Glaucoma is the name for a group of eye conditions in which the optic nerve becomes damaged by elevated pressure within the eye. This produces a characteristic pattern of visual field loss (loss of side vision). Let us see what causes the intra ocular pressure to rise.

The eye constantly produces aqueous humour, the clear fluid that fills the anterior chamber (the space between the cornea and iris). This 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 filters out of the anterior chamber through a complex drainage system and drains via the venous system. The delicate balance between the production and drainage of aqueous determines the eye's intra-ocular pressure (IOP). Normal eye pressure is maintained when the amount of aqueous produced balances the amount draining away. If it cannot escape, or if too much is produced eye pressure rises and eventually this may damage the optic nerve. This can result in defects in the field of vision, which are not often perceived until they become severe and begin to affect central vision. The normal range of IOP is between12 and 21mm Hg. However, some eyes can tolerate higher pressures than others. That is why sometimes a person with a higher than normal pressure may suffer no damage while another person with an IOP within the normal range may suffer damage to the optic nerve. Glaucoma is such a complex disease and definitely has to do with more than just elevated pressure in the eyes.

Common Types of Glaucoma

Open Angle - also called chronic open angle, wide angle or primary open angle - is the most common type of glaucoma. With this type, even though the anterior structures of the eye appear normal, aqueous fluid builds up within the anterior chamber, causing the IOP to become elevated. Left untreated, this may result in permanent damage of the optic nerve and retina. Eye drops are generally prescribed to lower the eye pressure. In some cases, surgery is performed if the IOP cannot be adequately controlled with medical therapy. It is the most dangerous type for two reasons. Firstly because it is the most common type and secondly because it does not give any symptoms at all. It is only when the visual field is severely affected in the late stages of the disease that the person tends to notice that something is wrong. It is then too late as any field loss is permanent. This type of glaucoma has a prevalence of 2% in the above forty population, meaning two persons in every hundred aged more than forty will suffer from the disease.

Acute Angle Closure - Only about 10% of the population with glaucoma has this type. Acute angle closure occurs because of an abnormality of the structures in the front of the eye. In most of these cases, the space between the iris and cornea is narrower than normal, leaving a smaller channel for the aqueous to pass through. If the flow of aqueous becomes completely blocked, the IOP rises sharply, causing a sudden angle closure attack. While patients with open angle glaucoma do not typically have symptoms, those with angle closure glaucoma may experience severe eye pain accompanied by nausea, blurred vision, coloured haloes or rainbows around lights, and a red eye. This problem is an emergency and should be treated by an ophthalmologist immediately. If left untreated, severe and permanent loss of vision will occur in a matter of days. An angle closure attack will most commonly happen after some time in the dark such as when the person has been watching a movie at the cinema.

Secondary Glaucoma - This type occurs as a result of another disease or problem within the eye such as an inflammation, trauma, previous surgery, diabetes, tumour or certain medications. For this type, both the glaucoma and the underlying problem must be treated.

Congenital - This is a rare type of glaucoma that is generally seen in infants. In most cases, surgery is required.

Signs and Symptoms

Glaucoma is an insidious disease because it rarely causes symptoms. Most glaucoma is painless. A feeling of "pressure" around the eyes is usually due to sinusitis or stress, not raised intra ocular pressure. Moreover, people are unable to self-test the amount of their side-vision.

Glaucoma is often first diagnosed by a simple test of eye pressure during a routine eye examination. When the pressure is higher than the normal range other tests must be done to confirm the presence of glaucoma.  In the uncommon “narrow angle” or “closed angle” glaucoma, there are no symptoms except for blurring after being in the dark for an extended period of time (at the movies, for example); if the angle closes, there will be acute pain and redness. In advanced open angle glaucoma, marked loss of side vision may cause a person to bump into objects outside the field of vision (doorways or walls). That is when the person usually notices there is something wrong and it is already in the late stages of the disease. Therefore, detection and prevention are only possible with routine eye examinations. However, angle closure and congenital glaucoma can cause following symptoms.

Angle Closure (emergency)
• Sudden decrease of vision, misty vision
• Haloes or coloured rainbows around lights
• Extreme eye pain
• Headache
• Nausea and vomiting
• Glare and light sensitivity

Congenital
• Tearing
• Light sensitivity
• Enlargement of the cornea or the eyeball

High risk groups

There is a definite hereditary predisposition for glaucoma and all blood-relatives of a glaucoma patient should be evaluated periodically. Other risk factors include diabetes, high myopia, eye injury, and inflammation. Susceptible patients may develop glaucoma from the overuse of eye drops containing cortisone-related ingredients, the so-called cortisone-induced glaucoma.

Detection and Diagnosis

Because glaucoma does not give symptoms in most cases, those who are 40 or older should have an annual examination including measurement of the intra-ocular pressure. Those who are glaucoma suspects may need more frequent monitoring or additional tests.

Glaucoma evaluation has several components. In addition to measuring the intra-ocular pressure, the eye practitioner will also evaluate the health of the optic nerve, test the peripheral vision and examine the structures in the front of the eye with a special lens before making a diagnosis.

