When light hits the back of the eye, tiny cells convert the light into nervous impulses. These travel across the retina, through the optic disc, to the brain. Glaucoma is a group of diseases which cause these nerves to become damaged. When this happens the nerves become unable to send the impulses, which leads to blind spots, initially out of the corner of the eye. If the condition is not treated, the blind spots get larger and can lead to blindness. It is known that pressure in the eye is an important factor in this condition. The production and drainage of “water” in the front of the eye affects the pressure. If this gets out of balance the pressure in the eye can increase. Glaucoma can be controlled by using eye drops to reduce the pressure in the eye.
There are several types of glaucoma:
- Chronic open angle glaucoma also known as chronic or primary open angle glaucoma is the most common type. This develops slowly so any damage to the optic nerve and loss of sight is gradual. The term open angle refers to the angle between the iris and sclera which is normal.
- Acute angle-closure glaucoma is an uncommon type where the angle is narrowed and is a contrast to acute angle glaucoma. In this condition there is a sudden increase in the pressure within one eye. The eye quickly becomes painful and red.
- Secondary glaucoma can have various causes which can cause a rise in eye pressure. For example, it may develop as a complication to some eye injuries.
- Congenital glaucoma is where glaucoma is present from birth.
Chronic Open Angle Glaucoma
In chronic open angle glaucoma there is a partial blockage within the trabecular meshwork, a sponge-like tissue located near the cornea that drains aqueous humour (clear, plasma like fluid) from the eye into the blood stream. The reason why the trabecular meshwork becomes blocked and drains poorly is not fully understood. If the drainage is faulty, the aqueous humour builds up, increasing the pressure within the eye.
The increased pressure in the eye can damage the optic nerve and the nerve fibres running towards it from the retina. The retina contains the seeing cells at the back of the eye. Damage to parts of the nerve and retina can lead to permanent patches of vision loss and in some cases it can eventually lead to total blindness.
Chronic open angle glaucoma can affect both of eyes. However, it can often progress quicker in one eye compared to the other.
Difference Between Increased Eye Pressure And Chronic Open Angle Glaucoma
Glaucoma means that part of the optic nerve is damaged, usually caused by increased pressure in the eye (intraocular pressure.) However, about 1 in 5 people with glaucoma have eye pressure in the normal range. This is called normal pressure glaucoma. In this condition, factors such as poor blood supply mean that the optic nerve is prone to damage from even the most modest pressure.
In contrast, some people have an increased eye pressure with no ill effect to the optic nerve or visual loss. Raised eye pressure without glaucoma is known as ocular hypertension. However, statistically, if your eye pressure is high, you will have ocular hypertension and you have a much higher risk of developing glaucoma and visual loss.
If an examination reveals that you have high intraocular pressure, your doctor should talk to you about your individual risk of developing glaucoma. In a recent study it showed that if you do have ocular hypertension, you have a higher individual risk of developing glaucoma and it is likely you may benefit from having treatment to lower your eye pressure.
Glaucoma is a common condition in the UK. About 1 in 50 people over the age of 40 has glaucoma. This increases to about 1 in 10 people over the age of 75. Glaucoma can affect anyone, but it is more common if you:
- Have a family history of glaucoma.
- Have diabetes.
- Are very short sighted.
- Are from African or Afro-Caribbean origin.
Most people with glaucoma are unaware of any problems until quite a bit of visual loss has occurred. There are usually no symptoms at first, no pain or redness in the eye. This is because the peripheral vision (outer field) is the first to go. Central vision, what you use to focus on, e.g. when reading or looking at a specific object, is unaffected until relatively late in the disease. As glaucoma usually affects both eyes, it can be quite deceiving as it may not affect them equally. The better eye may compensate for the weaker one for a while if it starts to lose patches of visual field.
Untreated glaucoma is one of the world’s leading causes of blindness. Some elderly people with glaucoma may put their failing vision down to age. They might not have gone many years with out getting their eyes checked and may be needlessly lose their sight. If glaucoma is diagnosed and treated early enough, blindness can be prevented.
