Glaucoma comprises a group of eye diseases in which the pressure inside the eye (the intraocular pressure) causes damage to the nerve at the back of the eye (the optic nerve). This can result in a progressive loss of peripheral side vision (the visual field) and ultimately can cause complete blindness. In the majority of cases the intraocular pressure is raised. In some eyes, however, the pressure may be within normal limits, but damage still occurs because of weaknesses of the optic nerve.

What causes pressure within the eye?

Fluid (aqueous humour) is produced inside the eye by a layer of cells on the muscle (the ciliary body) 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), to remove waste products from these structures and to create a pressure within the eye to maintain its shape and allow it to function correctly. The aqueous fluid drains mainly through a structure called the trabecular meshwork that lies in the angle where the cornea meets the iris. The normal pressure in the eye is between 12 and 21 millimeters of mercury (mmHg). If for any reason the outflow of aqueous fluid is obstructed the pressure can rise and glaucoma may occur.

Types of Glaucoma

There are two main types of glaucoma:

• Closed-Angle - where the angle between the peripheral cornea and iris becomes closed
• Open-Angle - where this angle is open

Both types may occur either spontaneously (primary glaucoma) or as a result of another eye condition (secondary glaucoma)

Closed-angle glaucoma

Closed-angle glaucoma is relatively uncommon in the UK and Western countries. It tends to affect those who are very long-sighted. It is more common in the elderly and Asian races. It can run in families.

Typically symptoms are acute and severe, the eye suddenly becoming very red and painful, with accompanying nausea and vomiting. The pressure in the eye is usually very high and the vision extremely blurred. Occasionally it may not present with an acute severe attack, but with a series of mild episodes characterised by eye ache and the appearance of misty rainbow coloured rings around lights. These typically occur in the evening, when the pupil of the eye has become dilated in the dark, precipitating the attack.

Acute closed-angle glaucoma is an ocular emergency, requiring prompt treatment in hospital with eye drops and tablets to reduce the pressure and prevent the eye from going blind. Once the attack has been controlled, laser surgery (called a YAG laser iridotomy) is required to make a hole in the outer border of the iris, to relieve the obstruction and prevent further episodes. This laser treatment is not painful. Usually the other eye is also treated because there is a high risk that it will develop the same problem. With prompt treatment there is usually good recovery of vision. Delay may cause a permanent loss of sight. Occasionally the eye pressure may remain raised, despite treatment and further surgical measures may be necessary.

Open-angle Glaucoma

Open-angle glaucoma is more common and affects 2% of adults over 40. It is more frequent with increasing age (affecting 4% of those over 65), in African races, in those who are very shortsighted and those with diabetes.

Its exact cause is unknown. Although the drainage angle is open and appears normal to examination, an increased resistance to aqueous outflow at the trabecular meshwork has been found. This resistance to drainage causes the pressure to rise, resulting in damage to the optic nerve, possibly by direct mechanical compression or a reduction of its blood supply.

Open-angle glaucoma is typically a chronic, insidious disease, affecting both eyes. Damage to the optic nerve causes a slow loss of peripheral (side) 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 its presence until damage is extensive and permanent. The early loss in the field of vision in glaucoma is typically in the shape of an arc a little above or below the centre. If untreated the field loss progresses until most of the peripheral side vision is lost and only a small central "tunnel" of vision remains. Eventually, with progression, this too can be lost causing complete blindness.

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

The detection of chronic open-angle glaucoma

The detection of glaucoma depends on:

• Measurement of the pressure in the eye
• Examination of the field of vision
• Examination of the optic nerve

Measurement of the pressure within the eye is called tonometry. It can be performed in a number of ways, all of which are painless and do not harm the eye. "Air-Puff" tonometry is a method often employed by opticians. An instrument placed in front of the eye, but not touching it, is used to puff a jet of air into the eye. This air jet flattens the cornea and the degree of flattening relates to the eye pressure.

