and vomiting may occur, and the eye
may be red with a dilated pupil.
Congenital glaucoma is due to an ab-
normality in the drainage angles of the
eyes before birth. Glaucoma can also be
caused by eye injury or a serious eye dis-
ease such as uveitisor lens dislocation.
Applanation tonometryis used to check
for glaucoma by measuring the pressure
within the eye. An ophthalmoscopemay
show depression of the head of the
optic nerve due to the increase in pres-
sure. Visual field testing will be needed
to assess whether vision has already
been damaged, because longstanding
or severe glaucoma can result in loss of
peripheral vision (see tunnel vision).
Prompt treatment is essential to pre-
vent permanent loss of vision. Chronic
simple glaucoma can usually be con-
trolled with eye-drops (e.g. timolol) or
tablets that reduce pressure in the eye.
Treatment needs to be continued for life.
If drugs are ineffective, surgery may be
needed to unblock the drainage chan-
nel or create an artificial channel.Acute
glaucoma requires emergency drug treat-
ment, often in hospital. Surgery, usually
iridectomy, may be necessary to prevent
a further attack.
glibenclamideAn oral hypoglycaemic
drug (see hypoglycaemics, oral)used to
treat type 2 diabetes mellitus.
gliclazideAn oralhypoglycaemic drug
(see hypoglycaemics, oral) used to treat
type 2diabetes mellitusin conjunction
with dieting. Side effects are usually mild.
glioblastoma multiformeA fast-
growing and highly cancerous type of
primary brain tumour. Glioblastoma
multiforme is a type of gliomathat often
develops in the cerebrum. The cause is
unknown. Treatment may include sur-
gery, radiotherapy, and/or chemotherapy.
gliomaA type of brain tumourarising
from the supporting connective tissue,
(glial cells), in the brain. Types of
glioma include astrocytoma, glioblastoma
multiforme, ependymoma, medulloblas-
toma, and oligodendroglioma. Symptoms,
diagnosis, and treatment are as for
other types of brain tumour.
glipizideAn oral hypoglycaemic drug
(see hypoglycaemics, oral) used to treat
type 2 diabetes mellitus. Side effects areGLASSES GLIPIZIDEG
glassesOptical devices that use lenses
to correct focusing errors in the eyes to
achieve clear vision. Lenses are made of
glass or plastic, and the shape and
thickness are chosen during avision test.
Convex lenses are needed for hypermet-
ropia(longsightedness), and concave
lenses for myopia (shortsightedness).
Tinted lenses protect the eyes from sun-
light. (See also bifocal; contact lenses)
glass eyeSee eye, artificial.
glass testA test for meningitisthat
involves pressing a clear glass against a
rash. If the rash remains visible, it may
be a form of purpura, which sometimes
occurs in meningitis.glaucomaA condition in which the
pressure of the fluid in the eyeis abnor-
mally high, causing the compression
and obstruction of the small blood ves-
sels that nourish the retina. This may
result in nerve fibre destruction and
gradual loss of vision.
The most common form of glaucoma
is chronic simple (open-angle) glauco-
ma, which rarely occurs before age 40
and often causes no symptoms until
visual loss is advanced. It is caused by a
gradual blockageof the outflow of aque-
ous humourover a period of years,
causing a slow rise in pressure. The
condition tends to run in families.
In acute (closed-angle) glaucoma, there
is a sudden obstruction to the outflow
of aqueous humour from the eye and
the pressure rises suddenly. This causes
a severe, dull pain in and above the eye,
fogginess of vision, and the perception
of haloes around lights at night. NauseaGLASS TEST
Rash visible through glass