Glaucoma is a disorder characterized by damage to the optic nerve
that, if untreated, leads to progressive loss of vision. In children
it is almost always caused by increased intraocular pressure (IOP).
Glaucoma is one of the leading causes of visual loss in adults,
but is rare in children. Estimates of the incidence of primary infantile
glaucoma range from 1 in 2,500 to 1 in 22,000.
Glaucoma may be classified as primary or secondary. Primary glaucoma is caused
by an underlying disorder of aqueous fluid outflow from the eye. Secondary
glaucoma occurs due to a variety of ocular defects that lead to
Glaucoma may also be classified as open
angle or closed angle (Figure
32–1). This refers to whether or not the trabecular meshwork
is visible when viewed with a goniolens,
an instrument that allows the examiner to visualize the fluid outflow
pathways. Open angle glaucoma is much more common. In this condition,
the pressure increases due to resistance within the outflow pathways,
usually caused by microscopic alterations within the trabecular
meshwork. In closed-angle glaucoma, access to the trabecular meshwork
is blocked. This is usually caused by forward movement of the iris.
This may occur for a variety of reasons, including a mass growing behind
the iris (e.g., retinoblastoma), scarring of the pupil margin causing
fluid to build up behind the iris and push it forward (as may occur
in iritis), or in patients with very small eyes (nanophthalmos).
Fluid in the eye is produced by the ciliary body. It
flows around the iris and drains into the trabecular meshwork. Top:
In closed-angle glaucoma, the fluid cannot reach the trabecular
meshwork, usually because the iris tissue moves forward and obstructs
the flow. Bottom: In open-angle glaucoma, microscopic obstruction
is present within the trabecular meshwork itself, which impedes flow,
resulting in increased intraocular pressure.
Normal ocular pressure is maintained by a balance of fluid (aqueous
humor) production by the ciliary body and fluid outflow through
the trabecular meshwork (Figures 32–2 and 32–3A
and B). Glaucoma virtually always results from obstructed outflow,
rather than fluid overproduction. When the IOP is elevated, the
optic nerve is damaged by compression against the sclera, resulting in
loss of the ganglion cells that form the optic nerve. This initially
affects the upper and lower fibers on the lateral side of the optic
nerve, causing loss of vision in an arcuate pattern above and below
the center of vision. If untreated, progressive constriction of
the visual field occurs, ultimately affecting central vision late
in the disease. Patients may not notice the peripheral loss initially,
and therefore they may remain asymptomatic until substantial damage
Glaucoma causes increased intraocular pressure, which
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