Glaucoma

What is glaucoma?

Glaucoma is an eye condition where the nerve at the back of the eye (the optic nerve) is damaged. This can lead to loss of vision. In most cases, the damage to the optic nerve is due to an increased pressure within the eye.

There are different types of glaucoma:

• Primary open angle glaucoma (also called chronic glaucoma) is the most common type. This develops slowly so that any damage to the nerve and loss of sight is gradual. The nerve fibres at the sides of the eye are the first to be affected, causing a loss of outer (peripheral) vision, which can be hard to notice. Central vision is the last to go. Open angle glaucoma affects about two in every hundred people over the age of 40. However, this increases over the age of 70 to one person in ten.   The term 'open angle' refers to the angle between the iris and sclera which is normal, in contrast to:
• Acute angle closure glaucoma where the angle is narrowed. This is uncommon. In this condition there is a sudden increase in the pressure within one eye. The eye quickly becomes painful and red.
• Secondary glaucoma is caused by various other eye conditions which can cause a rise in the pressure within the eye.

Traumatic glaucoma - after injury, if bleeding in the eye occurred the pressure rise may occur years later.
	Uveitic glaucoma - associated with iritis.
	Pseudo Capsular Exfoliation - found more commonly in Russians, Scandinavians and Eskimos.
	Pigmentary Glaucoma - found more commonly in young men (Kruckenberg spindle increases the incidence).
	Steroid Induced Glaucoma - a result of steroid pills or drops, e.g., prednisone.
	Neo-vascular Glaucoma- found in diabetes, after occlusion of the main vein of the eye, severe ischemia.

• Congenital glaucoma (buphthalmos) is where glaucoma is present from birth.

Who gets primary open angle glaucoma?

In the UK, about 1 in 50 people over 40 have glaucoma. It is unusual in people under the age of 35. It becomes more common with increasing age. Glaucoma can affect anyone, but it is more common if you:

• have a family history of glaucoma
• have very short sight
• have diabetes
• are from African or Afro-Caribbean origin

 

What are the symptoms of primary open angle glaucoma?

At first there are usually no symptoms. There is no pain or redness in the eye. Most people with glaucoma do not notice problems until quite a bit of visual loss has occurred. This is because the first part of the vision to 'go' is the outer (peripheral) field of vision. Central vision, used to focus on an object such as when we read, is spared until relatively late in the disease. Also, although glaucoma usually affects both eyes, it may not affect them equally.
The better eye may 'fill in' for a while if the other eye starts to lose patches of visual field. Some elderly people with glaucoma put their gradual failing vision down to 'just getting old'. They might not have had their eyes checked for many years and may needlessly lose their sight. Untreated glaucoma is one of the world's leading causes of blindness. But, blindness can be prevented if glaucoma is diagnosed and treated early enough.

Who should be tested for glaucoma?

Everyone aged over 35-40 should have an eye check by an optometrist at least every five years. A check every 2-3 years is advised if you are over 50. Eye checks are particularly important if you are in any of the 'at risk' groups listed above. The eye check will detect early signs of glaucoma before any significant vision loss occurs. The eye test normally includes:

measuring the eye pressure
a look at the back of the eye with a special torch
checking the field of vision

Certain people are entitled to free eye tests through the NHS. For example, people aged 40 and over with a first-degree relative (mother, father, brother, or sister) with  glaucoma.

The eye and aqueous humour

The eye needs to keep its shape so that light rays are focussed accurately onto the retina so the bulk of the eye is filled with a jelly like substance called the vitreous humour. But, in front of the lens the eye is filled with a clear fluid called aqueous humour.
Aqueous humour is a fluid made by cells of the ciliary body. This fluid fills the front of the eye and gives a little outward pressure to maintain the shape of the eye. The fluid contains oxygen and sugars to nourish parts of the eye. The fluid drains from the eye into the bloodstream through the sieve-like trabecular meshwork. This is near the base of the iris. So, there is constant production and drainage of aqueous humour fluid.

