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Understanding Glaucoma, Its Symptoms, Treatment and Prevention
Glaucoma is an eye disorder that, if left untreated, can lead eventually to blindness. It is caused by an increase in intraocular pressure (eye pressure), known as 'IOP' for short,which can damage the optic nerve thereby restricting transmission of visual information to the brain. In the common form of glaucoma, that is 'open angle glaucoma', this can happen slowly and there is usually plenty of time to receive treatment to save your vision.
According to the World Health Organisation, next to cataracts, glaucoma is the second major cause of blindness. It may present with loss of peripheral vision and if this is left untreated, eventually central blindness occurs.
What are its symptoms?
Most types of glaucoma are called 'open angle glaucoma' and are symptomless often going undetected until an evident vision loss occurs which means that there is permanent damage to the optic nerve. You might suspect you have glaucoma if there is a family history of this condition.
Your vision with glaucoma, it's the second leading cause of blindness in IrelandGlaucoma is often discovered when a person attends an optician to get reading glasses and the optician discovers that the eye pressure (IOP) is elevated. Sometimes your own G.P. might notice you have glaucoma when your optic nerve is being examined for other reasons. It is wise to attend an eye doctor if glaucoma is suspected.
If you attend Medical Optics as a glaucoma suspect you will have a full eye examination by a specialist eye doctor and certain tests will also be carried out. These tests include assessment of the optic disc (i.e.optic nerve head) which will be photographed and imaged.A visual field test will also be carried out. If you are diagnosed with glaucoma treatment will be instituted. This usually means you will be taking eye drops.
How is glaucoma detected?
IOP can be measured by an instrument called a tonometer. The eyes are made numb with eye drops so that the instrument can take the measurement.
The applied force in an area of the front of the eye is given in millimetres of mercury (mm Hg). The eye's normal IOP (pressure reading) should be below 21 mm Hg. A high IOP reading indicates that the eyes are producing too much aqueous fluid or not draining properly.
Glaucoma treatment includes eye drops that control IOP. A reading that is over 30 mm Hg means a 40 times higher danger of losing vision from glaucoma compared with a 15 mm Hg or lower IOP reading.
Glaucoma is also monitored by the following methods: determination of the eye's baseline image, examination of the optic nerve and other internal structures. Follow up examinations are important to determine if there is any further progression or damage.
There are currently 3 tests that can discover glaucoma at a very early stage before permanent damage has occured and all good glaucoma treatment centres will have access to at least one of these test machines:
1. Scanning Laser Polarimetry (SLP or GDx) - polarised light is used to measure retinal nerve fiber layer thickness to see if early stage glaucoma is occuring.
2. Optical Coherence Tomography (OCT) typically, a near-infrared light is used to penetrate and capture 3D images to measure the optic nerve and its related structures.
3. Confocal Scanning Laser Ophthalmology laser diagnostic imaging of the optic nerve head.
Visual Field Testing tells you if glaucoma has already damaged your optic nerve and by how much. It is done regularly to determine if there is progressive loss of vision from glaucoma by finding extension of subtle blind spots due to optic nerve damage.You are asked to stare straight ahead and click a button every time a tiny light flashes in the field of vision.
CCT or 'central corneal thickness' is measured by an instrument to determine one of the risk factors for glaucoma.
Gonioscopy this is conducted by an eye doctor to determine the eyes capacity to freely drain aqueous humour (eye fluid) through the drainage angle, a structure inside the eyes.
What are the types of glaucoma?
Primary Open-angle Glaucoma (POAG) and Angle-closure Glaucoma (ACG)
These are 2 major types of glaucoma that pertain to the eye's drainage angle. POAG is the one most people are referring to when they use the term 'glaucoma'. Angle closure glaucoma is much less common in Ireland and typically affects older people with cataracts and sometimes younger long sighted individuals.
The American Academy of Ophthalmology said about 2.2 million of United States population are affected by POAG and this may reach 3.3 million by 2020. It is 3 times more common in African-Americans than non-Hispanic whites. It induces glaucoma-caused blindness to the former 6 times more than the latter. Tunnel vision (only straight-ahead-objects are seen) can result in POAG sufferers whose IOP remains high.
Low-tension Glaucoma (also known as Normal-pressure or Low-pressure Glaucoma)
This is an open-angle type of glaucoma where the cause may be due to narrowing of blood vessels due to spasticity and can sometimes be associated with migraine or Raynaud's disease. Narrowing from arteriosclerosis in older people can also cause this condition. The IOP is normal but visual field loss is suffered because of damage to the optic nerve due to inadequate blood supply. The absence of pain may lead to permanent damage as the disease progress goes undetected until symptoms like tunnel vision appear.
Experts believe that poor blood flow to the optic nerve may be the cause of this condition which is more prevalent among the Japanese, females and those with cardio vascular diseases.
Pigmentary Glaucoma
This is a rare condition where the iris loses pigment that blocks the drainage angle affecting the outflow of aqueous and results in damage from inflammation of the drainage system. Often symptomless, save for slight pain and blurred vision after rigorous activity, this type of glaucoma often affects white males in their mid 30s or 40s.
Secondary Glaucoma
This can be a chronic glaucoma condition that usually develops after suffering from an eye injury or infection, inflammation or tumor. It may also follow lens enlargement from a cataract.
- Acute Angle Closure Glaucoma (or Narrow-Angle Glaucoma)
Those suffering from ACG (or 'acute glaucoma') also called narrow-angle glaucoma, may experience repetitive sudden pain in the eyes and head, dilated pupils, loss of vision, red eyes, halos around lights, and nausea and vomiting. Vision loss progresses with each attack. The eye pressure suddenly become very high due to narrowness or closure of the drainage angle. This condition usually requires immediate treatment often by drops and tablets, and sometimes intravenous injections in hospital, prior to emergency surgery to open the drainage angle of the eye.
Congenital Glaucoma
This inborn eye condition is more common in boys than girls and often diagnosed in the first year of the child's life. The eye's drainage system has narrow angles or other imperfections but this may be hard to notice and children are too young to alert that anything unusual going on.
An eye doctor needs to be consulted should cloudy, white or hazy, enlarged or protruding eyes are observed in a child.
How is glaucoma treated?
Depending on how severe the condition is, glaucoma may be treated by:
1. Eye drops (rarely in combination with oral medication)
2. Laser
3. Surgery
Most cases of glaucoma are controlled very adequately with eye drops alone. Eye drops are very occasionally combined with medication to control glaucoma for a limited period. Laser is used when eye drops on their own do not control glaucoma fully. Surgery is the last option and reserved for a small percentage of glaucoma sufferers who are refractory to eye drop medication.If an eye drop causes discomfort or other problems make sure you talk to your eye doctor rather than stopping the treatment. Often nanother eye drop that suits you better will be prescribed.
How can it be prevented?
Research was conducted in the UK to substantiate the benefits of exercise in reducing the chances of glaucoma. The study established that engaging in physical exercise reduces glaucoma risk factor called low OPP (ocular perfusion pressure- the value of one's IOP or blood pressure) by 25%.
According to its author, University College of London Institute of Ophthalmology's Paul J. Foster, MD, PhD, OPP may largely be influenced by cardiovascular fitness as there could be a link between sedentary lifestyle and increased factors leading to glaucoma. An active lifestyle, he added, may effectively reduce glaucoma and other health problems risks.
The best prevention of glaucoma is to have it diagnosed and treated early in the condition. This means you should be routinely checked on a two yearly basis if you are over 50 years of age. Even if you are in your 20s, 30s or 40s you should have the occasional eye pressure check.