Age-related macular degeneration (AMD)

As the macula ages, many people develop a form of AMD called ‘early’ AMD. This generally doesn’t cause any symptoms and does not always lead to advanced AMD (Wet AMD or Geographic Atrophy).

If it does progress to advanced AMD, you may notice symptoms such as:

• problems or changes in your central vision, with your peripheral vision remaining normal
• losing the ability to see fine details, both close-up and at a distance (for example, you may see the outline of a clock but not be able to tell what time it is)
• blurred or distorted vision
• a blind spot in your central visual field
• not being able to see as well in low light
• straight lines appearing wavy or crooked

If these symptoms are not investigated, formally diagnosed or left untreated, the central vision could get worse. This can have a significant effect on your daily life and may prevent you from working and driving, or to recognise faces.

AMD is caused by the gradual deterioration of the macula, primarily due to ageing and genetic factors, with a past history of smoking and nutrition throughout life being other important contributory factors.

No single exact cause of AMD exists, and its development and progression aren’t fully understood, but multiple processes are thought to contribute to its development, including oxidative stress and chronic inflammation.

In some people, the macula will show mild signs of ageing as early as 55 years old. This is known as early AMD, which slowly progresses to more advanced forms of AMD. Dry AMD is diagnosed when multiple spots of waste material, called drusen, are detected at the macula.

Wet AMD occurs usually as a late consequence of dry AMD, when abnormal blood vessels grow, these leak fluid and blood (hence the word ‘wet’). If this condition is left untreated, it can progress quickly and cause severe damage to the macula, potentially leading to a permanent loss of central vision. However, the risk of losing all vision with AMD is usually low, as the peripheral vision remains intact.

A late and advanced form of dry AMD also exists, called geographic atrophy, where the macula tissue wastes away; the consequences on vision can be severe, but the condition generally progresses slowly.

An eye doctor will check for AMD using a comprehensive eye exam which includes:

• visual acuity tests – an eye specialist measures vision ability at various distances
• pupil dilation – eye drops are used to widen the pupil and allow a close-up microscopic examination of the retina
• OCT scanning (optical coherence tomography) – a quick but very detailed scan of the retinal structure, this is the main test for diagnosing this condition
• autofluorescence Imaging – another imaging test, involving a bright flash of light giving information about the health of the pigment layer beneath the retina
• ocular angiography – a special dye is injected into the veins and passes through the blood vessels in the retina. Pictures are then taken to allow the doctor to assess whether the blood vessels are leaking. Different dyes (fluorescein and indocyanine green) are used according to the findings. Another form of angiography can be undertaken on the OCT scanner, often all three tests are undertaken to fully understand the disease activity, and help in optimising treatment.

Find out more about diagnostic tests at The London Clinic Eye Centre.