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Glaucoma - causes, symptoms, treatment

 
Glaucoma is an eye disease in which gradual damage to the optic nerve leads to vision loss. Early diagnosis and treatment is critical to minimise or prevent loss of vision. Although anyone can develop glaucoma, the risk increases with age. Glaucoma is the leading cause of blindness in New Zealand; approximately 2% of New Zealanders over the age of 40 years are affected by glaucoma while more than 10% aged 80 or more have the condition.

General information

Glaucoma is a group of related eye conditions that cause damage to the optic nerve.  Located at the back of the eye, the delicate optic nerve transmits visual impulses from the eye to the brain. Injury or damage to the optic nerve can lead to loss of vision or even complete blindness. The loss of vision is usually gradual and may not be noticed immediately because it first affects peripheral or side vision.

Because vision loss from glaucoma is permanent, the need for it to be detected and treated as early as possible is critical. If not treated, glaucoma will cause progressive vision loss, normally in these stages:  

  • blind spots in your peripheral vision 
  • loss of peripheral vision (tunnel vision)
  • complete blindness.

Glaucoma differs from macular degeneration , which is characterised by progressive loss of central (straight ahead) vision, and cataracts, in which vision loss results from the lens of the eye becoming cloudy.

Risk factors

Because some forms of glaucoma can destroy vision without any obvious signs or symptoms it is important to be aware of the factors that increase the risk of developing glaucoma:  

  • higher than normal pressure inside the eye (which can only be detected with examination by an ophthalmologist (eye doctor) or optometrist
  • age – especially people aged over 60 years
  • ethnic background – people of African & Asian descent are particularly susceptible to some types of glaucoma
  • family history of glaucoma
  • medical conditions – diabetes, heart disease, high blood pressure, or hypothyroidism
  • other conditions – near-sightedness (myopia), far-sightedness (hyperopia), eye injuries, migraines
  • long-term use of corticosteroids – especially eye drops.

Causes

Abnormally high pressure within the eye (intraocular pressure) is usually, but not always, associated with optic nerve damage. The pressure inside the eye increases when the eye’s fluid drainage system fails to function properly.  Glaucoma can develop slowly (chronic glaucoma) or abruptly (acute glaucoma):  

  • chronic glaucoma – blockage of the eye’s drainage channels occurs gradually. It is the most common form and is painless
  • acute glaucoma – blockage in the drainage channels of the eye occurs suddenly. It is painful and can result in permanent vision loss if not treated immediately.

There are different types of glaucoma, with a range of characteristics and causes. Some of these include:  

  • primary open-angle glaucoma – a partial blockage in the eye’s drainage system causes fluid to drain out of the eye too slowly, resulting in a gradual increase in pressure within the eye
  • angle-closure glaucoma – occurs when the iris bulges and blocks the drainage system, causing inadequate fluid drainage and an increase in intraocular pressure 
  • normal-tension glaucoma – the optic nerve becomes damaged even though the pressure within the eye remains normal 
  • developmental glaucoma – occurs in infants and children and usually without symptoms 
  • pigmentary glaucoma – pigment granules in the eye build up and block drainage channels.

Glaucoma may have a genetic link meaning that certain individuals are more susceptible to the disease. A form of juvenile open-angle glaucoma has a clear link with genetic abnormalities.

Signs and symptoms

The two most common types of glaucoma have different symptoms.

Primary open-angle glaucoma: 

  • peripheral vision, usually in both eyes, is lost gradually 
  • advanced stages are characterised by tunnel vision.

Acute angle-closure glaucoma:  

  • eye pain, which may be accompanied by nausea and vomiting 
  • sudden development of visual disturbance 
  • blurred vision 
  • halos (i.e. crowns or auras) are seen around lights 
  • reddening of the eye.

Primary open-angle glaucoma gives few warning signs until permanent damage has already occurred. Regular eye checks are important to detect glaucoma early enough to successfully treat it and prevent further progression.

Diagnosis

In addition to reviewing your medical history, your ophthalmologist or optometrist will perform the following tests to diagnose glaucoma:  

  • measuring intraocular pressure – tonometry is a simple and painless procedure that measures internal eye pressure 
  • optic nerve damage test – instruments that look into the back of the eye are used to check for damage to the optic nerve 
  • visual field test – to check whether a person’s field of vision (specifically peripheral vision) has been affected by glaucoma 
  • measuring corneal thickness – this test, known as pachymetry, determines the thickness of the cornea, which can assist in diagnosing glaucoma. 

Treatment

Treatment for glaucoma will not restore lost vision; it will only prevent further loss of vision. The aim of treatment therefore is to lower intraocular pressure either by increasing the drainage of fluid from the eye or lowering the amount of fluid produced in the eye.  In the case of acute angle-closure glaucoma, urgent treatment (usually both medication and surgery) is required.

Medications
Treatment usually starts with medicated eye drops. Commonly prescribed eye drops include prostaglandins, beta-blockers, alpha agonists, and cholinergic (miotic) agents. 
Medicated eye drops must be used exactly as prescribed otherwise their use could worsen optic nerve damage. If eye drops by themselves do not lower intraocular pressure to the desired level you may be prescribed an oral medication, usually a carbonic anhydrase inhibitor, to reduce your eye pressure.
 
Surgery
Treatment of glaucoma may require surgery if medications do not work or are not well tolerated.  Surgeries to treat glaucoma include:  

  • laser surgery – a procedure called laser trabeculoplasty is used to clear blockages in the eye’s drainage channels 
  • filtering surgery – a procedure called a trabeculectomy is used to create an opening in the drainage system that bypasses blocked drainage channels 
  • drainage implants – in this procedure a small tube is inserted into the eye to increase fluid drainage.

Lifestyle remedies
The following lifestyle changes may help if you have elevated intraocular pressure or glaucoma:  

  • eat a healthy diet – certain vitamins and nutrients may help eye health 
  • exercise safely – regular exercise may reduce intraocular eye pressure 
  • limit caffeine intake – high levels of caffeine may increase intraocular pressure 
  • sip fluids frequently – drinking large amounts of water quickly can cause a temporary increase in eye pressure 
  • relaxation – stress may trigger angle-closure glaucoma so find healthy ways to relax. 

Prevention

The loss of vision with glaucoma can be so gradual that it is not noticed until much of the peripheral vision is lost. For this reason, regular eye checks are recommended for people aged over 40 years.  

Further information and support

Glaucoma NZ
Phone: 0800 GLAUCOMA (0800 452 826)
Email: admin@glaucoma.org.nz
Website: www.glaucoma.org.nz
 
Sight Loss Services
Phone: 0800 555-546
Email: info@sightloss-services.com
Website: www.sightloss-services.com

References

Akpek, E.K., Smith, R.A. Overview of age-related ocular conditions. American Journal of Managed Care 2013;19:S67-S75.
Akpek, E.K., Smith, R.A. Current treatment strategies for age-related ocular conditions. American Journal of Managed Care 2012;19:S76-S84.
Mayo Clinic Staff (2012). Diseases and Conditions: Glaucoma (Web Page). Mayo Foundation for Medical Education and Research.
Ministry of Health (2012). Conditions and Treatments: Glaucoma (Web Page). Wellington: Ministry of Health.
O’Toole, M.T. (Ed.) (2013). Glaucoma. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis: Elsevier Mosby.

Created: April 2015

 

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