The intraocular fluid
(aqueous humor) is continuously secreted from the blood into
the eye, cleansing and bringing vital nourishment to the eye’s
inner structures. The fluid then exits from the eye, returning
to the blood stream. The unimpeded circulation of this intraocular
fluid is essential to good ocular health. The anterior chamber
is the fluid-filled compartment within the eye just in front
of the pupil. Viewed in profile, the anterior chamber is bounded
by the domed cornea in front and by the colored iris behind.
Where the two converge they form an angle containing the channels
which drain fluid from the eye (fig. 1).
The anterior chamber angle may vary considerably in width
and still remain open, permitting normal outflow of fluid
(fig. 2). A narrow anterior chamber angle, however, is a potentially
dangerous condition. This anatomic abnormality results if
the iris (colored tissue surrounding the pupil) is bowed forward
toward the cornea (the eye’s transparent front "window"),
narrowing the distance between the two (fig. 3).
In people having narrow anterior chamber angles, under certain
circumstances -- pupil dilation, for example -- the iris may
actually contact the adjacent cornea, closing the anterior
chamber angle and interrupting the normal outflow of fluid
from the eye. This is a serious eye emergency known as acute
angle closure. Acute angle closure is marked by a sudden and
painful elevation of the intraocular fluid pressure (IOP)
to levels endangering the health of the optic nerve and, without
prompt medical or surgical intervention, rapidly progressing
to permanent loss of vision (glaucoma) (fig. 4).
[By contrast, the much more common condition called open
angle glaucoma usually results from a very prolonged but more
limited elevation of IOP causing few if any early symptoms
before vision loss results.]
Because of its real threat to vision, once narrow anterior
chamber angles are diagnosed and the risk of angle closure
glaucoma determined, preventive treatment is advisable. A
quick and simple laser procedure (peripheral iridotomy) to
create a microscopic opening in the iris is highly effective
in markedly reducing this risk (fig. 5).
The iris opening serves as a "relief valve" which
equalizes fluid pressure behind and in front of the iris,
averting angle closure.
The laser procedure itself causes little sensation. Side
effects, if any, may include transient blurring of vision,
mild inflammation, temporary elevation of IOP and, less commonly,
minimal bleeding at the treatment site. Eye drops are used
immediately prior to treatment and for several days thereafter
to control inflammation and minimize IOP rise. The small potential
for side effects of laser treatment is far outweighed by the
serious consequence of angle closure glaucoma if narrow anterior
chamber angles are left untreated.
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