Age-Related Macular Degeneration

What is Age-Related Macular Degeneration?

Age-Related Macular Degeneration (AMD) is a common, painless eye condition in which the central portion of the retina deteriorates leading to a loss of central, detailed vision.

AMD is the leading cause of legal blindness and severe vision loss in Australia.

Who is at Risk of Age-Related Macular Degeneration?

The strongest risk factor for AMD is increasing age but it is not a normal or inevitable consequence of ageing. Positive family history and smoking are other strong risk factors.

Impact of Age-Related Macular Degeneration

Age-Related Macular Degeneration damages the macula which is responsible for detailed vision such as reading and the ability to recognise faces. The peripheral vision is usually unaffected.

Types of Macular Degeneration

In the early and intermediate stages of AMD, there is a build-up of lipids and proteins called drusen under the retina. While the visual clarity is usually minimally affected during these stages patients often notice that they require brighter light to be able to read. 

The late-stage is divided into two forms: Dry and Wet AMD.

Dry AMD

The dry form of AMD is a gradual process where the retinal cells deteriorates resulting in a slowly progressive loss of central vision. Although there is currently no treatment or prevention, this is an area of active research.

Wet AMD

The wet form of AMD is characterised by a more rapid loss of central vision. This is the result of small blood vessels growing underneath the retina. This process is termed Choroidal Neovascularisation and the abnormal blood vessel may bleed or leak and scar tissue can form.

What are the Symptoms of Macular Degeneration?

In the early stages, there may be no symptoms. One of the earliest manifestations is a need for brighter light when reading. In the late stage, blurred or distorted vision is commonly reported. Near (reading) vision is commonly affected to a greater degree than distance vision. 

Diagnosis and Prevention of Macular Degeneration

The early detection of AMD is important as steps can be undertaken to help slow its progression. In its early stages, macular degeneration may not result in noticeable visual symptoms but it can be detected with a detailed dilated eye examination in conjunction with Optical Coherence Tomography (OCT) scanning of the macula.

In the later stages, patients may be aware of blurred vision or distortion.

A patient suffering blurred vision or difficulty vision focus should never be dismissed as just a part of getting older. 

Macular Degeneration Prevention

The following preventive measures have been suggested for slowing down the progression of macular degeneration: 

Smoking is the most important modifiable risk factor for AMD development and progression. Smokers have an increased risk of developing AMD compared to none smokers.

Dietary measures may also reduce the risks

• Eat a healthy, well-balanced diet
• Eat dark green leafy vegetables and fresh fruit daily
• Eat foods that are high in  Omega-3 fatty acids such as fish and nuts
• Choose low glycemic index (low GI) carbohydrates instead of high GI

 
Vitamin Supplements & the Age-Related Eye Disease Study (AREDS)

Supplements may be of value in patients with Intermediate AMD where there is a substantial collection of drusen at the macula or in patients who already have late AMD in one eye. In patients with early AMD, the risk of progression to late AMD is lower and the role of supplementation is less clear.

The Age-Related Eye Disease (AREDS) study showed that supplementation reduced the risk of progression to wet AMD by 25% in high-risk individuals, but does not prevent the progression of dry AMD.

The original daily AREDS Supplement formula included:

• Vitamin C 500mg
• Vitamin E 400IU
• Zinc (as zinc oxide) 80mg
• Copper (as cupric oxide) 2mg,
• Beta-carotene 15mg (excluded from commercial formulations as this may increase the risk of lung cancer in smokers)

There are a number of commercially available AREDS supplements on the market in Australia.

Wet Macular Degeneration Treatment

First-line therapy since 2007 has been with intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) drugs. These drugs do not cure the disease but aim to suppress the growth and leakage of the abnormally leaking and bleeding blood vessels. They stabilise vision in most cases, and up to a third of patients experience a significant improvement in vision. Treatment should be started with as little delay as possible as these agents cannot reverse scarring or retinal thinning which occurs in many untreated cases.

The two most commonly used agents are Lucentis (ranibizumab) and Eylea (aflibercept). In some cases, off-label Avastin (bevacizumab) is used. Numerous new drugs are in development.

What if Macular Degeneration is Untreated?

If Wet Age-Related Macular Degeneration goes untreated, central vision loss can develop rapidly. The longer it is left untreated, the greater risk of permanent visual deficit.