Glaucoma
Glaucoma
Glaucoma
Intraocular pressure
Technique
a. The patient is positioned at the slit-lamp with the forehead firmly
against the headrest.
b. Topical anaesthetic and fluorescein are instilled into the conjunctival
sac.
c. With the cobalt blue filter and the brightest beam projected obliquely at
the prism, the prism is centred in front of the apex of the cornea.
d. The dial is preset between 1 and 2 (i.e. 10–20 mmHg).
e. The prism is advanced until it just touches the apex of the cornea (A
( ).
f. Viewing is switched to the ocular of the slit-lamp.
g. A pattern of two semicircle mires will be seen, one above and one below
the horizontal midline, which represent the fluorescein-stained tear film
touching the upper and lower outer halves of the prism.
h. The dial on the tonometer is rotated to align the inner margins of the
semicircles (B
( , right).
i. The reading on the dial, multiplied by 10, gives the IOP.
Tonometry
Other types of tonometry
1. Pneumotonometers are also
based on the principle of
applanation but, instead of using a
prism, the central part of the
cornea is flattened by a jet of air;
non-portable (Fig. 1) or portable (A(
).
1. IOP. The higher the IOP, the greater the likelihood of glaucoma.
2. Age. It is more common in older individuals.
3. Race. It is significantly (perhaps four times) more common,
develops at an earlier age, and may be more difficult to control in
black individuals than in whites.
4. Family history of POAG. First-degree relatives of patients with
POAG are at increased risk.
5. Diabetes mellitus. Many studies suggest a correlation between
diabetes and POAG.
6. Myopia is associated with an increased incidence of POAG and
myopic eyes may be more susceptible to glaucomatous damage.
7. Vascular disease. A range of systemic conditions linked to
vascular compromise may be associated: systemic hypertension,
cardiovascular disease, diabetes and vasospastic conditions such
as migraine. Poor ocular perfusion may be a risk factor for
glaucoma progression.
Primary open-angle glaucoma
Genetics
Mutations at 15 loci in the human genome have so far been
identified as associated with POAG and are designated
primary open angle glaucoma-1A (GLC1A) to GLC1O.
3. Family history
• POAG or related conditions such as OHT.
• Other ocular disease in family members.
Primary open-angle glaucoma
4. Past medical history. Asking specifically about the following:
• Asthma, heart failure or block, peripheral vascular disease:
contraindications to the use of beta-blockers.
• Head injury, intracranial pathology including stroke that may
cause optic atrophy or visual field defects.
• Vasospasm: migraine and Raynaud phenomenon.
• Diabetes, systemic hypertension and cardiovascular disease
may increase the risk of POAG.
5. Current medication
• Steroids including skin cream and inhalants.
• Oral beta-blockers may lower IOP.
2. Review
• The interval to review after starting medication is set
according to the individual patient, but is usually 4–8 weeks.
• Response to the drug is assessed against the target IOP.
• If the response is satisfactory subsequent assessment is
generally set for a further 3–6 months.
Management of POAG
2. Review
• If there has been little or no response the initial drug is
withdrawn and another substituted.
• If there has been an apparently incomplete response
another drug may be added or a fixed combination
substituted.
• When two separate drugs are used the patient should be
instructed to wait five minutes before instilling the second
drug to prevent washout of the first.
• Sometimes it may be worthwhile allowing a further month
or two of treatment before altering a regimen, as response
may improve over time.
• Poor compliance or inadequate drop instillation technique
should be considered as a cause of unsatisfactory response.
• When drops are administered in the morning, it is good
practice always to enquire about whether today's dose has
been used prior to the examination.
Management of POAG
3. Perimetry. If IOP control is good and glaucomatous
damage mild or moderate with no substantial threat to
central vision, annual perimetry is generally sufficient.
1. Pupillary block
• Failure of aqueous flow
through the pupil (relative
pupillary block – A), leads to a
pressure differential between
the anterior and posterior
chambers, with resultant
anterior bowing of the iris (B
( )
and ITC (C).
• Iridotomy equalizes anterior
and posterior chamber pressure,
provided the TM remains
sufficiently functional.
Primary angle-closure
glaucoma
2. Non-pupillary block relating to
the iris • Specific anatomical
factors (anteriorly positioned
ciliary processes), and a thicker
or more anteriorly-positioned iris.
• An element of pupillary block is
invariably present, but angle-
closure is not fully relieved by
iridotomy. • Associated with a
deeper anterior chamber •
Plateau iris configuration is
characterized by a flat central iris
plane in association with normal
central anterior chamber depth.
The angle recess is very narrow, Ultrasound biomicroscopy in
with a sharp iris angulation over plateau iris configuration shows
anteriorly positioned and/or loss of the ciliary sulcus due to
orientated ciliary processes (Fig.). anterior position of the ciliary
processes
Primary angle-closure
glaucoma
3. Lens-induced angle-closure
• those cases in which a sudden change in lens volume and/or position
leads to an acute or subacute IOP rise.