Glaucoma and monitoring tests

Patient Information Leaflet

Introduction

This leaflet explains more about glaucoma and the tests used to diagnose and monitor it.

What is glaucoma?

Glaucoma is a condition which can affect sight, usually due to a build-up of pressure within the eye.

It often affects both eyes, usually to varying degrees. One eye may develop glaucoma quicker than the other.

In some people, the pressure may be normal, but damage still occurs because of weaknesses of the optic nerve.

What causes pressure within the eye?
A fluid (called aqueous humour) is produced inside the eye by a layer of cells on the muscle that moves the lens in the eye. The fluid is needed to:

• Provide nutrients to the front of the eye, especially the cornea and lens that have no blood vessels.
• Remove waste products from the eye.

The fluid drains mainly through a structure called the trabecular meshwork. This meshwork lies in the angle where the cornea meets the iris.

The normal pressure in the eye is between 10 and 24 millimetres of mercury (mmHg). If for any reason the fluid is blocked and cannot get out, the pressure can rise and glaucoma may occur. A diagnosis of glaucoma is given if you have damage to your optic nerve.

Ocular Hypertension- Normal eye pressure range is between 10 and 24. If you have received a diagnosis of Ocular Hypertension then at some point your pressure has been measured above the 24 level. At this stage your optic nerve is still healthy, and your visual field test is deemed normal.

Approximately 10 percent of untreated ocular hypertension will convert to glaucoma within five years.

You may be started on eye drops to bring the pressures down, and to prevent any damage occurring in future. It is vital that if you have been started on eye drops that you use them as prescribed to keep the pressure down so that your optic nerve stays healthy and your visual field test remains normal.

What types of glaucoma are there?
There are two main types of glaucoma:

• Open-angle
• Narrow-angle

Both types may happen by themselves, which is known as primary glaucoma, or as a result of another eye condition, known as secondary glaucoma.

Open-angle glaucoma
Open-angle glaucoma is more common and affects two per cent of adults over 40. It is more likely to happen

• With increasing age – it affects 10 per cent of those over 75.
• In African races.
• In those who are very short-sighted.
• In those with diabetes.
• In those with family history of it.
• In those who have used steroids for a long time.

This type of glaucoma is when the drainage channel is open. Its exact cause is unknown. Although the drainage angle is open and appears normal when examined, research has found that there is resistance to fluid draining out at the trabecular meshwork.

This resistance to drainage causes the pressure to rise, which causes damage to the optic nerve. This damage is possibly caused by the force of the pressure or reduced blood supply to the nerve.

Open-angle glaucoma often develops gradually over time and affects both eyes. People frequently do not realise their sight is being damaged because the first part of the eye to be affected is the outer field of vision (peripheral vision).

The danger of this condition is that the eye seems perfectly normal and the loss of vision is so gradual and painless that people are often unaware of it until the damage is considerable and permanent.

At first, the damage to vision tends to be in the shape of an arc, either a little above or below the centre of the field of vision.

If untreated, this progresses until most of the outer field of vision is lost and there is only a small central tunnel of vision left. Eventually, this too can be lost, causing complete blindness.

As most patients have few or no symptoms, it is important to have your eye pressure checked regularly, especially if there is a family history of glaucoma.

Narrow-angle glaucoma

This is where the drainage angle between the cornea and iris becomes closed. With this type of glaucoma, there will be symptoms such as colour haloes, a headache or brow ache. There may possibly be more severe symptoms of an acute attack, including pain, nausea (feeling sick) and reduced vision. This is an eye emergency and needs to be checked urgently at either an eye emergency clinic or an emergency department, preferably at an eye hospital.

What tests are used to diagnose glaucoma?

There are several glaucoma tests, and they are often carried out during the same appointment to ensure results are as accurate as possible. They are painless and quite quick.

Optic nerve assessment

The optic nerve is usually examined using a slit lamp, which is a microscope with a very bright light. You will need to put your head in a    headrest. The ophthalmologist will look at your eyes using the light and a lens held near to your eye.

We may have to use eye drops to widen the pupils of your eyes so that we can get a clear view. The eye drops can make your sight blurry for a while, so we advise you not to drive to this appointment. People who have glaucoma often have an optic nerve which looks abnormal where it has been damaged.

Eye pressure test

Measurement of the pressure within the eye is called tonometry. It uses an instrument called a tonometer to measure the pressure inside your eye.