It is a method that is easy to use but can over-estimate the pressure. The most accurate and widely practiced system and the one preferred by most Ophthalmologists, is "Goldmann applanation" tonometry. In this technique, the eye is anaesthetised with eye-drops and then a yellow dye is used to temporarily stain the tears. With the patient's head placed in a rest, a blue light is shone on the eye. A small, round, cone-shaped prism is then advanced towards the eye and used to painlessly flatten the cornea, the degree of flattening once again relating to the eye pressure.

Examination of the field of vision is called perimetry. It is needed to detect and quantify defects (scotoma) in the field of vision at an early stage and monitor any progression. The normal field of vision of each eye extends for about 120 degrees up and down and for 150 degrees from side to side. Many instruments have been developed for examining visual fields. Patients are usually asked to place their head in a rest and watch a target in the middle of a bowl-shaped screen. While watching the target, a series of lights are presented on the screen and the patient is asked to indicate, by pressing a buzzer, which ones he/she can see. From these responses the field of vision and any defects caused by glaucoma can be mapped out.

The optic nerve can be examined using a special torch-like instrument called an ophthalmoscope. In glaucoma the optic nerve is often abnormal on examination, with a characteristic "cupping" or excavation of its surface where nerve fibres have been damaged and lost.

Additional tests that can be useful in the management of the glaucoma patient are:

Examination of the drainage angle

This is performed by anaesthetising the eye with drops and placing a contact lens on the eye which allows your Ophthalmologist to directly see the angle between the cornea and iris to see if it is open or closed and to examine the trabecular meshwork where the aqueous fluid drains out of the eye.

Central corneal thickness measurements (corneal pachymetry)

This is performed by anaesthetising the eye with drops and placing a small ultrasonic probe on the centre of the cornea for a few seconds. Such measurements can help the Ophthalmologist verify the accuracy of the intraocular pressure values obtained by tonometry. If the cornea is thicker than usual the pressure can be over-estimated i.e measured as falsely high. Similarly if the cornea is thin, the pressure can be underestimated.

All day measurements of intraocular pressure (phasing)

Intraocular pressure can vary by as much as 4mmHg (and more in the glaucoma patient) during the day. Typically (but not always) measurements are higher in the early morning. It may be necessary therefore to assess the pressure every 2 hours over a 12 to 24 hour period. This is called phasing and is useful if pressures are border line or if glaucoma is progressing despite normal pressure measurements in the clinic.

3-dimensional scanning of the optic nerve using
Heidelberg Retinal Tomography and Optical Coherence Tomography

A quick and painless scan can be performed of the optic nerve using various specialised scanning systems including Heidelberg Retinal Tomography (HRT) and Optical Coherence Tomography. This can produce a high accurate 3-D image of the optic nerve and can be a useful monitoring tool.

Treatment of Open-angle Glaucoma

The main treatments are aimed at lowering the pressure within the eye. This can be achieved either by reducing the amount of aqueous fluid produced or opening up the channels by which fluid leaves the eye. Treatments may be:

• Medical (using eye-drops or tablets)
• Laser
• Surgical

In most cases treatment usually starts with eye-drops. If this does not succeed then either laser or surgery is offered.

Medical Treatment

There are a number of medications available to lower the pressure within the eye. Some of these reduce the amount of aqueous fluid, while others open up the drainage channels. They include:

• "Beta blocker" drops

These include Timoptol (Timolol), Betaxolol (Betoptic), Betagan. These reduce aqueous fluid production and are usually very efficacious in reducing the pressure. Occasional side effects may include wheezing, shortness of breath and dizziness due to slowing of the heart rate.

• "Alpha agonist" drops

These include Adrenaline (Eppy), Propine, Aproclonidine (Iodipine), Brimonidine (Alphagan). Some of these reduce aqueous production others have more effect in opening the drainage channels. Older agents such as Eppy and Propine may have little effect in some patients. Newer agents such as Iodipine and Alphagan are more efficacious. All these agents may occasionally cause inflammation and allergic responses of the conjunctiva causing redness, discharge and itching.

• "Miotic" drops

These include pilocarpine drops. They open the drainage channels and improve the outflow of aqueous fluid. They are effective and inexpensive and often used to augment other drops, but in drop form they usually have to be administered up to four times a day. They cause the pupil to become very small and this may interfere with vision and cause headaches.

