Glaucoma is usually caused by too much fluid pressing on the nerve
at the back of the eye. There are many types of glaucoma, but on this
page glaucoma is the term given to the 'chronic open angle' or 'primary
open angle' or 'chronic simple' glaucoma.
Pseudoexfoliation and pigmentary glaucomas are both types of chronic open
angle glaucomas, and this page applies.
Glaucoma is not a single disease, but represents conditions that
occur for different reasons with the final event being optic nerve
damage and visual field loss.
Parts of the eye involved
The
eye is a round ball the size of a small tomato. It is partly
hidden behind the eyelids...
...imagine
the eye turning as shown ...
....turning
more...
...more...
...more...
.....then
imagine 'cutting' through the eye ball...
.....this
is the view used below to explain glaucoma. The
green arrow shows the flow of fluid, like water, through
the eye.
The optic nerve in glaucoma
The optic nerve is the 'electric wire' of the eye, an it takes
messages about what you see on towards the brain. In the main type
of glaucoma the optic nerve is pressed on by extra fluid in the
eye, and this may damage the sight in the eye. See photos
What happens in glaucoma
Everybody's eye produces a fluid like water in its middle chamber.
This fluid then flows around inside the eye to the front chamber,
as shown in the diagram below... the blue arrow.
Normally fluid is made in the
ciliary body and circulates to the front chamber, where it drains
through the trabecular meshwork out of the eye. enlarge
Then, from the front chamber the fluid leaves the eye by entering a
drainage meshwork, the trabecular
meshwork, like the drainpipe of a sink or bath. From this
drainage system the fluid enters the bloodstream. The trabecular
meshwork is a type of filter system.
The trabecular
meshwork is a type of filter system: fluid leaves the eye and enters the blood stream. enlarge
In the common type of glaucoma this drainage system can block. The
fluid gets trapped in the eye, and the pressure inside the eye goes
up like a tyre being blown up to much.
This pressure or fluid then presses on the nerve at the back of the
eye. If the pressure is high or continues for a long time, usually
years, the nerve at the back of the eye may become damaged, and eventually
the sight may be affected. The pressure reduces the blood flow in the tiny blood vessels in
the optic nerve.
The aqueous fluid circulates into the anterior chamber, normally leaving through the trabecular meshwork (left), but if the drain is blocked the pressure is transmitted to the optic nerve, and damages the nerve.
If the trabecular meshwork
blocks, the aqueous fluid cannot leave the eye, and the pressure
in the eye builds up like a car tyre being pumped up too much. This pressure
damages the optic nerve at the back of the eye,
pressing it in (lower diagram). enlarge
Intraocular pressure is related to the metabolic syndrome
(Nature
2010) "Metabolic syndrome and other insulin resistance-related
features, including hepatic steatosis, increased left ventricular mass,
and proteinuria, are strongly associated with IOP".
Glaucoma suspect
Often glaucoma is detected early, and it is difficult to say for certain whether a particular patient does have glaucoma or not. Such a patient is termed a 'glaucoma suspect'.
High risk patients will be offered drops to lower pressure, as below; low risk patients may be monitored in the eye clinics; very low risk patients need to be followed up and examined about every year by their optometrist.
Patients who are glaucoma suspects will be examined in the same way as glaucoma patients, and follow the 'general health' advice on this page below.
Pre-perimetric glaucoma
If you have pre-perimetric glaucoma, your ophthalmologist believes
that you are developing glaucoma or have early glaucoma. But by definition
your visual fields will be full, and your sight very good.
But if the condition was untreated, the optic nerve would become
more damaged and, the visual fields would shrink, and then the
sight reduced. So generally treatment will be needed to stop further
damage to the optic nerve. Control of pressure is important BJO17
Use your mouse to identify parts of the eye;
aqueous flow
Blood flow to your optic nerve in glaucoma
Genes and your relations
Glaucoma is much commoner as we get older but tends to run in families. Genes control
the blockage of the drain (the 'trabecular meshwork'). The relations
of patients with glaucoma should all be checked for the condition.
If you have glaucoma and you are 70y, then all the relations (mainly
children and sisters and brothers) should be checked from the age
of 50y. If you have glaucoma age 30y, then even the children related
to you should be checked (again: sons/daughters/brothers/sisters). See.
There are may genes involved Eye
2015. These may influence high tension, low tension, or all types of glaucoma. BCA 1 gene (vascular risk factors) OT 14
the pressure in the eye and TGF signalling (higher pressure) or other biochemical pathways
extracellular matrix (low tension glaucoma with a weaker optic nerve)
eye developmen
Myocillin group.
These influence the drainage of aqueous humour through the trabecular
meshwork. For instance, and abnormal protein may be produced, and
this becomes trapped in the trabecular meshwork cells, and is toxic.
