CHAPTER 20
Eye
403
Figure 20-12C.
Glaucoma.
Glaucoma
is a group of eye diseases that produce elevated
intraocular
pressure
, usually because of obstruction of the aqueous
humor outfl ow (see Figs. 19-11B and 19-12C). Glaucoma
results in damage to the optic nerve and is a major cause of
blindness. (1)
Open
-
angle
glaucoma
is the most common type.
Fragments from normal cell degeneration become deposited
within the trabecular meshwork and endothelial lining of the
canal of Schlemm and reduce the absorption of aqueous fl uid.
Intraocular pressure rises slowly over a long period of time.
Peripheral
vision
may be reduced before the patient is aware of
the loss. As the pressure rises, the optic disk becomes cupped.
(2)
Acute
angle
-
closure
glaucoma
is also common. Occlusion
of the anterior chamber angle occurs when the peripheral iris
obstructs aqueous outfl ow. Intraocular pressure can rise quickly
and reach very high levels. Patients may present with
severe
headache
and
eye
pain
,
malaise, nausea, and vomiting. Immediate
medical intervention is necessary to prevent vision loss.
C
J.Lynch
Zonular fibers
Vitreous body
Ciliary process
Canal of Schlemm
Aqueous vein
Trabecular
meshwork
Cornea
Posterior
chamber
Anterior
chamber
Anterior chamber angle
Sclera
Ciliary
muscle
Figure 20-12A.
Posterior portion of the ciliary body.
H&E,
3
34; inset
3
102
The
ciliary body
lies posterior to the root of the
iris
, anterior
to the
ora serrata
, and interior to the
sclera
(see Fig. 20-1).
The ciliary body is triangular in shape. The anterior portion is
thick and the
posterior portion
gradually becomes thinner and
ends at the ora serrata (Fig. 20-12B). The two cell layers of the
ciliary epithelium
cover the entire surface of the ciliary body.
Ciliary
muscle
Ciliary epithelium
(pars planum)
Bulbar
conjunctiva
Ciliary epithelium
(pars planum)
Ciliary epithelium
Sclera
A
Ora serrata
Ciliary epithelium
Retinal
Retinal
pigmented
pigmented
epithelium
epithelium
Bruch
membrane
Bruch
Bruch
membrane
membrane
Retina
Retina
Pigmented
Pigmented
ciliary
ciliary
epithelium
epithelium
Basement
Basement
membrane
membrane
Ciliary epithelium
S
c
le
le
ra
ra
B
Bruch
membrane
Retinal
pigmented
epithelium
Sclera
Basement
membrane
Pigmented
ciliary
epithelium
Figure 20-12B.
Ora serrata.
H&E,
3
34; inset
3
102
The
ora serrata
is a
denticulate border
(
junction
) between
the ciliary body and the retina; this is an important anatomic
landmark for the ophthalmologist. The extended
ciliary epi-
thelium
from the ciliary body is shown on the
right side
of
the picture. The anterior portion of the
retina
is shown on
the
left side
of the picture. The
pigmented ciliary epithelium
and its
basement membrane
are continuous with the
retinal
pigmented epithelium
and the
Bruch membrane
.
Interference with the normal fl
ow of aqueous humor leads
to
increased intraocular pressure
, and a serious medical
condition,
glaucoma
, may result. The most likely sites of
blockage of the fl
ow of aqueous humor are at the trabecular
meshwork and the endothelial lining of the canal of Schlemm
rather than the venous collector system.
Figure 20-12C.
Outfl
ow of aqueous humor.
Aqueous humor
is produced in the
posterior chamber
by the
epithelium that lines the
ciliary processes
of the ciliary body
(see Fig. 20-11B,C). It fl ows through the pupil from the pos-
terior chamber to the anterior chamber (
yellow arrow
), where
it is absorbed into the
trabecular meshwork
(Fig. 20-11B). The
aqueous humor then diffuses through connective tissue and epi-
thelial tissue into the
canal of Schlemm
.
Aqueous veins
connect
the canal of Schlemm to episcleral veins, where the aqueous
humor is absorbed into the body’s venous circulation.
CLINICAL CORRELATION
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