• "Carbonic Anhydrase" Inhibitors

These include Acetazolamide (Diamox) tablets and Dorzolamide (Truspot) and Brinzolamide (Azopt) eye drops. They reduce the production of aqueous fluid. Diamox tablets are very potent in reducing the eye pressure, but can cause tingling in the hands and feet, generalized tiredness, sickness, vomiting and diarrhoea. Rarely, they cause kidney stones and blood problems. Trusopt and Azopt eye drops are less effective, but do not cause so many side effects.

• "Prostaglandin Analogue" drops

These include Lantanoprost (Xalatan), Bimatoprost (Lumigan), Travoprost (Travatan) and Saflutan (Tafluprost) drops. They increase the outflow channels and are the newest group of drops to be introduced into glaucoma treatment. They need only be given once a day, usually at night. They are very efficacious in most eyes and typically well tolerated by patients with few side effects. They have revolutionised the medical treatment of glaucoma. They can cause redness of the eyes, pigmentation of the iris and darken the colour of the eyes and also cause the eyelashes to become darker and longer.

• Combination Eye Drops

In order to improve compliance and for the convenience of patients there are numerous combination drops which contain two of the above groups of drops. Commonly used preparations include Cospot (Timoptol and Trusopt), Combigan (Timoptol and Alphagan), Xalacom (Latanoprost and Timoptol), DuoTrav (Travoprost and Timoptol) and Ganfort (Bimatoprost and Timoptol).

Laser Treatment

If treatment with drops fails to lower the eye pressure to a satisfactory level then laser treatments can be offered. Lasers are complex constructions of mirrors, gases, crystals and cooling systems that generate extreme energy to produce a uniform beam of light. This light energy can then be used to burn, cut or split tissues, without the need for surgical incisions or cutting open the eye. Laser treatments for glaucoma include:

• Argon Laser Trabeculoplasty (ALT)

An Argon laser is used to burn tiny areas of the trabecular meshwork. This localised burning causes shrinkage, which is thought to open up adjacent areas of the meshwork. It is a quick outpatient procedure. The eye is first anaesthetised with drops and the patient is asked to place their head on a rest. A contact lens is then placed on the eye and the laser treatment is performed. Treatment is painless, but is only successful in about 50 to 70% of cases.

• Selective Laser Trabeculoplasty (SLT)

This is a newer but similar treatment to ALT, which uses a Q-switched 532 nanometer Nd: YAG laser. It appears to have the same efficacy as ALT but causes far less tissue damage. It is designed to selectively target the cells that are responsible for pumping fluid out of the drainage system of the eye (the pigmented trabecular meshwork cells). It is postulated that the laser stimulates the trabecular cells to release chemical mediators that naturally clear the drainage system (trabecular meshwork) without the need to cut or damage the tissues. It has been suggested that long-term pressure control may be better with this laser modality and this is the subject of continuing research. Professor O'Brart was one of the first surgeons in the UK with access to this laser system and has performed a number of important clinical research trials in this area. His studies suggest that SLT is a very useful treatment modality which is very safe and in 65% of patients can reduce the pressure by an average of 30% from baseline. It can be used in conjunction with glaucoma eye drops or as an alternative. It is a simple and typically painless out-patient procedure, requiring the patient to put their chin on a rest while laser pulses are delivered to the drainage system of the eye via a contact lens. The procedure takes 5 to 10 minutes per eye. The eye is anaesthetised with eye drops. Recovery is rapid with only minimal blurring of vision for a few hours and minor inflammation for a few days, treated with eye drops.

• Cyclodiode laser ablation

This is generally reserved for very aggressive and advanced glaucoma cases that have not responded or will not respond to medical or surgical therapy. The procedure can be performed as a day-case treatment, but requires an injection of a local anaesthetic behind the eye. A laser probe is placed onto the surface of the eye and pulses of laser energy passed through the eye wall to reach the surface of the ciliary body, causing small burns. This results in a decrease of aqueous fluid production. Cyclodiode laser ablation has been shown to be more efficacious than previous modalities of ciliary body destruction such as cryotherapy and diathermy, resulting in less cases of hypotony (eye pressure becoming too low). Following cyclodiode laser treatment, the eye can be inflamed for a few weeks. As this treatment is reserved for the most difficult cases, repeat applications of laser may be required.