The ophthalmologist will put some drops of anaesthetic (a painkilling medication) into your eye. Then, yellow / orange dye is used to temporarily stain the tears. You will need to put your head in a headrest, and then the ophthalmologist will shine a blue light on your eye.

We use a small, round, flat instrument to painlessly flatten the cornea of your eye. We can measure the pressure of your eye by how much the cornea flattens.

Central corneal thickness measurements

This is performed by anaesthetising the eye with drops and placing a small ultrasonic probe on the centre of your cornea for a few seconds. The measurements from this can help the ophthalmologist check how accurate the pressure values are from the eye pressure test. This is a measurement of the thickness of your cornea (which is located at the front of the eye). It is very important we have an estimation of how thick your cornea is, as it can impact greatly on what is “safe” for you in terms of pressure levels within your eye.

Examination of the drainage angle
To do this examination, we put anaesthetic drops into your eye, and then put a contact lens on your eye. This allows your ophthalmologist to see in the angle between the cornea and iris, to see if it is open or closed. They will also examine the trabecular meshwork where the fluid drains out of your eye.

Other tests

Other tests that are sometimes used to diagnose or monitor people with glaucoma are as follows:

All day measurements of eye pressure (phasing)

Eye pressure can vary a great deal throughout the day and is often higher in the early morning. Therefore, we may need to assess the pressure every two hours over an eight to 24 hour period. This is called phasing. It is useful if your eye pressure is borderline or if glaucoma is progressing even though you have normal eye pressure measurements.

Visual field test
A visual field test is sometimes called perimetry. It checks for missing areas in the field of vision and can be used to monitor progression of glaucoma.

For the test, you will need to put your head in a headrest. You will be shown a series of lights on a screen, and you will need to press a buzzer when you see one. Some dots will appear in your peripheral vision (around the sides of your eyeball), which is where glaucoma begins. One eye is tested at a time.

If you cannot see the spots in your peripheral vision, it may mean that glaucoma has damaged your vision.

Three-dimensional (3D) scanning of the optic nerve

A quick and painless scan can be performed of the optic nerve using various specialised scanning systems, including Heidelberg Retinal Tomography and Optical Coherence Tomography. This can produce an accurate 3D image of the optic nerve and retinal nerve fibres. It can be useful in monitoring glaucoma in some patients.

Virtual and face to face reviews

Your consultant and the glaucoma team regularly undertake a detailed review of your medical records and make a clinical decision on what are the most important diagnostic tests for you to have at the time of your review. You may be allocated to a clinic based on the tests you require, and these clinics are as follows:

Face to face

This may include a variety of glaucoma tests and examination by the glaucoma team. Please allow at least 2 hours for this type of review. Please try to not drive to this type of appointment as drops may be required to dilate your pupils to give a wider view of the eye on the slit lamp. Your vision will return to normal within about 4 hours after the dilatating eye drops have been used.

Technician and Nurse-Led Clinics

Our team of Ophthalmic Technicians and Nursing staff run a number of virtual clinics. The majority of these are at Corbett Outpatient Centre in our Diagnostic Hub, but there are also some that run at Russells Hall Hospital. Within these clinics you will have a selection of tests carried out that have been requested by your Consultant or our Advanced Glaucoma Practitioner.

The virtual clinics we run are as follows:

VGC1 – this involves a visual acuity check followed by a measurement of the pressure in your eyes. This will most likely be done with a “puff of air”, but other methods of pressure measurement are available should this be required.

VGC2 – this involves a visual acuity check, scans and photos of the back of the eye, and a measurement of the pressure in your eyes.

VGC3 – this involves a visual acuity check, a visual field test and a measurement of the pressure in your eyes.

Glaucoma assessment – this involves all tests in VGC1 to VGC3.

This means your visit may last anywhere between 10 minutes to an hour, depending on the clinic you have been booked into.

All results obtained in the Technician/ Nurse Led Clinics will be reviewed by an Ophthalmologist or an Advanced Glaucoma Practitioner who will then be in touch with you via a letter or telephone call to inform you of the outcome and the future management of your case. Technicians are unable to give you any results on the day.

Interpreting your Results Letter

Below are some terms you may see mentioned in your results letter, along with a definition of what they mean.

• Visual Field test (VF test) – this is the test of your peripheral vision- This may be classified as “within normal limits,” “outside normal limits” or “borderline.” Your responses on the visual test are compared to a database or “normal” and healthy individuals who are within your age range. If you are classified as “within normal limits” this means that you are performing at a level expected for your age range. “Outside normal limits” means the opposite- you are below what we expect for your age range. A “borderline” classification means that it is highly likely your visual field test result is normal with some abnormal features.