Intra-ocular pressure (IOP)

Glaucoma is a condition in which the eye pressure, also known as intra-ocular pressure (IOP), is too high for a given eye and thus causes damage to the optic nerve of that eye. (Note: each individual has a different pressure which causes damage to the optic nerve)  Damage to the optic nerve results in progressive loss of peripheral or side vision. Central or straight ahead vision is preserved until the end of the disease (tunnel vision).  Pressure is measured in mm of Hg (mercury).  Normal pressure is between 10 - 21 mm Hg with 14 being the average. Prior to 1978 glaucoma was defined as a disease in which the pressure was above 21 mm Hg in an eye. 
Today we know that this is not correct.  Only 10-20% of the patients having an eye pressure between 21-24 mm Hg go on to develop loss of the peripheral vision or loss of side vision over a ten year period of time.  Fifty percent lose peripheral vision if their pressure is consistently between 25-27 mm Hg, and 90% lose vision if the pressure is 30 mm Hg. The natural history of patients that have non-treated glaucoma is a slow progression.  Glaucoma is usually a slow disease.
Untreated glaucoma takes an average of 15 years to progress from early damage to blindness with an IOP of 21 to 25 mmHg, 7 years with 25 to 30 mmHg, and 3 years with a pressure more than 30 mmHg.  Thus, most ophthalmologists will treat a pressure over 30 without signs of damage.
Like blood pressure the eye pressure (intra-ocular pressure) will vary from day to day and time of day, usually higher in the morning and lower in the early evening.  Therefore, it can be important to measure the pressure at different times of the day.  Patients without glaucoma may vary 4 mm Hg while patients with glaucoma tend to vary more.  This variability necessitates multiple readings at different times of the day before making any decision.  Unless the pressure is very high, one reading can be meaningless. 

What Causes the Increase in Eye Pressure?

The truth is that we are not sure.  Either we make too much fluid, have restricted drainage or the ("thermostat") control system does not maintain a proper pressure.  Treatment is directed at either decreasing production of the aqueous (the fluid in the front part of the inside of the eye) or increasing the out flow. This is analogous to your sink, to maintain a constant level of water in the sink one must control the amount of water going into the sink or increase the size of the holes in the drain. Whichever mechanism is causing the increase in pressure, treatment today is directed towards reducing pressure.  Newer thoughts suggest that blood flow to the nerve may be as important as pressure.  Also, newer drugs may provide neuro-protection (slow down the death process).  The only thing that has shown to slow the progression of glaucoma is control of eye pressure.

What happens in primary open angle glaucoma?

In primary open angle glaucoma (just called 'glaucoma' from now on) there is a partial blockage within the trabecular meshwork. This restricts the drainage of aqueous humour. The reason why the trabecular meshwork becomes blocked and does not drain well is not fully understood. The pressure of the aqueous humour builds up if the drainage is faulty. But, this also increases the pressure on the back of the eye. In primary open angle glaucoma there is damage to the optic nerve (the nerve going from the eye to the brain). It is usually caused by an increase in pressure within the eye. Treatment to reduce eye pressure can prevent, or delay, glaucoma from getting worse. All adults over 35-40 should have regular eye checks to detect early glaucoma.

The increased pressure in the eye can damage the optic nerve (the main nerve of sight) and the nerve fibres running towards it from the retina. The retina contains the 'seeing' cells at the back of the eye. The damaged parts of the nerve and retina lead to permanent patches of vision loss. In some cases this can eventually lead to total blindness.

Is Glaucoma Always Due to High Pressure in the Eye?

