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A
silent disease of the eye
By
Dr.Muditha Kulathunga, President of the College Of Ophthalmologist
of Sri Lanka
Glaucoma is a disease which can lead to permanent blindness
if not detected and treated early. In early stages it
is asymptomatic. Therefore it can be detected only at
routine screening. Cost effectiveness of such screening
needs to be assessed. However once detected and treated
adequately this disease can be almost totally controlled,
mostly with eye drops and tablets, in rare instances
by surgery.
Q: What is glaucoma?
A: In a normal eye, the contour is maintained
by keeping the pressure inside the eye globe within
a normal range. i.e. 12 – 21 mm Hg. This is maintained
by keeping the fluid that is present inside the eye
within a constant volume. In order to achieve this,
the amount of fluid entering the eye and the amount
leaving the eye is kept within a constant range. Fluid
enters the eye by the production within the eye in a
structure called cilliary body. It leaves the eye with
the waste products exuded from the tissues of the eye,
dissolved in it. When this process of fluid leaving
the eye is reduced due to blockage of the outflow channels,
fluid accumulates inside the globe causing the pressure
inside the globe to rise. When this happens the blood
flow to the nerve of the eye gets reduced due to the
fact that blood inside the vessels flow from high pressure
to low pressure area. Therefore when the pressure inside
the globe is high the blood flow to this high pressure
area is reduced. This affects the function of the optic
nerve – the nerve inside the eye. This in turn
reduces the vision of that eye.
In Sri Lanka approximately 6% of blindness is due to
glaucoma. Morbidity figures are very much higher than
this. Glaucoma is the 2nd COMMONEST CAUSE OF BLINDNESS
IN THE WORLD.
Q: How would the
patient suspect whether he or she is having Glaucoma?
A: In Glaucoma the vision Loss occurs only in
the field of vision but not the acuity of the vision.
Therefore until a considerable amount of field is lost
this fact might not be evident to the patient: see fig.
Once occurred the visual field loss in glaucoma is almost
permanent. Treatment will stop further loss of field
but not the recovery of the lost field. Therefore it’s
very important that one would detect this disease before
the permanent damage occurs.
Q: How does the
eye surgeon arrive at the diagnosis?
A: Examination of the eye using an instrument
named ophthalmoscope will reveal the condition of the
nerve of the eye. All the eye clinics in the government
health institutions are equipped with this instrument
and ophthalmic medical officers are trained to detect
this condition. Once the suspicion of glaucoma does
occur, it is needed to be confirmed by checking Intra
Ocular Pressure. If the recorded intra ocular pressure
is over 26 mm Hg it is very likely that patient is having
the condition named chronic simple glaucoma. This is
the commonest variety of glaucoma and is silent at the
onset. Therefore detection in early stages possible
only by routine screening.
Q: Once diagnosed
what should the patient do?
A: Patients should visit the eye clinic of the
nearest government hospital for follow up. Glaucoma
is essentially a disease that can be controlled like
diabetes and high blood pressure, but cannot be cured.
With adequate eye drops and / or tablets, it can be
controlled in most of the patients. At present two kinds
of drops and a tablet are provided by the government
hospital once a month. (One month’s stock is issued
free of charge) Depending on the requirement of the
patient these drugs are prescribed by the eye doctor
after checking the eye pressure. Rarely is surgery required
to control the eye pressure. If after surgery eye pressure
is controlled fully without eye drops, that situation
can be considered as a cure. If after surgery full eye
pressure control is not achieved additional drops need
to be used.
Q: How does the
patient know that adequate pressure control is achieved?
A: These patients are subjected to monitoring
with an assessment of their visual fields regularly,
usually once a year or little less.
Their intra ocular pressure should remain under 18 mm
Hg depending on the severity of the disease. These patients
require lifelong follow up of their condition in an
eye clinic. The important point that these patients
should understand is, that the eye drops or tablets
should be continued for life, and the vision will remain
more or less same. The medicine would prevent further
deterioration of vision. They need to be regular with
the medicine and should have a regular time for the
drops and / or tablets. On the day of the eye checkup
also the drops should be instilled and the tablets taken
at the usual time.
If this procedure is followed regularly they can have
near normal vision for the rest of their lives.
Q: Who are the people
who can get glaucoma?
A: If your blood relative is having glaucoma
you need to get your eyes checked regularly even before
the age of 45 years.
Once a year eyes must be screened for glaucoma. If you
have diabetes you are more prone to get glaucoma. If
you are a highly short sighted person, eyes should be
checked once a year for glaucoma. Apart from this all
the people over 45 years should get their eyes checked
for glaucoma annually.
Q: Where can they
get the screening done?
A: Eye clinic of any government hospital
From an optician who has pressure checking equipment.
At the time of spectacle check insist on eye pressure
check.
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