Optineurin group
These influence the axons in the optic nerve in
low tension glaucoma. The retinal ganglion cells are weaker than
usual and die earlier.
Other genes
There are many other genes: some affect the optic nerve, others
affect the trabecular meshwork cells (transport across membranes.
Others are related to blood fat levels (toxic to the optic nerve).
Myopia
There be be visual field defects that may be glaucoma related AJO 2011
The sight in glaucoma
At first the sight is normal, but it if the glaucoma
is severe, the sight may get progressively worse as below.
You cannot 'feel' glaucoma, and usually would would not know there
was anything wrong in the early stages. Case
1 for students.
If the visual fields are -12md driving may become unsafe. If -20md, patients may be disabled by there loss of field, with difficult reading and occasional falls. (md= mean deviation from normal)
A common type of loss of vision in glaucoma
At first the sight is normal,
then a small area of poor vision may develop.
This can extend, affecting much of of the sight,
or nearly all the sight.
How does the doctor or optometrist know you have
glaucoma?
Glaucoma is found by an ophthalmologist or optometrist by
measuring the eye pressure (for this & other details about
your examination see)
looking into the eye at the optic nerve (the nerve can appear 'caved
in' which we call 'cupped', as though it has been
pressed on.
See photo,
and Case 1 for students
testing the field of vision:
you sit in a special machine with your head still. Lights flash,
and you are asked to press the button if you see the light. If
you cannot see the brighter lights, this shows on the computer
print out rather like the drawing of the 'castle' above. Here
is an online
website that enables you to test you own visual field.
The basic treatment for glaucoma is eye drops, and
the main drop is latanoprost (or bimatoprost or travaprost). This is a
very effective drop, although does not work in all patients. It
causes an allergy in about 1%.
The second commonest group of drops inhibit the carbonic anhydrase
enzyme. This is the chemical that produces the aqueous fluid
in the ciliary body. The main drop now is azopt.
The third is one of the beta-blocker drops such
as betaxalol or timolol. These drops switch the tap
off that makes the fluid. You generally should not use these
drops if you get asthma or breathing difficulties, and should
use an alternative drop. They may slow the heart down (If they
make you dizzy you should stop them.) or make your ankles swell.
Stents or cyclodiode laser may also help some patients, and are in use in some centres as primary treatment mainly outside the UK
In practice the maximum combination of drops that can be used
with few side effects are these 3 drops combined, such as latanoprost
at night, timolol LA morning, and azopt 2-3 times a day.
There should be a 10 minute gap between drops so one does not wash the other
out. This combination does tend to cause slightly sore eyes, which is unfortunately
unavoidable (systemic medications cause
sore eyes also).
These are tiny tubes that can be inserted into the eye, and allow the aqueous to drain out of the eye much more easily. These can be very helpul, although they may not lower the pressure as much as a trabeculectomy. The risks are less and rthe recovery time much quicker.
Cypass stent..this becoming popular in parts of the country see
Will the sight get worse?
Once the pressure reaches a satisfactory level the glaucoma should not get worse.
A satisfactory pressure if the optic nerve is healthy is 18-20mmHg, if
the nerve is slightly damaged 14-16, and if considerably damaged 10-12
would be ideal. (The pressure level needed also depends on your type of glaucoma. People
with 'low tension glaucoma' need a lower pressure, for instance.)
People who have a pressure of 14 that never rises above 14 usually notice
little progression.
Research has shown that if a pressure is 10mmHg, hardly
any eye will be further damaged from pressure, if 11mmHg, then 10% of
eyes/patients will notice a deterioration, and so on up to 20mmHg.
It is very hard for an ophthalmologist to tell which eyes
will get worse, but
eyes with healthy looking optic nerves can take a higher
pressure
anaemia, migraine, cold hands, sleep apnoea, suggest
a lower pressure is helpful
if the visual field is full, a higher pressure may be
well tolerated
younger patients with very cupped discs and visual field
missing do need very low pressures, ideally 10mmHg
people with optic disc haemorrhages are at much higher
risk
At 20mmHg most eyes will deteriorate. But in practice the
risks of treatment, such as having to use lots of drops,
and particularly that of diamox tablets or surgery, have
to be balanced against the ideal of seeking a pressure of
10 for all patients. In practice accepting a higher pressure
in a particular patient may still mean very few patients
notice much deterioration, and is the best option. Indeed,
in an elderly patient using 2 or 3 drops there may be no
safe alternative, especially if this includes latanoprost (or
bimatoprost or travaprost).