The reliability of your test may also be referred to in your letter. Poor or low reliability may mean you are either “trigger happy” during the test, you are not keeping your eye on the fixation point and/ or responses are inconsistent due to reduced concentration during the test

It is also important to note that there can be a “learning effect” with performing visual field tests. If you are fairly new to visual field testing, and you do receive an “outside normal limits” result, this does not necessarily mean that you have glaucoma. It could be that you have not quite grasped how to carry out the test reliably, and with time you may well improve.

• Optical Coherence Tomography (OCT) scan- At the Corbett Diagnostic Hub, we carry out scans of various parts of your eye. These scans show up any areas of loss or thinning of layers at the back of the eye, and any signs of damage to the optic nerve. Classifications of “within normal limits” “outside normal limits” and borderline, may be used in your results letter. Like with the visual field test, your results are compared to a database of healthy age- matched patients – “within normal limits,” indicates that you fall within the range of healthy, age-matched individuals. If the results are worse than those seen in the healthy age matched normal population then you be classified as “outside normal limits.” A “Borderline” classification, indicates that the results are likely to be within the normal range with some abnormal features.
• Intraocular pressures (IOP) – This is a measurement of the pressure level within your eyes. Normal pressure tends to range between the levels of 10 and 24mmHg and fluctuates depending on time of day. It is also important to note that even if your pressure falls within the normal range, you can still go on to develop glaucoma.
• Narrow angles- Scans of the drainage angles may be showing that there is very little space or room, for the fluid in the eye to pass through and exit the eye. This may mean that further, and more in-depth scans, may be required at The Birmingham and Midland Eye Centre, or you may need to be seen face to face at Russells Hall Hospital for a more in-depth examination of your drainage angles.
• Open angles- scans of the drainage angles show the path for fluid to drain out of your eye are open, and unless there is any congestion within the angle itself, the fluid should be able to drain freely out of your eye at a steady rate.
• Glaucoma Suspect- This means that there are one or more suspicious signs of glaucoma that have been detected in one or both of your eyes. This could be one or more of the following:

1. Your optic nerve, in one or both eyes, may have an appearance that resembles what is frequently seen in glaucoma patients.
2. Your visual field test for one or both eyes may show patterns of loss consistent with those seen in glaucoma patients.
3. The pressure in your eye or both eyes may have been recorded above the 24mmHg level

At this stage a firm diagnosis of glaucoma is not possible. There could be various reasons why the reviewing Consultant, cannot be completely certain at this stage that you have Glaucoma. Further monitoring will be required to be sure. In some cases, particularly when there is a very strong suspicion of glaucoma, treatment is initiated. This usually takes the form of eye drops, which must be used as prescribed. Drops MUST NOT be missed and/ or stopped for any reason without seeking advice from a Medical Professional. Glaucoma treatment is a lifelong treatment, and not a “one-off course.”

• Ocular Hypertension – Normal eye pressure range is between 10 and 24. If you have received a diagnosis of Ocular Hypertension then at some point your pressure has been measured above the 24 level. At this stage your optic nerve is still healthy, and your visual field test is deemed normal. You may be started on eye drops to bring the pressures down, and to prevent any damage occurring in future. It is vital that if you have been started you on eye drops that you use them as prescribed to keep the pressure down so that your optic nerve stays healthy and your visual field remains full or within the normal range.
• Primary Open Angle Glaucoma – If you have received this diagnosis then damage has occurred to the optic nerve and there may be an accompanying visual field loss too. This is the most common form of glaucoma and tends to occur gradually due to eye pressure increasing.
• Normal Tension Glaucoma – If you have this diagnosis then damage has again occurred to the optic nerve and again there may be accompanying visual field loss. With normal tension glaucoma, the pressure within the eye to remain within the normal range of 10 to 24 but may be high for the structure of the eye. Initial treatments offered, usually drops or laser treatment, will still target the pressure and aim to reduce it to the lowest level possible.
• Narrow Angle Glaucoma – Patients who receive this diagnosis have narrow drainage angles, meaning that the fluid within the eye may not be draining away as quickly as it should be. Over time, and with age related changes to the eye, the angles can narrow even further. Damage to the optic nerve and surrounding retinal layers may be apparent, and there may be accompanying visual field loss. Initial treatment for this type of glaucoma may involve laser and/or drops. In some cases, removal of maturing cataracts can help to permanently open drainage angles up.

