Macular Degeneration

The Role of Drusen

Age related macular degeneration is a condition which affects the retina of the eye resulting in impairment of the central vision. It is the leading cause of blindness in Australia. The macula is at the centre of the retina and is responsible for detailed, central vision. Gradually only peripheral vision is left with victims unable to read, drive or recognise faces.

Macular degeneration (MD) occurs when waste products build up beneath the layer of cells (the retinal pigment epithelium [RPE]) underneath the retina. These waste products are normally removed in blood vessels known as choroids. If the waste products are not removed, they form deposits known as ‘drusen’.

Drusen appear as yellow or white spots. These are easily spotted by an eye specialist at an eye examination. Drusen are formed of deposits of lipids (a fatty compound) and calcium.

Being diagnosed with drusen does not mean you have macular degeneration, although drusen can be an early sign of age-related MD. Drusen may not become full-blown MD. Many older people may develop one or two drusen but never experience any further problems.

Drusen can cause the retinal pigment epithelium (RPE) to die, in which case the MD is known as ‘dry’. On the other hand, if the drusen attracts blood vessels from the choroid, the outcome is the onset of ‘wet’ MD.

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The two main types of drusen are hard and soft with each type having a different prognosis.

Hard drusen are the less harmful form. They are very common with age and are quite small, round in shape with distinct, well defined borders. They are common in people over the age or 40 but are not an indication of developing MD. However they may develop into the soft kind.

The soft drusen is considered an early indicator of MD although having soft drusen does not always lead to MD. Soft drusen are pale yellow with ill-defined borders. They are larger than the hard type and vary in size and shape. Soft drusen are more often associated with loss of vision and may cause the RPE to separate from the other retinal layers.

They are sometimes treated with a very gentle laser treatment. This is done in the hope of causing the drusen to regress or disappear. It is an attempt to delay loss of vision as over time there will be some loss of sight. Because the long term effects are not known, only one eye is treated. Such a procedure is not without risk and should be discussed fully with your doctor and/or eye specialist.