The term Glaucoma refers to a characteristic pattern of damage to the optic nerve which currently cannot be reversed. For all types of glaucoma, early detection and prompt effective treatment is vital to reduce visual damage.
Clinicians will refer to someone as a ‘glaucoma suspect’ if they think the person might be showing early signs of glaucoma but they are not yet sure. Many people suspected of having glaucoma at this stage turn out not to have it at all, but some do develop it in time and it is these people who can benefit the most from timely treatment. If someone has a very high intraocular pressure or very advanced optic nerve damage then the diagnosis of glaucoma is usually straightforward. However sometimes it is not entirely clear whether someone has glaucoma or not. The early signs of glaucoma can be subtle, and many glaucoma patients have a normal pressure.
Primary Open-Angle Glaucoma (POAG) is the most common form of glaucoma in Australia. It is a condition in which the optic nerve is damaged, in most cases by high eye pressure, leading to loss of peripheral vision. The rise in pressure and subsequent optic nerve damage is usually due to impaired drainage of fluid out of the eye. Most patients have no symptoms of the condition as there is no pain and in the early stages, vision seems normal.
Acute angle-closure glaucoma is when the pressure inside the eye rapidly increases due to the iris blocking the drain through which fluid travels out from the eye. An attack of acute angle-closure is often severe. Symptoms are pain, nausea, blurred vision and redness of the eye. Immediate medical help should be sought. If treatment is delayed there can be permanent visual damage in a short time. Usually, laser surgery performed promptly can clear the blockage and protect against visual impairment. The narrow angles that lead to angle-closure can be opened by laser surgery, allowing fluid to leave the eye without obstruction.
Primary Angle-Closure is the result of inherited narrowness of the drainage angle of the eye. As the lens of the eye grows throughout life, the tendency to drain-narrowing becomes more marked with advancing years. It is more common in long-sighted eyes, older people, and women.
Optic nerve damage can occur in people even though they have low or normal eye pressure. Even though eye pressure is in the normal range, there is good evidence to show that lowering the pressure with eye drops and sometimes laser or surgery can help preserve patients’ vision. It is also widely recognised that in about 1/3rd of cases of glaucoma the characteristic optic nerve changes and visual field loss can develop in an eye with normal pressure – this is termed normal tension glaucoma.
Childhood glaucoma is a rare form of glaucoma caused by an abnormal drainage system. It can exist at birth or develop later. Parents may note that the child is sensitive to light, has enlarged and cloudy eyes which water excessively. Surgery is usually needed.
Glaucoma in older children (greater than 2 years old) and adolescents is similar to glaucoma in adults. Glaucoma in children of all ages is rare, unlike adult open angle (chronic) glaucoma, which is relatively common. Glaucoma affects approximately 1 in 2000 children.
Secondary glaucomas can develop as a result of other disorders of the eye such as injuries and previous eye conditions. The prolonged use of cortisone (steroid) medication has a tendency to raise eye pressure and therefore can lead to secondary glaucoma.
Pressure can be elevated if the trabecular drainage tissues become blocked by particles. Pigment dispersion syndrome is one example of an underlying eye condition that can lead to such a block. The focusing lens of the eye is held in position by taut scaffolding called the zonule. If the iris (the coloured part of the eye) bows backwards, it can rub against these zonules. The pigment granules, which give the iris its colour, may be dislodged. They flow with the aqueous fluid until the trabecular mesh traps them as the fluid leaves the eye -much like a strainer traps tea leaves. As more and more pigment granules become caught, the trabecular drain works less and less efficiently. The eye pressure starts to rise.
In some eyes with raised intraocular pressure (IOP) and glaucoma, many tiny white flakes can be seen when viewed through a slit lamp microscope, lying on the edge of the pupil, and on the front surface of the crystalline lens. These white flakes have the appearance of microscopic dandruff and are usually accompanied by a mild dispersion of pigment granules from the back surface of the iris, with an accumulation of this pigment in the tissues of the trabecular meshwork. This is different from a condition called pigment dispersion syndrome. About 50% of the time, only one eye of a patient is affected by the pseudo-exfoliation syndrome.
The normal eye has a very high demand for nutrients such as oxygen to allow it to function normally. Various processes ensure the delivery of oxygen to these tissues via the ocular circulation. However, some diseases may result in the eye being starved of blood and oxygen which may lead to a cascade of processes finally resulting in neovascular glaucoma
Combined mechanism glaucomas refers to an eye with elevated pressure in which both open-angle and angle-closure glaucoma mechanisms are present. Usually, the structure of the eye is similar to that found in eyes with angle-closure glaucoma – that is; the globe is somewhat smaller than idea
Traumatic glaucoma refers to cases in which a direct injury to the eye has led to the development of glaucoma. Glaucoma is the name given to a group of eye diseases in which the optic nerve at the back of the eye is slowly destroyed.
The cornea is the clear window in front of the coloured part of the eye (the iris). It has five layers to it and the inner layer is called the endothelium. The endothelium is a single layer of cells that do not regenerate. Its purpose is to pump fluid out of the cornea, effectively preventing it from becoming waterlogged.
Treatment with steroids can elevate the pressure in the eye. This is termed Steroid- Induced Ocular Hypertension. If there is persistent eye pressure elevation then damage to the optic nerve of the eye can occur with corresponding damage to the peripheral vision, this is termed Steroid Induced Glaucoma.
Sturge-Weber Syndrome is a congenital condition which can have ocular, neurological and skin manifestations. It is present at birth, but it is not a hereditary or genetic condition. It often involves the skin of the scalp and face, around the eye, on one side. There are masses of abnormal dilated veins which on the skin are called a naevus flammeus or port-wine stain. Glaucoma in Sturge-Weber Syndrome occurs because of the abnormal blood vessels in and around the eye.
Developmental glaucoma is an umbrella term for a glaucoma due to a relatively rare group of eye disorders characterised by abnormal development of the front part of the eye known as the anterior chamber. People with this underlying anterior segment dysgenesis (ASD) have a significantly increased risk of glaucoma developing. Developmental glaucoma includes the following conditions:
Charles Bonnet Syndrome – It is thought that nearly one third of people with low vision (of any cause) will develop Charles Bonnet Syndrome. In studies of glaucoma, it was found that nearly 1 in 4 (23%) glaucoma patients experienced this phenomenon, which involves visual hallucinations.