Glaucoma Surgery

Surgery for open-angle glaucoma is considered in cases uncontrolled by medical treatment. The most widely practiced operation is a "trabeculectomy". The aim of this operation is to create a passage to drain aqueous fluid from the front of the eye, through the eye wall and into the space beneath the conjunctiva. It can be performed both under general or local anaesthetic. The conjunctiva (the skin over the white of the eye) under the upper eyelid is first opened and retracted back. A small trap door is then fashioned in the sclera (the wall of the eye) at the edge of the cornea. A hole is then made under the trap door into the front of the eye and a section of iris under the hole is removed. The trap door is then sewn down, loose enough to allow fluid out of the eye but not too loosely so that the eye might collapse. Finally the conjunctiva is sutured back in place.

Generally it is a successful operation, with good pressure control in up to 90% of cases. Complications such as bleeding and excessive drainage can lead to blurred vision, but in the majority of cases this is transient and vision generally returns to the level it was before surgery.

Excessive scarring under the conjunctiva can lead to drainage failure and following surgery it may be necessary to release some of the stitches holding the scleral trap door and/or to use a fine needle to cut scar tissue to optimise drainage. Drainage failure tends to be more common in people of African origin, young patients, those who have had previous eye surgery and those who have used eye drops for many years. In such cases special chemicals, called "anti-metabolites", can be used at the time of surgery to reduce scarring.

In recent years a number of alternative "non-penetrating" glaucoma drainage operations have been developed such as "Deep Sclerectomy" and "Viscocanalostomy". These techniques have been designed to avoid making a full-thickness drainage hole into the front of the eye in order to avoid some of the early complications such as over-drainage and bleeding that can occasionally occur after trabeculectomy. Professor O'Brart has been directly involved in research within this area and has published a number of scientific papers comparing these techniques with trabeculectomy. His results, published in the British Journal of Ophthalmology, indicate that while non-penetrating techniques reduce early complications, success rates are less than with conventional trabeculectomy. Professor O'Brart has in the past been extensively involved with clinical trials investigating the efficacy of more advanced non-penetrating glaucoma operations compared to trabeculectomy.

Information for Patients Booked for Trabeculectomy

Before Surgery

If patients are scheduled for a general anaesthetic, they must not eat or drink anything for nine hours before the operation.

If patients are to have only a local injection or topical anaesthesia a light meal up to four hours before is acceptable. If admission to hospital has been scheduled for example at 8.00 am, the patient need only avoid eating breakfast, but if admission time is in the afternoon, a light breakfast may be eaten and then nothing else until after the operation.

All valuables should ideally be left at home and eye make-up should not be worn to hospital. As the eyes may be sensitive to sunlight after surgery, it is advisable to bring sunglasses.

Any medications, other than eye medication, should be continued, unless advised to the contrary by the eye surgeon. All current medications should be taken to hospital, as the anaesthetist may wish to see them.

Patients, who are staying overnight in hospital, will need to bring nightclothes and toiletries. Day case patients will not usually be required to change into a hospital gown, so loose fitting, comfortable clothes should be worn to the hospital.

Prior to admission, all patients should arrange to be collected from hospital as they must not drive themselves home following surgery.

Upon arrival at hospital

Patients should report to the hospital reception desk or private patients' office at the time advised. Admission details will be sent by the hospital prior to admission. For private patients, if they have private health insurance, the hospital will require details of the insurance cover, otherwise payment in advance is required. Following registration, patients are taken to either a cubicle in the day ward or to their room where they are prepared for treatment and will meet the anaesthetist (if applicable).

Prior to general anaesthesia, most anaesthetists require all patients over the age of 60 to undergo precautionary health checks, comprising an ECG, chest x-ray and blood tests and, if these had not previously been performed, then they will be done on admission and prior to surgery.

Preparation for treatment

During the hour prior to surgery the eye will be prepared for surgery and eye drops will be administered - these are quite painless. They may include drops to dilate the pupil.