Everyone over the age of 35 should have their eyes checked by an optometrist at least every five years. If you are over 50 it is recommended you have a check every 2 to 3 years. Eye checks will detect early signs of glaucoma before you may notice any symptoms. This is particularly important if you are in any of the at-risk groups listed above.
Certain people are entitled to free eye tests from the NHS. They include:
- People over the age of 60.
- People over 40 with a first-degree relative (mother, father, sibling) with glaucoma.
- If you receive income support or pension credit (other benefits may also qualify).
- If your Ophthalmologist (eye doctor) believes you may have glaucoma.
If you have been diagnosed with glaucoma you should tell your close family members so that they can be tested.
The eye test usually involves examining your eyes with a special light and magnifier called a slit lamp. The back of your eye where the optic nerve leaves your eye (the optic disc) will be examined. There are recognisable changes that can be seen in this area in someone with glaucoma. The optic disc takes on a typical appearance and is said to be cupped. A special photograph may be taken of your optic disc to use as a reference for any future eye checks.
The pressure in your eyes (intraocular pressure) will also be measured. The thickness of your cornea may be measured as well, as the thickness of your cornea can affect your intraocular pressure reading. A special lens may be used to examine the drainage area (trabecular meshwork) of your eye. This examination is called gonioscopy. They may test your field of vision also to check how much you can see whilst you are looking forward. Remember, it is usually your peripheral vision that is affected first.
The treatment will aim to lower your eye pressure, by doing this further damage to the optic nerve is likely to be prevented or delayed. Unfortunately, treatment cannot restore any sight that has already been lost. Optimal eye pressure varies from case to case and partly depends on how high your original pressure was. Your eye specialist will advise. There are various ways that eye pressure can be lowered.
A variety of eye drops can lower eye pressure. They work either to:
- Reduce the amount of aqueous humour that you make (betablockers are commonly used).
- Or to increase the drainage of aqueous humour (eg, prostaglandin analogue drops).
Some drops work better in some people than in others and some drops are not suitable for everyone and the possible side-effects vary between the different types of drops. For example, betablocker drops may not be suitable if you have asthma or heart disease. If the first drops don’t work so well, or don’t suit, another may work fine. In some cases, two different types of drops may be needed to keep the eye pressure low.
Your eye specialist will keep a regular check on your eye pressures, optic nerves, and field of vision. How often you need to attend check ups will depend on your particular situation, but it is important to attend follow-up appointments.
Tablets work to reduce the amount of aqueous humour that you make. Side-effects can be troublesome and so tablets are not commonly used these days.
If eye drops are not helping to lower your eye pressure enough, laser treatment may be suggested. A laser can burn the trabecular meshwork to improve the drainage of the aqueous humour. The treatment only takes a few minutes. A special contact lens is placed on your eye to help focus the laser beam. Patients report feeling a small pricking sensation and notice some flashing lights but the procedure is usually easily tolerated.
Another treatment is to use a laser to destroy parts of the ciliary body. This reduces the amount of aqueous humour that is made. Despite this, sometimes eye drops are still needed after laser surgery.
If other treatments are not effective, an operation called trabeculectomy is an option. By creating a channel from just inside the front of the eye to just under the conjunctiva, the aqueous humour can bypass the blocked trabecular meshwork. This forms a kind of small safety-valve for the aqueous humour. Surgery may be advised if a course of eye drops has failed to achieve the desired eye pressures, especially in younger people, or in people with 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.
It is important to mention that most people treated for glaucoma will not go blind. However, in order to have the best chance at preserving your sight, it is very important that you follow the treatment plan outlined by your doctor.
Driving and Glaucoma
Many people will be allowed to drive after being diagnosed with glaucoma. Even if vision is reduced in one eye, you may still be allowed to drive if your vision is good enough in the other eye. However, you will need to seek advice from your eye specialist. If you have glaucoma causing loss of vision in both eyes, the law states that you must inform the Driver and Vehicle Licensing Agency (DVLA). The DVLA will usually contact your eye specialist and ask them for a report about your condition. The DVLA may also arrange an eye examination of their own for you with an optometrist.
