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Defination
The vitreous
is the transparent jelly-like substance that fills the space between the
lens of the eye (inside the pupil) and the retina lining the back of the
eye. It is the simplest tissue of the body, since it contains very few
cells, no blood vessels, and 99% of its volume is water. It is in contact
with the retina and helps to keep it in place. The vitreous does not adhere
to the retina, except in three places: all around the anterior border
of the retina; in the macula, the tiny spot in the retina which gives
us our "detail" and central vision; and at the optic nerve disc (where
the retina sends one million nerve fibers to the brain).
Normally,
the vitreous gel shows slow changes with age; it tends to lose some of
its water and, as a result, the gel may shrink and collapse. When this
happens the vitreous separates from the retina, and this is called vitreous
detachment. In most cases, a vitreous detachment causes some "floaters"
or moving spots to appear in the patient's vision but no other problems.
In other
cases, when the vitreous shrinks, it tears the retina at the same time.
The retina is as thin as tissue paper. When the retina is torn, vitreous
gel seeps through to the underside of the retina and lifts it away from
the wall of the eye. This is called retinal detachment, which leads to
blindness if unrepaired by surgery.
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Causes,
Incidence and Risk Factors
Diabetes
may also cause complications in the eye that can damage the vitreous and
retina and can lead to permanent vision loss. Proliferative diabetic retinopathy
causes tiny new blood vessels and scar tissue to grow from the retina
into the vitreous. The scar tissue can shrink and produce a retinal detachment.
This can also cause the retinal vessels to rupture and bleed into the
vitreous, preventing light and images from reaching the retina.
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Signs
& Tests
The most
serious complication is retinal detachment:
- Light
"flashes" and blurred central vision.
- The presence
of a "veil," or shadow, over part of the field of vision.
- Large
"floaters" or spots that travel across the field of vision, possibly
indicating a partial retinal detachment or of clumped vitreous collagen
fibers.
Other visual
problems such as dark spots or "blind spots" should also be investigated
by your eye doctor.
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Treatment
Vitreous
disease is often treated with any related retinal disease. For example,
in cases of a severe retinal detachment, or growth of abnormal blood vessels
into the eye caused by diabetic retinopathy or other disease, it may be
necessary to perform a vitrectomy: removal of the vitreous gel and its
replacement with an artificial substitute. Vitrectomy may also be performed
if the vitreous is clouded by blood or scar tissue. Because changes in
the vitreous are the primary cause of retinal detachment, it is clear
that ideal techniques to prevent and repair retinal detachment require
that we learn how to prevent the vitreous gel from liquefying, shrinking,
and tearing the retina in the first place.
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