the optic nerve is examined for 'cupping' and haemorrhages enlarge (this patient is also diabetic )
Tests each visit
At each visit these results will be analysed
eye pressure...measured most visits
optic nerve appearance and cupping....measured most visits. Generally a haemorrhage indicates the eye pressure is slightly high for the eye. They take 3-6 months to disappear.
visual fields..tested about yearly (see this excellent IGA
article which shows you how to interpret your visual field
test...it also discusses how often the test should be carried
out)
This scan below shows 'suspicious' discs, the patient may have glaucoma ('glaucoma suspect': visual fields were full and pressures normal). Glaucoma is more likely to be present if the computer measures a thinner nerve fibre layers, as indicated in red (the circles surrounding the optic disc, white arrow, 0.7 cupping right and left). Ophth17 "Ganglion cell-inner plexiform layer GPA provides a new approach for evaluating glaucoma progression. It may be more useful for detecting progression in the advanced stages of glaucoma than RNFL GPA." AJO 17 OCT scans such as these are more accurate detecting progression of early glaucoma and IOHT.
Your general health in glaucoma/intraocular
hypertension
Remember
that your general health and lifestyle have a major impact
on glaucoma and your sight. BJO 12
Smoking does increase the eye pressure, and will make your glaucoma worse BJO 16. It
also increases the risk of retinal vein occlusion (which occur in glaucoma),
macular degeneration, cataracts, stroke, and heart attacks. The exact risk
is not known, but in some patients 20 cigarettes / day will
increase loss of vision by 400%. Passive smoking 20 a day
is equivalent to smoking 5 cigarettes a day, and
increase visual loss 100%. Glaucoma gets worse much quicker in smokers BJO 17. Eye 18
Metabolic syndrome is strongly related intraocular
pressure (Nature
2010OO15). This is related to (as below) lack of exercise, high blood
pressure, obesity and liver and kidney problems. Treatment of the metabolic
syndrome will help lower eye pressure 0.8mmHg..
Exerciselowers
the eye pressure, 'an hour a day (walking) will keep the doctor away',
and half an hour will help a lot. See. and see.
Any exercise will do... eg walking, swimming, gardening.
High blood pressure will be harmful as this may, together with the glaucoma, cause a retinal
vein occlusion. A blood pressure of 140 systolic or less, may be
best, and may be lower the better as long as you feel well. See But there are other
views. We now know that eye pressure and blood pressure are related; the implication of
this is that lowering blood pressure will help in the treatment of
glaucoma. So keeping your blood pressure reasonably low is an important
part of the treatment, although too much medication may cause problems.
Oily fish will
help the circulation and probably help prevent retinal vein occlusions.
Red meat (including pork/ham) increase blood pressure; they
are best replaced, at least in part, by fish, and pulses such as
lentils and beans. Nuts have some healthy fats, and may be helpful
in small amounts...but they are 'fattening' and help to put weight
on. A Mediterranean diet helps.
9 portions of vegetables
or fruit a day will also help to keep your retinal veins and macula
healthy, and prevent cataract formation...9 a day (men) 7 (women) keeps
the doctor away. BJO 16.
A
high saturated fat diet is very harmful as it will contribute
to many conditions. A balanced diet is recommended. Saturated fat comes
from full-fat diary products such as milk, cheese, many cakes and biscuits,
and red meat. Statins help (surely a benefit of a low cholesterol).
Salt will increase blood pressure.
binge drinking, eg
4 pints of beer in one day, or more that 3 glasses of wine/day, will
cause a rise in blood pressure, again contributing to all these conditions. Coffee increases PXF glaucoma.
Obesity results in high blood pressure, lack of exercise,
and indirectly will cause problems. Many obese patients suffer from
sleep apnoea....
Sleep problems. New research
links sleep
apnoea with glaucoma. Sleep problems
are very common in obesity...these are likely if you snore a lot.
Logically if you are overweight, it is important to lose weight
to help your glaucoma. So if you do snore a lot, do lose weight,
and ask your doctor if you need to be tested for sleep apnoea. 20122014Eye14
Steroid medication puts
eye pressure up. Even inhaled
nasal steroids can increase the pressure
2.5mmHg. If you use nasal steroids (eg for allergic rhinitis), ask
your doctor if you can reduce or stop them. Steroid
tablets certainly
may put
eye pressure up; ask your doctor if you can reduce the dose (Do
not reduce steroid tablets without seeking advice.).
Retinal vein occlusions:
patients with glaucoma are much more prone to retinal
vein occlusion. The risk of a vein occlusion is
reduced by control of the glaucoma, blood pressure, and
all the other general health risk factors immediately
above.