Acute Angle-Closure Glaucoma
Acute angle-closure glaucoma (AACG) occurs when the pressure inside your eye gets too high too quickly. It is an extremely important that it is treated quickly as it can lead to permanent loss of vision. AACG is sometimes referred to as acute closed angle glaucoma or acute glaucoma.
In AACG, there is a sudden blockage around the trabecular meshwork and the aqueous humour fluid unable to drain out of the eye. More fluid is still being made, causing the pressure inside the eye to start rising quickly. As the pressure rises, the optic nerve at the back of your eye can become damaged and your vision can be affected.
Some people are more prone to develop AACG because of the anatomy of their eye. For example, if the area near the base of the iris is quite narrow, the trabecular meshwork can get blocked more easily. Or, if the lens is thicker and sits further forward than normal, it can have the same effect. Some people have a narrow drainage angle or a shallow anterior chamber. This can make you more at risk of developing acute glaucoma. Some people may have a thinner than normal iris, which is more floppy and more likely to cause blockage of the trabecular meshwork.
The iris muscles are responsible for controlling the size of your pupil. Commonly, in someone who is prone to AACG, it occurs when their pupil dilates (gets bigger). The lens will stick to the back of their iris meaning that the aqueous humour is not able to flow from the posterior chamber of their eye through the pupil to the anterior chamber. This blockage of fluid causes the pressure in the posterior chamber to rise. The aqueous fluid collects behind the iris and causes the iris to bulge forwards, blocking the trabecular meshwork and preventing drainage of the aqueous fluid from the eye. This in turn causes the pressure inside the eye to rise rapidly. This is more likely to happen if you have a thin, floppy iris or a shallow anterior chamber.
If you are prone to AACG there are some situations that may trigger it. An attack of AACG is more likely to come on when your pupils is likely to be more dilated. For example, whilst watching television in dim light or during a moment of stress or excitement.
Some medicines can also trigger AACG in people who are prone to it. However, for the general population, the chance of getting acute glaucoma with these medicines is very small so they are commonly prescribed without great concern. If you have been warned that you may be prone to AACG, inform your doctor before starting new medication or eye drops, especially if it is one on the list below.
Commonly used medicines which may trigger AACG are:
- Eye drops used to dilate (enlarge) the pupil – these may be used for eye checkups.
- Antidepressants of the tricyclic or SSRI types.
- Some of the medicines used to treat nausea, vomiting or schizophrenia (a type called phenothiazines).
- Ipratropium (used for asthma).Topiramate.
- Some medicines used to treat allergies or stomach ulcers, such as chlorphenamine, cimetidine and ranitidine.
- Medication used during a general anaesthetic.
About 1 in 1,000 people get AACG. It is more likely in people over the age of 40, and most often happens at around 60 to 70 years of age. It is more common in people who are long-sighted and in women. It is also more common in Southeast Asian and people indigenous to far northern America and Greenland (Inuit).
If one of your close relatives (mother, father, siblings) has had AACG, you have an increased risk of developing it as eye shape is often inherited. If this is the case, you should go for a checkup with an optometrist.
The symptoms usually start suddenly. They include:
- Sudden, severe pain within your eye and an ache around your eye.
- Redness of your eye.
- The pain may spread around your head and feel like a severe headache.
- Blurred or reduced vision, often with circles seen around lights.
- Some people develop nausea, vomiting, or abdominal pain.
- Your eye might feel hard and tender.
As explained above, symptoms may begin in a situation of dim lighting, sudden excitement, after taking certain medicines, or after a general anaesthetic.
In some cases, an attack of AACG can last up to a few hours and then symptoms can improve again. However, attacks will usually return. Each time that you have an attack, your vision may be damaged further. If you experience these symptoms you should see a doctor urgently, in case you need treatment to prevent a more severe attack.