Glaucoma means that part of the optic nerve is damaged, usually caused by increased eye pressure. But, factors such as a poor blood supply may make the optic nerve sensitive even to modest pressure. About 1 in 5 people with glaucoma have eye pressures in the normal range. This condition is known as normal or low tension glaucoma and is the most dangerous type of glaucoma in patients who do not have routine eye examinations.  There are few signs or symptoms for the patient or doctor to determine the presence of the condition.  It is often first suspected if one or both of the nerves look unusual.  Glaucomatous appearing nerves or nerves that appear differently in each eye must be carefully watched to make sure that this uncommon disease is not present. Watching includes observation of the nerve, measurement of pressure, and repeated peripheral field testing (visual fields). Glaucomatous appearing nerves may be normal for a given individual.  Change over time demonstrates the presence of glaucoma. In contrast, some people have an increased eye pressure with no ill effect to the optic nerve. However, as a rule, if your eye pressure is high you have a greater risk of developing glaucoma and visual loss.

Do the Drops Taken for Glaucoma Cure Glaucoma?

No.  Glaucoma is similar to high blood pressure.  The drops control the pressure.  Stop the drops and the pressure re-occurs.   It is important to continue the glaucoma eye drops for another reason.  Many believe that variability of pressure is more dangerous than if constantly high.  One must be committed to a life long treatment.  Laser treatment can eliminate the need for drops for some. Laser treatment is effective in 80% of the patients with glaucoma but wears off in about half in 5 years.  It can be repeated.  Surgery, which is successful, is reserved for the few in which either the drops or laser do not effectively control the pressure.  Laser and surgery can also be used in the non-compliant patient.
The tough part in the treatment of glaucoma is often to get the patient to use the drops consistently even though they have no visual disturbance- they see fine.  The drops can have side effects, which makes it even harder for the patient to continually take their drops. The drops prevent further damage, they do not restore vision already lost.  If you are bothered by the drops, do not stop taking the drops, speak to your doctor.

If I Have Normal Pressure Can I Be Assured That I Don't Have Glaucoma?

No. One third of the people who have glaucoma will have a normal eye pressure at the time of their examination.  Thus, eye pressure is not the only determinate for glaucoma but a risk factor.  Other risk factors include: age, family history of glaucoma, corneal thickness, myopia, being Afro-Caribbean, having diabetes, hypertension, or other vascular disease, e.g., migraine.  If the risk factors are too great, a patient may be treated even though the disease is not proven to be present (risk against benefit). The goal of treatment is to lower the pressure so that the pressure will not cause further damage. Thus, the treatment will not make you see better nor feel better.  The target pressure varies from patient to patient depending on the entering pressure, current damage, and/or risk factors.

I Have Heard There are Two Types of Glaucoma?

Actually there are many types of glaucoma but two major categories.  One in which the pressure increases insidiously over time and is moderately high.  This type is known as chronic or primary open angle glaucoma.  The higher pressure results from an inaccurate control system like the thermostat of your house being set to high.  Another analogy would be that too much water is coming out of a faucet vs. being drained. This increased pressure is painless and asymptomatic until the late stages, which, makes it dangerous.  Open angle glaucoma is diagnosed by pressure, risk factors, appearance of the optic nerve, and results of the visual fields test. Approximately one percent of the population have this form of glaucoma, making it the most common form of glaucoma. It occurs mainly in patients over 50. The danger of this disease is its silence. Generally, there is no pain associated with glaucoma.  By the time the vision is impaired, the damage is irreversible.

The second category is the narrow angle glaucoma.  In this condition, the eye is anatomically small causing the iris (coloured part of your eye) to bow forward. Before an attack the drainage is normal and pressure is normal. With age the angle or space between the cornea narrows. During an attack, incorrect, positioning of the iris causes the drainage system to become blocked. Closure is analogous to dropping a plug into the drain of a sink. The result - a rapid increase in pressure.  The pressure may rise from normal mid-teens to 40-70.  The eye becomes red, painful, with blurred vision or halos around lights. Often the pupil is dilated.  Nausea and headache may accompany the increase in pressure. Angle-closure glaucoma affects nearly half a million people in the United States. There is a tendency for this disease to be inherited. It is more common in people of Asian descent and people who are far-sighted.
 