The eye practitioner evaluates the optic nerve and grades its health by noting the cup to disc ratio. This is simply a comparison of the cup (the depressed area in the centre of the nerve) to the entire diameter of the optic nerve. As glaucoma progresses, the area of cupping, or depression, increases. Therefore, a patient with a higher ratio has more damage.

The progression of glaucoma is monitored with a visual field test. This test maps the peripheral vision, allowing the eye practitioner to determine the extent of vision loss from glaucoma and a measure of the effectiveness of the treatment. The visual field test is periodically repeated to verify that the intra-ocular pressure is being adequately controlled.

The structures in the front of the eye are normally difficult to see without the help of a special lens. This special mirrored contact lens allows the eye practitioner to examine the anterior chamber and the eye's drainage system.

Treatment

Glaucoma may be controlled, especially if detected early, by pressure-lowering drops, pills, laser surgery, or surgery to open a new pathway through which eye fluid can drain. The loss of side vision is not reversible i.e any field loss is permanent; so the aim of treatment is to prevent loss in the early stages and to preserve one's remaining vision in the later stages. It must be pointed out that as treatment merely lowers and controls the intra-ocular pressure, it is for life. The patient must never stop the medication without being advised to by the prescribing eye doctor.

The primary choice is using eye drops to lower pressure either by decreasing production of pressure-producing fluid inside the eyeball or by enhancing re-absorption of that fluid.

Optimal medical treatment involves a convenient schedule (instillation once or twice daily), effective pressure lowering, and minimal side effects. A trial period is often necessary until regulation is achieved. Periodic follow-up examinations are required to monitor pressure and visual fields to detect worsening of the disease. Additional treatment may be needed to control the effects of glaucoma.

The prosta glandins (Xalatan, Travatan and Lumigan) are a relatively new type of drops used once daily, at night and which have become very popular in the treatment of glaucoma. They may however cause darkening of the iris colour from hazel to brown. Eyelashes will lengthen and skin will turn darker around the eyes, giving the appearance of a black eye. There is also a persistent redness frequently. However, these side effects are transient in most cases and generally outweigh the disadvantages of other drops as they are very effective in lowering IOPand only need to be instilled once daily.

Beta-blocker eye drops (such as timolol) are given once or twice daily. They may slow the heart rate and worsen underlying asthma or emphysema.

Epinephrine eye drops (such as Propine) may cause rapid heartbeat or red eye.

Dorzolamide (Trusopt) drops should not be given to patients with sulfa allergies.

Pilocarpine, the oldest treatment for glaucoma, is seldom used today unless the person is allergic or non-responsive to the newer drugs.  Side effects were difficult to tolerate, particularly if the drops had to be given four times daily.  The drops constrict the pupil, allowing less light to enter the eye, producing a transient "dimming" of vision or brow ache and difficulty at night and in dim light.

All drops administered over a long period of time may cause a harmless, but annoying eye irritation (redness and dryness) due to sensitivity to the preservatives in the medication.

Your eye doctor, sometimes in consultation with your family doctor, will decide which drop/s are best for you. Every patient and every eye is different regarding its response to medication.

The recent increase in the various kinds of drops available has made the use or oral medications less common. Carbonic anhydrase inhibitors such as Diamox or Neptazane may still have clinical uses as diuretics to suppress the outflow of eye fluid, which lowers eye pressure. Side effects range from mild tingling or intestinal upsets to kidney stones and aplastic anemia (uncommon). They should not be given to people with a sulfa allergy.

Laser surgery is recommended to control pressure for a limited time period. This is a painless procedure usually taking under 15 minutes. It may have to be repeated to produce the desired effect. In situations requiring surgery to control pressure, the procedure (called filtering) must be performed in the hospital.  This surgery establishes new channels for outflow of fluid from the eye.

Having elevated pressure does not necessarily mean you have glaucoma. Some eyes can tolerate increased pressures and have normal optic nerves and visual fields. (The higher the pressure, however, the higher the risk). Regular examinations are necessary to detect changes in the eye that would warrant starting therapy.

If the disease is detected early in its course, and if the patient is cooperative, blindness is unusual. A commitment to a routine of daily drops is necessary however. (Some patients fool themselves by instilling drops only on the days they visit the doctor.)

Having elevated pressure does not necessarily mean you have glaucoma. Some eyes can tolerate increased pressures and have normal optic nerves and visual fields. (The higher the pressure, however, the higher the risk). Regular examinations are necessary to detect changes in the eye that would warrant starting therapy.

Low vision aids, such as hand-held magnifiers, and good illumination will help with reading and other near tasks. Patients should avoid becoming anaemic, as blood supply to the optic nerve may suffer. Smoking should be avoided.

Vision rehabilitation services help people make the most of remaining vision - ask for our advice as to whether you will benefit from rehabilitation if you suffer from glaucoma. 

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Whilst we have taken great care to gather correct information and to keep it current, we cannot guarantee its accuracy and completeness.

The information provided should never be considered a substitute for professional health care by a qualified doctor or other health care professional, which will be tailored to the patient's individual circumstances. We cannot take responsibility if you rely on this information alone.