A diagnosis is made from the symptoms and the appearance of the eye. A provisional diagnosis may be made by any doctor. The diagnosis can be confirmed by an examination by an eye specialist. This usually involves examining the eye using a special light and magnifier called a slit lamp which measures the pressure in the eye. A special lens can also be used to examine the outflow channels around the trabecular meshwork area of your eye. This is called gonioscopy.
Quick treatment is needed for AACG. You should be seen by an ophthalmologist (eye specialist) as soon as possible. If it will take time getting an appointment with the ophthalmologist, some treatment can be started. Do not try to cover the affected eye with a patch or a blindfold, this will only make your pupil dilate further and this can worsen the situation.
The first treatment is medication to lower the pressure within the eye. There are different types of medicine and eye drops that may be used in various combinations. Treatments may include:
- Eye drops containing betablocker medication aim to reduce fluid in your eye. Steroids may be used to reduce inflammation.
- An injection of a medicine called acetazolamide.
- Pilocarpine eye drops which can cause your pupil to constrict, helping move the iris away from the trabecular meshwork. This helps to open the obstruction and allow the flow of aqueous humour fluid.
You may also be given painkillers and ant sickness medication if needed.
Once the pressure in your eye has gone down, further treatment is needed to prevent AACG from coming back. This involves using laser treatment or surgery to make a small hole in your iris. The hole allows fluid to flow freely around your iris and can stop the iris bulging forwards and blocking the trabecular meshwork.
- Laser treatment is called peripheral iridotomy. This is the usual treatment. Two small holes are made in the iris using a laser. The holes are almost unnoticeable to the naked eye.
- Surgical treatment called surgical iridectomy is another option. A tiny, triangular hole is made in the iris. The hole is visible afterwards as a very small, black triangular mark at the edge of your iris.
Usually, laser or surgical treatment will be advised for the other eye as well, often at the same time. This is to prevent AACG occurring in the other eye. Sometimes eye drops are needed as long-term treatment to help regulate the pressure in the eye.
If the treatment is started quickly, the outlook is good. Your eye can recover and laser treatment or surgery can prevent the problem coming back. If the attack is severe, or if treatment is delayed, the high pressure within the eye can damage the optic nerve and blood vessels. If this is the case, there is a risk that your vision will be permanently damaged in the affected eye.
Driving And Glaucoma
Many people will be allowed to drive after recovering from AACG. Even if vision is reduced in one eye, you may still be allowed to drive if your vision is good enough in the other eye. However, you will need to seek advice from your eye specialist. If you have glaucoma causing loss of vision in both eyes, the law states that you must inform the Driver and Vehicle Licensing Agency (DVLA). The DVLA will usually contact your eye specialist and ask them for a report about your condition. The DVLA may also arrange an eye examination of their own for you with an optometrist.
As explained earlier, some people have an increased risk of getting AACG because they have a shallow anterior chamber or narrow drainage angle. Sometimes, this can be detected in a routine eye examination. You may be told about this and advised to be careful with certain medicines and eye drops. If you are at very high risk of AACG, you may be advised to have treatment prevent it.
Be aware of the symptoms of AACG. If you develop a red eye with pain or vomiting, or a red eye with reduced vision, seek medical advice immediately. If you take a new medication or have eye drops to dilate your pupil, and have symptoms of AACG, seek medical advice immediately. Tell your doctor about the medication and symptoms. This will make it easier for the problem to be diagnosed early.
Our Appointments Team have a dedicated and caring approach to finding you the earliest appointment possible with the best specialist.
If you do not have a GP, then we have an in-house private GP practice that you can use. Alternatively we can suggest the most appropriate course of action for you to take, given your location and individual circumstance.
If you have medical insurance (e.g. Bupa, Axa PPP, Norwich Union), you will need to contact your insurer to get authorisation for any treatment and, in most cases, you will require a referral letter from your GP.