FLOATERS AND FLASHES
What are Floaters?
Floaters are spots which can move about in the vision and which are sometimes
accompanied by flashes of light. To understand these symptoms it is necessary
to understand the basic anatomy of the eye.
Anatomy of the Eye:
In a very simplified way, the structure of the eye resembles
that of a hollow ball. The central hollow is filled with a clear jelly
called the vitreous. In the front part of this ball there is an opening,
called the pupil, leading to the outside. Lining the inside of the hollow
is a thin layer called the retina which is the part of the eye with which
a person sees. When we are teenagers the vitreous is solid like cold jello.
Floater Formation:
As part of normal changes, the vitreous gel becomes liquified.
This does not occur all at one time so there are pockets of liquified
vitreous next to solid vitreous gel with a filament-like membrane between.
When the eye moves the liquid moves easily and sloshes around, causing
the filament-like membranes to move and the movement of the membrane casts
a moving shadow on the retina, which we see as a floater. Where the membranes
are attached to the retinal surface, the movement causes a tugging, pulling
or traction on the retina. When the retina is pulled or bumped we see
the response as a flash of light. Therefore, when the eye moves we see
floaters and sometimes we also see light flashes.
If the membrane attached to the retina pulls strongly enough, it can
produce a tear or hole in the retina. When a tear forms, there may be
a small amount of bleeding, and blood particles moving around in the liquid
create floaters which are like a shower of tiny black spots.
Significance of Floaters:
Floaters are not by themselves dangerous, but are a warning that
a hole in the retina might exist or that other changes might have taken
place. Because of this, it is important for anyone who has recently developed
floaters to have a dilated eye examination, including examination of the
far edges of the retina where tears are most likely to occur. In the majority
of cases this examination will not reveal any holes. If, however, a hole
is found in the retina, it usually can be treated with either laser or
freezing application before a more serious problem, such as a retinal
detachment, develops.
Light Flashes:
These also can be associated with shrinkage of the jelly and
can occur independent of floaters. They are thought to be caused by retinal
stimulation by the jelly as it moves with eye movements and bumps the
retina, much as flashes can be caused by rubbing the eyes. Retinal hole
formation can also cause light flashes, and so the presence of this symptom
requires a careful retinal examination. Flashes can occur from other causes
as well.
Follow-up of Floaters and Flashes:
Repeat examinations are indicated if suspicious signs are found
during an eye examination or if later the patient notices either a sudden
increase in floaters and flashes or a veil blocking part of the vision.
In the latter instance especially, the doctor should be contacted immediately.
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