Various drugs have warnings..'do not use in glaucoma', 'check safety with your ophthalmologist' etc. These drugs include antidepressants and drugs aiding relaxation of the bladder etc helping people to pass urine.
these drugs can start an attack of 'angle closure' glaucoma in 'at risk' patients.
therefore the only people at risk are those people who do not know they are susceptible to angle closure glaucoma. However, angle closure glaucoma is generally a painful condition with a red eye, so most people will know if they are affected. So if you start the drugs and your eye feels fine then usually the drugs are safe.
If you start such drugs and you are worried, you can have your eyes checked by an optometrist 1-2 weeks after starting them.
Steroid tablets increase eye pressure. If a dose of more than 30mg prednisolone is used for more than 4 weeks, I would recommend a glaucoma check at an optometrists.
People with high myopia may have visual field defects. It is extremely difficult to tell whether glaucoma is present.
Most patients are treated (Latanoprost) to keep the pressure down. A very low pressure 12 or less is preferred, together with addressing all the other glaucoma lifestyle measures as below.
We need to find out whether lowering the eye pressure will help, but it will take years before we get any results, so in the meantime patients are treated as a precaution.
Draw a graph of your vision
This graph represents the reduction of visual field (tested with the Humphrey visual field machine) over the years. A healthy eye without glaucoma loses visual field very slowly enlarge
Ask your doctor to draw a graph of your visual field.
The healthy eye keeps good vision, although the optic nerve neurones do eventually die very slowly. If we lived 250y our optic nerve neurones may all die and we would have poor sight.
A sight impaired person has lost about 15 db of vision, although the number is very variable. If you lose central vision, your sight may be impaired at -10db; if very peripheral, may be -18db.
Someone with very poor sight has generally lost -18db or more, 25db on this graph.
An eye with glaucoma loses visual field much faster (black line) compared to a healthy eye (dashed line). enlarge
In glaucoma the pressure on the optic nerve neurones causes them to die early and the sight deteriorates more quickly.
(In normal tension glaucoma there are other factors that cause early neurone death, but the treatment is the same..to lower the pressure.)
The average patient loses sight at the rate of 1-2 db a year.
Patients visual field = black line;
healthy eye= dashed line.
As soon as treatment is started (green arrow) the rate of deterioration slows down and may be just be the same as a healthy eye enlarge.
With treatment to lower the eye pressure, then neurones die much more slowly. The treatment for most patients is eye drops, but a few patients need surgery or laser.
The drops/surgery/laser lower the pressure in the eye, so this lets more blood into the optic nerve. With the increased blood flow to the optic nerve it remains healthier, and stops or slows down deterioration of the neurones.
The rate of deterioration is variable, but the average rate is shown by the black line. A few patients deteriorate much more quickly (red line). enlarge
But there may be additional problems, for instance, the decline in vision (more neurone death) is much quicker in a few patients, and may be 12db/year.
One of the important purposes of the regular visual field test is to identify such patients who lose sight more quickly. These patients need their intervention such as surgery much earlier.
Treated glaucoma
red: pressure not low enough, sight deteriorates quickly
green: pressure lower, slower deterioration
green arrow: treatment started (eye drops, surgery, or occasionally laser) enlarge
So even with treatment some patients deteriorate (red line). They need extra treatment to slow down the deterioration more (green line).
The usual reason for this is that the eye pressure is not low enough. (Other risk factors contribute see .)
green arrow: start of treatment
blue arrow: extra treatment is added .. rate of deterioration slows down a lot enlarge
Here extra treatment is added and deterioration rate slows down.
green arrow: treatment started early, eye will keep good vision (green line).
red arrow: treatment started late, even with treatment sight will deteriorate and eye may lose more sight (red line). enlarge
If glaucoma is detected late some visual field may be missing even before treatment starts. Even with treatment, the remaining visual field may deteriorate (albeit very slowly) and some patients may become partly sighted 10 or more years later.
Here the patient's sight deteriorates to a poor level, but had it been detected early (green dashed line) this could have been avoided. However, it is not always possible to detect glaucoma early as patients do not know they have the condition.
Pressure needs to be low if patient is young, otherwise sight will be poor in 30+ years.
green arrow: treatment started
red line: deterioration at a higher presure,
green line: a lower pressure. enlarge
Younger patients need their optic nerve neurones to last longer, so they need low pressures.
By drawing these graphs using data from the visual field test, you can determine how long the visual field will last.
Tilted discs
This may cause visual field defects similar to glaucoma, but glaucoma treatment is usually not needed Eye 15. Explained here.
This graph represents the reduction of visual field (tested with the Humphrey visual field machine) over the years. A healthy eye without glaucoma loses visual field very slowly 
Patients visual field = black line; 
The rate of deterioration is variable, but the average rate is shown by the black line. A few patients deteriorate much more quickly (red line). 
green arrow: start of treatment
