what occurs without treatment.
To date, 90 patients with CRVO have undergone
this procedure as part of our clinical study
approved by the Institutional Review Board (which
is monitored by the Food and Drug Administration).
Of the 61 cases with at least 4 months of
follow-up data, 30 (49%) have recovered at least
3 lines of visual acuity within the first 4 months
following surgery (a 2-fold improvement), while 15 (25%)
have recovered at least 6 lines (a 4-fold improvement;
from 20/200 to 20/50, for example)!
Some of the more remarkable
results include: 1) Recovery of vision from 20/400
(legally blind) to 20/40 (usual legal limit
for driving an automobile) within 2 months following the surgical procedure,
and 20/20 vision 4 months later;
2) an improvement in vision from 20/60
to 20/25 (4
lines) within 2 months following the procedure;
3) an improvement in vision from “count
fingers” (just
being able to discern how many fingers are
held in front of one’s face) to 20/100
within one week following
the procedure; and 4) a 8-line improvement
in vision in a patient who had a severe CRVO
for at least 4 months before
the surgery. These results are very encouraging
and shows this procedure may help recover vision
that has been lost following CRVO. We presented
our technique at the American Academy of Ophthalmology
Annual Meeting in October 2000 and presented
the most recent results at the Association
for Research in Vision and Ophthalmology (ARVO)
Annual Meeting on May 3, 2001.
While we have had very positive results
even in eyes with longstanding CRVO, the final
visual acuity achieved following this procedure
may be related to the duration of CRVO and the
preoperative visual acuity. Therefore, if you
are considering having the procedure, it is better
to decide early, before the CRVO has progressed
and caused irreversible damage to the retina.
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Table
Mounted Retractors
Weiss
Microcannulation System
