About Glaucoma
Glaucoma is the name given to a group of eye diseases where vision is lost due to damage to the optic nerve. Major eye health body Glaucoma Australia says that generally, there are no symptoms or warning signs in the early stages of this eye condition. The loss of sight is usually gradual and a considerable amount of peripheral (side) vision may be lost before there is an awareness of any problem.
The primary problem in glaucoma is damage to the optic nerve whose cells carry messages from your eye to your brain and once damaged, vision is lost permanently. For instance, just as a football needs air pressure to maintain its shape, the eyeball needs internal, or intraocular, fluid pressure to retain its shape and ability to see. The cause of glaucoma is generally the failure of the eye to maintain an appropriate balance between the amount of internal fluid produced and the amount that drains away. When this is out of balance, eye pressure can rise to dangerously high levels – causing glaucoma. However, glaucoma is a problem not only when the pressure is high; in some people it can cause damage when the pressure is normal or low.
Glaucoma cannot be self-detected. In most cases there are no symptoms or early warning signs to let you know there is something wrong with your eyes. The only way to check if you have glaucoma is to have an eye exam including an optic nerve check which is simple and completely pain-free.
A person with glaucoma's peripheral (side) vision gradually becomes impaired and it can lead to blindness Photo Credit: www.envisioneye.com.au
Who Gets Glaucoma?
There are different types of glaucoma. Primary open angle glaucoma is the most common form of the disease and mainly affects people over 40 years of age.
People who have diabetes, suffer from migraines, have had an eye injury or been on a prolonged course of cortisone (steroid) medication or have a history of high or low blood pressure, are more at risk of developing the disease. A family history of glaucoma increases the risk. People of African descent are more likely to get glaucoma than Caucasians and Asians have higher risk of a type of glaucoma called ‘angle closure’. Infantile glaucoma can occur from birth or can develop in a child’s early years.
Glaucoma Australia has a risk calculator on its website to help people assess their risk level of the disease.
Types of Glaucoma
The following information has been re-published courtesy of Glaucoma Australia.
Primary Glaucomas
Primary Open-Angle Glaucoma
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
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 (PAC) and Primary Angle-Closure Glaucoma (PACG)
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.
Normal tension (or Low tension) Glaucoma
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
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
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
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.
Pigment-Dispersion Syndrome (PDS)
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.
Pseudo-Exfoliation Syndrome and Glaucoma
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.
Neovascular (Rubeotic) Glaucoma
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
Mixed Mechanism Glaucomas
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
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.
Iridocorneal Endothelial Syndrome
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.
Steroid-Induced Glaucoma
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.
Published date: 01 September 2016 Reviewed date: 17 April 2020
Author: Sophie Koh, National Professional Services Adviser at Optometry Australia
Bio: Sophie Koh is an experienced optometrist who started her career in the Northern Territory. She has broad experience working in public health and corporate settings across metropolitan, rural and outback Australia. She has extensive experience working in ophthalmology teams and training nurses in East Timor, Papua New Guinea and Solomon Islands. Sophie studied her undergraduate degree at the University of Melbourne and was amongst the first cohort of graduates to achieve the ACO Certificate in Ocular Therapeutics. She is currently the National Professional Services Adviser at Optometry Australia. She is passionate about public health and Indigenous eye health. She is devoted to empowering students and colleagues to improve their knowledge and skills so they can play a wider role in improving the health and wellbeing of our underprivileged communities locally and overseas.
Disclaimer: No information provided on the Good vision for life website is intended to constitute or substitute advice from visiting an optometrist. Many factors unknown to us may affect the applicability of any information on this website. You should seek appropriate personalised advice from a qualified optometrist about any eye health and vision conditions.
