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Macular degeneration - causes, symptoms, treatment

 
Macular degeneration is a chronic disease that results in vision loss in the centre of a person’s field of vision. Early symptom detection and diagnosis is important. Treatment may involve special eye medications and medical procedures as well as lifestyle remedies.
 
Macular degeneration is the leading cause of vision loss in people aged over 50 years. It is estimated more than 14% of New Zealanders over the age of 50 years are affected by macular degeneration.  Due to New Zealand’s ageing population, the prevalence of macular degeneration is projected to increase substantially over the next decade.

General information

The macula is the central region of the retina, which is the light-sensitive inner layer of tissue at the back of the eye. The retina processes visual images, with the macula being responsible for central (i.e. straight-ahead) vision.  As the eye ages the macula deteriorates and the central sharp vision that is used for seeing detail is gradually lost. This means tasks such as reading, driving and recognising faces become more difficult. Although it can lead to legal blindness, macular degeneration does not result in total blindness.
 
Macular degeneration differs from glaucoma, which is characterised by gradual loss of peripheral (side-ways vision), and cataracts, in which the normally clear lens of the eye becomes cloudy. Macular degeneration is also known as age-related macular degeneration (or AMD) because it is associated with getting older and mainly affects people later in life. Inherited forms of the disease can, however, affect young people.

Causes

The exact cause of macular degeneration is not known. What is known, however, is that as the eye ages certain structural and functional changes occur in the retina that are important to the development of macular degeneration. Genetic and environmental factors may be involved.  There are two types of macular degeneration: dry and wet.

Dry macular degeneration is the more common and less severe of the two types. It may progress to the wet form over time. Dry macular degeneration has three stages, which may occur in one or both eyes: 

  • Early stage – small yellow deposits called drusen accumulate beneath the retina and may be detected during an eye examination. Vision is not usually affected and there are no symptoms. 
  • Intermediate stage – one or more large drusen are present. There may be a blurred spot in the centre of the visual field. More light may be required to read or do detailed work. 
  • Advanced stage – several large drusen and breakdown of the macula tissue is present. There is blurring of the central vision. Reading is difficult and there is more reliance on peripheral vision.

Wet macular degeneration is characterised by sudden onset and more severe loss of vision. Wet macular degeneration occurs when abnormal blood vessels grow under the retina and leak fluid or blood into the macula region.

Risk factors

Factors that increase the likelihood of macular degeneration occurring include: 

  • age over 50 years 
  • family history of macular degeneration 
  • ethnicity – macular degeneration is more common in Caucasians than in other ethnic groups 
  • smoking 
  • obesity – increases the chance of progressing to more severe macular degeneration 
  • poor diet 
  • cardiovascular disease 
  • high blood cholesterol 
  • high blood pressure.

Signs and symptoms

Macular degeneration is a painless condition. Symptoms usually develop slowly and typically include:

  • difficulty reading or performing activities that require fine vision 
  • need for brighter lighting when reading or doing close-up work 
  • difficulty adapting to low levels of light 
  • reduced intensity or brightness of colours 
  • gradual increase in the cloudiness of central vision 
  • distortion, i.e. straight lines appear wavy or crooked 
  • distinguishing faces becomes difficult 
  • dark patches or empty spaces appear in the centre of your field of vision.

If you experience any of these symptoms you should contact your optometrist or ophthalmologist promptly. Early diagnosis and treatment may reduce vision loss and, in some people, may improve vision.  

Diagnosis

In addition to reviewing your medical and family history, and performing a comprehensive eye examination, an optometrist or ophthalmologist may use the following tests to diagnose macular degeneration:

  • Amsler grid – a tool used to detect distortion in a person’s vision whereby straight lines on a grid appear wavy or crooked, faded or broken 
  • optical coherence tomography (OTC) – a non-invasive imaging test that uses light to produce high-quality images of the different layers of the retina 
  • fluorescein angiogram – an imaging technique involving the use of a coloured dye, which after being injected into the arm travels to the eye where it highlights blood vessels in the retina (only an ophthalmologist will perform this for you).

Treatment

Currently, there are no medical treatments available for dry macular degeneration. However, because it usually progresses slowly, many people with the dry form can live relatively normal and productive lives, especially if only one eye is affected.
 
Several medical treatments are available for wet macular degeneration, although none can cure the condition. The aim of these treatments is to stabilise and maintain existing vision for as long as possible. In some cases, vision can improve. Treatments for wet macular degeneration include:

Medications
Drugs called anti-vascular endothelial growth factor (anti-VEGF) agents can help stop the growth and leaking of new blood vessels in the retina. These drugs are injected directly into the eye. Anti-VEGF drugs available in New Zealand include bevacizumab (Avastin), ranibizumab (Lucentis), and aflibercept (Eylea).
 
Photodynamic therapy
This procedure involves using light to activate a medication that is injected into the arm and travels to blood vessels in the eye. Once activated the medication causes abnormal blood vessels in the eye to close and stop leaking.
 
Photocoagulation
In certain situations, a high-energy laser beam can be used to destroy and seal leaking blood vessels under the macula.
 
Lifestyle changes
The following lifestyle measures may reduce the risk of developing macular degeneration or help to prevent vision loss if macular degeneration has already been diagnosed: 

  • regular eye checks
  • stop smoking
  • exercise regularly and keep your weight down
  • manage other diseases, such as cardiovascular disease, high blood pressure, and high blood cholesterol
  • eat a variety of fruits, vegetables, and leafy greens – these foods contain antioxidant vitamins that may reduce the risk of developing macular degeneration
  • use healthy unsaturated fats, such as olive oil, in cooking and salads
  • include fish and nuts in your diet – these foods contain omega-3 fatty acids, which may reduce the risk of developing macular degeneration
  • in consultation with your doctor, consider taking zinc and antioxidant vitamin (A, C, and E) supplements
  • protect your eyes from sunlight, especially when young
  • consider a suitable supplement ask you optometrist or ophthalmologist for their recommendation.

Further information and support

Macular Degeneration New Zealand Free phone: 0800 MACULA (0800 622-852) Email: info@mdnz.org.nz Website: www.mdnz.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.
Worsley D., Worsley A. Prevalence predictions for age-related macular degeneration in New Zealand have implications for provision of healthcare services. NZMJ 2015;128(1409):44-55.
Mayo Clinic Staff (2012). Diseases and Conditions: Dry macular degeneration (Web Page). Mayo Foundation for Medical Education and Research.
Mayo Clinic Staff (2012). Diseases and Conditions: Wet macular degeneration (Web Page). Mayo Foundation for Medical Education and Research.

Created: April 2015


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