Frequently Asked Questions

1. I have a diagnosis of glaucoma, am I going to go blind?

Treatment has come a long way over the years, and there are numerous interventions at our disposal which aim to preserve your sight throughout the remainder of your lifetime.

This is a two-way process however, and success of treatment may rely on you. This means you must consistently administer all drop treatments as prescribed, and you must attend all your monitoring appointments at the Hospital, as well continue regular optician visits.

Your Ophthalmologist may also recommend supplements to help to keep cells at the back of the eyes healthy. These can be bought over the counter in most pharmacies, but always speak to your Pharmacist or GP before taking any supplements.

2. Am I required to notify the DVLA if I have a diagnosis of glaucoma?

Car drivers need only notify the DVLA if they have a diagnosis of glaucoma in both eyes with visual field defects in both eyes, if one eye remains healthy then the DVLA do not need to be notified. If glaucoma is diagnosed in one eye only, but the fellow eye is compromised with another ocular disease then, again, the DVLA must be notified.

Notifying the DVLA is your responsibility. You will be sent to have a special form of visual field test with an Optometrist that is affiliated with the DVLA, and determines your legal standing for driving.

3. Can I drive to my Eye Clinic appointments?

For all appointments in the Diagnostic Hub at Corbett Hospital, no drops will be instilled, so you may drive to these appointments.

If you receive an appointment for a Consultant or Practitioner Led Clinic at Russells Hall Hospital, then you should not drive to these appointments as you may well require dilating drops; which can blur vision for up to eight hours after they have been instilled.

4. Do I still need to go to the optician for regular sight tests?

Regular sight tests with the optometrist at the optician are essential for everyone, as not only do they prescribe glasses to correct your vision when necessary, but they also detect conditions such as glaucoma and other eye conditions at the earliest possible opportunity. Glaucoma usually has no symptoms in the early stages, and the earlier that treatment is initiated the more chance we have of preserving good levels of vision.

Patients that are referred to the hospital eye service in the later stages of glaucoma will already have extensive, irreversible damage and in this case, treatment is to preserve the vision that is left.

5. Should I use my eye drops on the day of my appointments?

Yes, you should always continue to use your drops as prescribed. If you do not, it is not known how effective the treatment is in keeping your pressures low. For example, if you attend clinic and your pressures are raised, we cannot be sure if this is due to your treatment not being effective or because you have not used your drops on the day of appointment.

What if I have any problems or questions after reading this leaflet?

If there is anything you do not understand, or you are concerned or worried about any part of the treatment, contact:

The Urgent Referral Clinic team at Russells Hall Hospital Eye Clinic on 01384 456111 ext. 3633.

Eye emergency, out of hours

In case of an eye emergency after the closing hours of the Eye Clinic at Russells Hall Hospital (including weekends and bank holidays), please contact:

Birmingham and Midland Eye Centre on 0121 507 4440

The doctor on call is usually based at the Eye Centre, City Hospital,    Dudley Road, Birmingham. They may need to call you back, and if necessary, they will arrange an appointment for you.

Note: the information in this booklet is provided for information only. The information found is not a substitute for professional medical advice or care by a qualified doctor or other health care professional.

Always check with your doctor if you have any concerns about your condition or treatment. This is only indicative and general information. Individual experiences may vary, and all the points may not apply to all patients at all times. Please discuss your individual circumstances with your eye doctor.

Where can I find out more?

The Royal National Institute of Blind People (RNIB) booklet, ‘Understanding Glaucoma’, contains more information. You can also visit the RNIB website:

http://www.rnib.org.uk/eye-health-eye-conditions-z-eye-conditions/glaucoma

Authors: Julia Phillips (Advanced Glaucoma Practitioner), RGN, Ophthalmic Nurse Training, BSc (Hons), Glaucoma Specialist MSc modules and training. Non-medical prescriber.

Rachael Smith: Glaucoma technician Lead

This leaflet can be downloaded or printed from:

http://dgft.nhs.uk/services-and-wards/ophthalmology/

If you have any questions, or if there is anything you do not understand, please contact the Russells Hall Hospital switchboard number on 01384 456111 and ask for the relevant department who issued this leaflet.

If you have any feedback on this patient information leaflet please email dgft.patient.information@nhs.net

This leaflet can be made available in large print, audio version and in other languages, please call 0800 073 0510.

Glaucoma & Monitoring Tests/JP/RS/ST/01.2025 v5 – review 10/2027 – DGH ref.: DGH/PIL/01156