The Anaesthetic

The operation may be carried out under local or general anaesthesia and unless there is any specific medical reason for either one, the decision is usually left up to the patients themselves. Most trabeculectomy and viscocanalostomy/deep sclerectomy operations are now performed under local anaesthesia, thereby allowing patients to return home soon after surgery.

The administration of local anaesthesia causes little or no discomfort. No needles are put into the eye itself and once the anaesthetic has taken effect, no pain will be felt, although there may be a general awareness of movement of the eye.

After Surgery

The operation usually takes between 15-20 minutes, following which a plastic shield is placed over the operated eye before patients are accompanied back to their cubicle/room where family or friends may join them.

Even when the operation is performed under general anaesthetic, most people find that they are ready to leave hospital within a couple of hours of surgery, although it is suggested that they rest quietly for the remainder of the day. Before leaving patients are asked to make an appointment for the first post-operative consultation, typically the following day, and given eye drops containing cortisone and antibiotics to administer for several weeks, whilst the eye is healing.

Unless advised otherwise, patients may begin eating normally at any time after the operation, although it is sensible that the first meal is a light one. All prescribed medications should continue to be used after leaving the hospital.

Post-operative vision varies from one patient to the next. Typically after trabeculectomy some blurring of vision during the first six weeks is not uncommon. The operated eye may appear red for the first 3-4 weeks following surgery, but this is quite normal and once the eye has settled down it will look clear and healthy. There is usually little pain after surgery although for a few weeks a gritty sensation and bruised feeling is common. Stitches are used to close both the scleral "trap-door" and the conjunctiva. The deep stitches closing the "trap-door" do not require removal unless excessive scarring causes the drainage to fail, in which case they can be lasered or removed to improve drainage. The surface sutures closing the conjunctiva are designed to fall out by themselves after 4 to 6 weeks.

Post Operative Care

• Do not rub or press the operated eye and wear the eye shield provided for the first 7 nights to avoid inadvertently rubbing it whilst asleep. Try to sleep on the side not operated upon
• Patients must rest for the first 7 days after surgery, thereafter all normal activities can be resumed, but please take care when around small children and animals
• Patients may shower, bathe and wash their hair whenever they wish, but avoid getting dirty or soapy water in the operated eye for the first two weeks
• If the eye becomes sticky, the eyelids may be gently bathed with cotton wool balls and cooled boiled water
• Keep all follow up appointments and take medication as directed

Post operative Consultations

Patients will be asked to attend their first post-operative visit on the day following surgery. Post-operative check-ups help the doctor to monitor the healing and visual progress, as well as providing the patient with the opportunity to ask any questions they may have.

Most people will then be required to return after 1 week and then patients are routinely seen at the 2 week, 1 month and 3 month stages after surgery. These visits are essential to ensure that the operation is working well and the eye pressure is normal. As scarring after surgery can occur, and seal the drainage, the doctor may need to cut stitches and scar tissue with a fine needle to prevent this happening. All eye drops should be brought to each post-operative visit.

In Case of Emergency

Modern trabeculectomy is an extremely safe operation, affording excellent results. However, no surgical procedure is guaranteed to be without complications and problems may occur, albeit rarely.

In the unlikely event of a post-operative problem, please contact Professor O'Brart's office on 01702 586656.

Do not wait for the next appointment if any of these conditions are experienced:

• Sudden worsening of vision
• Onset of pain in the eye which will not go away
• The development a shadow in the vision
• The eye becomes more red and sticky
• A pus-like discharge from the eye

Eye Drops

It is important that patients use the eye drops provided as prescribed during the post-operative period.

How to use eye drops:

• Wash hands and shake the bottle well
• Tilt head back, open eye and look up
• Gently pull lower eyelid down to form a pocket
• Squeeze one drop into the pocket formed, be careful not to touch the eye
• Gently close the eye holding the lower lid out
• Release the eyelid and blink a couple of times
• Gently wipe away any excess liquid with a clean tissue

If this procedure is difficult, try looking in a mirror or else lie down and tilt the head back with the eyes wide open. Put the drop in the corner of the eye by the nose then, keeping your eyes open, roll the head from side to side.

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