This is an ocular emergency if not taken care of immediately. Severe permanent loss of vision may occur.  Fortunately, the predisposition to this type of glaucoma is easily detected during a comprehensive eye exam.  If the chances of closure in the future are significant then a laser is used to prophylaxically create another exit via the iris, like the overflow drain in your sink.  This laser treatment is simple and painless without a true recovery time.  If the angle is known to be dangerously narrow one should avoid medications that cause dilation of the pupil and may lead to an attack of glaucoma. These include anti-depressants, cold medications, antihistamines, and some medications to treat nausea. The labels of these medications usually state "do not take if you have glaucoma". Unfortunately, the patients with un-diagnosed narrow angle glaucoma are the ones at risk if they use these medications. Acute glaucoma attacks are not always full blown. Sometimes patients have numerous minor attacks. The patient might experience slight blurring of vision and/or haloes of light, with or without pain or redness.
Once the laser is performed this type of glaucoma is cured.

What Happens if I Have Glaucoma and Exercise?

Exercise seems to lower IOP and therefore decreases the risk of glaucomatous damage.  There are two exceptions: standing on ones head which increases blood flow to the head, also, increases pressure within the eye; and secondly, pigmentary glaucoma is also aggravated by physical exercise.

Will I Go Blind from Glaucoma?

If you have routine examinations and you develop glaucoma, the chances of serious vision loss from glaucoma are very remote.  However, late detection or non-compliance may result in vision loss.  One may think of glaucoma being analogous to a house on the beach.  If a house is in good shape and is hit by a series of storms, then the house will survive the storms with little damage (high eye pressure with a healthy nerve). However, if the foundation of the house has been damaged by previous storms there is a significant chance that the house will either be further damaged or swept away by the storm (a damaged nerve can not take the excess pressure from glaucoma).  Thus, the key to preserving vision is early detection with aggressive treatment.  The chronic, progressive nature of the disease makes it difficult for the patient to faithfully take their medication - the key to preserving vision.
 

What Tests Show Damage?

Visual fields tests measure side or peripheral vision.  Glaucoma causes loss of peripheral or side vision before central vision.  It is not until late into the disease is that central or visual acuity is effected.  The problem is that defects in visual fields do not show up until glaucoma is relatively advanced (over 50% of the nerve fibres must be lost before visual fields changes).  Once visual fields changes are noted it is very sensitive to progression.  Even with perfect control of eye pressure, a very, few patients will continue to lose fields.  This occurs only in very advanced glaucoma.  Previously, the best method for monitoring early glaucoma was careful evaluation of the optic nerve.  As long as the nerve doesn't change, there is no progression.  Newer, tests use laser scanning (HRII) to create a three dimensional picture of the optic nerve. The scanning lasers are accurate and quantitative than the doctor just observing the nerve. These tests may replace visual field testing in detecting early glaucoma in the future.  Late glaucoma is best followed with visual fields testing.

Can I Monitor My Own Eye Pressure (IOP) Like Diabetic Patients Monitor Their Blood Sugar?

Yes, with Proview™ Eye Pressure Monitor, a new easy to use "at home" device for measuring pressure (IOP) of the eyes. This tonometer (instrument that measures eye pressure) measures eye pressure "off of the cornea" and "out of the office".
Proview™ is sold as a complete eye pressure monitoring kit. The patient creates a logbook of their eye pressure, which will allow your doctor to more accurately monitor your glaucoma and/or the impact of your current treatment.
This device might improve  treatment of glaucoma especially in those patients showing progression despite what appears to be adequate control, large fluctuations in IOP, pigmentary glaucoma, and/or Posner Shlossman syndrome. 
Details can be found at : www.bausch.com/en_US/ecp/pharma/product/proview.aspx

What Are The Results of the Ocular Hypertensive Study and What Do They Mean to Me?

