Glaucoma is a "silent
killer" or like "slow poison". In most cases it begins un-noticeably and
damages the eyes without any sign or symptom till it is very late and the patient is
almost at the verge of blindness. This is the reason that awareness about glaucoma and its
treatment is important to prevent this blinding disease.What
is Glaucoma?
The contents of the eye-ball are under some pressure
(intra-ocular pressure) which maintains the shape of the eye. In certain situations this
pressure may rise and be detrimental to the functioning of the nerve of the eye (optic nerve). This is called Glaucoma.
- Normal Intraocular Pressure 11 - 21 mm Hg
Rarely, pressure may not be increased but still damage to the
optic nerve occurs because of its increased vulnerability, this is called normal tension
or low tension glaucoma.
What are the Types of Glaucoma?
There are 2 main types of glaucoma
- Open Angle Glaucoma
- Angle Closure Glaucoma
The fluid of the eye (aqueous) circulates through anterior chamber and passing through the angle exits from the eye into the Canal of Schlemn. In open angle glaucoma
the passage to the canal of Schelmn offer resistance to the flow of aqueous . In angle
closure glaucoma the angle of the chamber is narrow or gets closed preventing the drainage
of aqueous from the eye. Both the situations lead to increase in intraocular pressure.
How does it lead to blindness?
Increase in pressure in the eye leads to resistance to flow of
blood into the eye leading to damage to vulnerable parts especially the optic nerve which carries the images to the
brain. First it leads to some area of loss of visual field (the extent of surrounding
visible to any one eye). This field loss progresses gradually till the eye is completely
blind. Early field loss can be detected by test called Visual Field Charting /
Examination.
Who are the people at risk of developing Glaucoma?
Following are the risk factors for Glaucoma:
- Family history of glaucoma (especially in parents and siblings)
- Refractive errors (Myopia or Hypermetropia)
- Diabetes mellitus
- Thyroid Diseases
- Injudicious use of steroids especially steriod eye drops.
- Certain eye conditions e.g. Retinal Vein Occlusions,
Pseudo-exfoliation, Pigment Dispersion Syndrome, etc.
At what age does Glaucoma occur?
Mostly glaucoma affect people in the fifth decade of their life
or later but it can occur at any age. Glaucoma can occur even in young children and
infants (Developmental Glaucoma). Occurring before the age of 3 years it is called
Congenital Glaucoma and between the age of 3 and 30-35 years it is called Juvenile
Glaucoma. Treatment of glaucoma is more difficult in young patients and operation is
required more often.
What are the signs & symptoms?
Open angle type of glaucoma usually does not give rise to any
symptoms in early stages. In late stages patients may feel pain in eyes and discomfort,
and some individuals may notice field defects (inability to see certain areas of the field
of vision). Usually this type of glaucoma is diagnosed on examination by a eye specialist
either when he suspects it because of some risk factors or during the course during the
course of a routine examination.
Angle closure type of glaucoma can give rise to pain in the eye
and headache with vomiting, seeing colored rings (haloes) around lights and redness in the
eyes usually after coming out of a movie theatre. This type of glaucoma may occur as
sudden attacks where there is severe pain in the eye, redness, watering, vomiting and blurring
of vision.
Can Glaucoma be treated?
Glaucoma can be treated but the damage done by the
disease can not be reversed or undone. Further damage to the eye by glaucoma can
be stopped. Therefore, it is of utmost importance that the glaucoma be diagnosed and
treated early before significant damage has been done.
How is Glaucoma and its severity / damage diagnosed?
Following tests are performed to diagnosed glaucoma, measure its
severity and the extent of damage:
- Intraocular Pressure (Eye Pressure): Measured by
an instrument called Applanation Tonometer (generally accepted as standard), normally
ranges between 11 and 21 mm Hg. It may be modestly raised in open angle glaucoma and
markedly raised in angle closure glaucoma. In between the attacks of angle closure
glaucoma it may be normal. It may vary at different times of the day and this variation
can be measured by noting pressures round the clock at specified interval (Phasing /
Diurnal Variation). In low tension or normal tension glaucoma the pressure may never be
higher than normal range.
- Gonioscopy: A method to assess the angle of anterior chamber of the eye. It helps in
diagnosing the type of glaucoma or even the vulnerability of the person to have attacks of
angle closure glaucoma.
- Fundus: The retina and optic nerve of the eye
can be seen by an instrument called ophthalmoscope. The optic disc undergoes characterstic
changes in glaucoma which are noted by measuring cup : disc ratio or the C:D Ratio
which is normally 0.3 to 0.4 and almost equal in both eyes. In open angle glaucoma and
later stages of angle closure glaucoma it may be increased. This increase is usually
proportionate to the extent of damage done. However, in some normal individuals also the
C:D ratio may be increased.
- Visual Fields: Simply stated it measures the
"area of vision" of a single eye, it also measures the sensitivity of each point
in this area. Visual fields are now a days charted by instrument called Computerized
Automated Perimeter (Humphrey is generally accepted as standard). In this test
light patient is shown light targets of various size and brightness and note is made of
the area where the patient can see this. The data thus collected is analysed and compared
with data of normal population. Glaucoma gives rise to characteristic field defects which
progress in a peculiar manner. This is the definitive test to not only detect glaucoma but
also assess the severity and extent of damage. The adequacy of the treatment is best
judged by visual field charting done at regular intervals.
What is the treatment of glaucoma?
The treatment options of glaucoma includes:
- Drugs
- Laser
- Operation
The treatment is decided by many factors:
- Type of glaucoma
- Stage of glaucoma
- Damage done
- Status of the other eye
- Response to other treatment already taken
- Patient compliance or reliability about taking drugs and follow
up examination
Decision regarding what treatment and when to be used should be
left to the judgment of consulting eye surgeon.
Detected early and treated properly, glaucoma is perfectly
compatible with life long good vision. If neglected it can end in blindness.
Author - Dr. Sanjay Dhawan
Last Update -
30 June, 2007
New Delhi, India
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