Good Hope, Heartlands, and Solihull Eye Clinics

Glaucoma (adults) & chronic open angle glaucoma

David Kinshuck

Introduction

Types of glaucoma

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

a side view of the eye

The eye is a round ball the size of a small tomato. It is partly hidden behind the eyelids...

eyeball hidden by eyelids

...imagine the eye turning as shown ...

an  eye

....turning more...

an eye turning

...more...

an eye turning more

...more...

.....then imagine 'cutting' through the eye ball...

aqueous fluid draining out of the eye

.....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 taking messages to the brain

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.

aqueous fluid is made in the ciliary body

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.

aqueous fluid drains out of the eye through the trabecular meshwork

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.

aqueous draining through the anterior chamber, and draining through the trabecular meshwork and canal of schlemmif the trabecular meshwork blocks, fluid cannot drain out of the eye, the pressure goes up, and the pressure is transmitted to 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

See optic nerve circulation animation

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.

 

Use your mouse to identify parts of the eye; aqueous flow

 

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Blood flow to your optic nerve in glaucoma

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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

Genes may affect, for instance Eye 2015:

  • 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
visual fields become progressively worse if the eye pressure is not low enough

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

  1. measuring the eye pressure (for this & other details about your examination see)
  2. 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
  3. 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.
  4. examination of angles for narrow angle glaucoma

 

Treatment for chronic glaucoma in adults

Chronic glaucoma is treated with

Drops see

  • 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.
  • Drops are described in more detail.
  • 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).

 

Laser see

Laser may help a little in older patients, see. 

 

Surgery see

Trabeculectomy

Stents

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.

  • Istent  see
  • Cypass stent..this becoming popular in parts of the country see

cypass stent

 

 

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).

 

a disc haemorrhage

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

  1. eye pressure...measured most visits
  2. 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.
  3. 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)





  4. 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.

an OCT scan of optic discs: a borderline result

enlarge

 

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.
  • Metabolic syndrome is strongly related intraocular pressure (Nature 2010   OO15). 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..
  • Exercise lowers 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. 2012 2014  Eye14
  • 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.
  • Lack of vitamin D is linked to glaucoma KJO 16
  • Anxiety and depression AJO 17

Safety of various drugs in glaucoma

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.
  • they are completely safe in open angle glaucoma, the commonest type
  • all patients who have previously had narrow angle glaucoma  or chronic narrow angle glaucoma should have had iridotomies...and once there is an iridotomy the drugs are nearly 100% safe
  • 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.
  • Glucosamine increases intraocular pressure Eye 17

Glaucoma and high myopia

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

there is a naural rate or neurone death, even without glaucoma 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.

in glaucoma, the optic nerve neurones die much more quickly

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.

 

treated glaucoma deteriorates much slower 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.

 

 

most patients lose about 1db a year with glaucoma, but a few patients lose 12db a year

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.

 

 

 

 

treating glaucoma: sometimes the pressure is notlow enough and an even lower pressure is needed to slow down deterioration

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 .)

 

 

extra treatment may be needed to lower the pressure (drops or surgery) 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.

 

glaucoma needs to be detected early otherwise sight may become very poor

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.

 

younger patients need lower pressure as they will live longer

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.

 

Local optometrists with expertise in glaucoma

local optometrists