This study investigated the effect of treating patients who had elevated pressure without any evidence of damage to the nerve or an abnormal visual field.  These patients have been called ocular hypertensives or glaucoma suspects.  Until this study no one knew the natural history of patients with elevated pressure without damage. Half the subjects were treated with eye drops while the other half were watched.  Eye drops reduced the development of glaucoma by over 50% in a study of 1636 people with elevated eye pressure without evidence of damage, i.e., normal optic nerve and visual field.  Nine and half percent of those who were watched developed glaucoma after five years, while only 4.4% of those treated with drops developed glaucoma.
If you have above-average eye pressure you don't necessarily need to begin taking eye drops. Not everyone with elevated eye pressure develops glaucoma; in this study, over 90% of those in the untreated group did not show any evidence of damage during the five years of the study. Those of you who are at moderate or high risk of developing glaucoma should be treated.
This study also demonstrated that traditional methods of measuring your eye pressure are more dependent on the thickness of your cornea than previously thought.  Thin corneas measure lower pressures while thicker corneas measure higher pressure. 

Can Vitamins Help?

Ginkgo biloba (GBE) is thought to enhance blood flow and thereby improve visual field damage in some patients with normal tension glaucoma (NTG). A prospective, randomized, placebo-controlled, double-masked crossover trial was performed on patients with visual field loss from NTG. Half of the patients received 40 mg GBE orally three times daily for 4 weeks, then 4 weeks of placebo pills (identical capsules filled with sugar). The other half underwent the same regimen, but took the placebo first and the GBE last. Researchers evaluated visual field tests, performed at baseline and at the end of each phase of the study.

Results showed a significant improvement in visual fields after GBE treatment. No significant changes were found in intraocular pressure, blood pressure or heart rate after treatment. No ocular and systemic side effects were recorded for the duration of the trial.

 

What is the treatment for primary open angle glaucoma?

The aim of treatment is to lower the eye pressure. If the eye pressure is lowered, further damage to the optic nerve is likely to be prevented or delayed. The eye pressure to 'aim for' varies from case to case. It partly depends on how high the original pressure is. Your eye specialist will advise. Eye pressure can be lowered in various ways.

Eye drops

A variety of eye drops can lower eye pressure. They work either to:
reduce the amount of aqueous humour that you make, OR increase the drainage of aqueous humour. Your eye specialist will advise. Some drops work better in some people than in others. Some drops are not suitable if you have asthma. Also, the possible side-effects vary between the different types of drops. So, if the first does not work so well, or does not suit, another may work fine. In some cases, two different types of drops are needed to keep the
eye pressure low.
It is vital to use your drops exactly as instructed. If you are unsure that you are using your drops correctly, ask for advice from your doctor or practice nurse. An eye specialist will keep a regular check on your eye pressures, optic nerves, and field of vision.

Tablets

Tablets work by reducing the amount of aqueous humour that you make. However, side-effects can be troublesome and so tablets are not commonly used these days.

Surgery

An operation called trabeculectomy is an option. This involves creating a channel from just inside front of the eye to just under the conjunctiva. So, the aqueous humour can bypass the blocked trabecular meshwork. In effect, it is like forming a small 'safety-valve' for the aqueous humour. Surgery may be advised if a trial of eye drops has failed to achieve target eye pressures, especially in younger people, or if you have very high eye pressures. Like with all operations, there is a small risk of complications. Also, the operation may have to be repeated in some cases. This is usually because some scar tissue forms at the site of the channel and prevents it working to drain the aqueous humour.

Laser
A laser can 'burn' the trabecular meshwork which improves the drainage of the aqueous humour. Another technique is to destroy parts of the ciliary body which reduces the amount of aqueous humour that is made. However, the reduction in eye pressure after laser treatments often only lasts a short time. So, laser treatments are not commonly done.

Driving and glaucoma

If you are a driver and have glaucoma in both eyes, the law says that you must inform the Driver and Vehicle Licensing Authority (DVLA). You will need to have a special eye test to check on how severely your vision is affected. However, in most cases, vision is not affected too severely and after assessment most people will still be allowed to drive.