Macular Degeneration

/Macular Degeneration
Macular Degeneration 2018-06-28T07:02:59+00:00

What is Macular Degeneration

Macular degeneration (MD) is the leading cause of blindness and severe vision loss in Australia. It causes destruction of cells at the area of the retina that is responsible for providing detailed central vision. The macula has the highest concentration of photoreceptor cells in the retina and can be thought of like the fingertip of your eye, in that it has the finest visual sensitivity. However, the macular also has an achilles heel, because the high concentration of photoreceptors required for providing detailed vision also leads to a high production of natural cell waste products that can build up over time leading to a loss of normal function. MD doesn’t normally affect people below the age of 50, but from this age the incidence of risk increases with age and by the age of 80 around 30% will have some form of MD. The progression of MD varies, and while in some it changes gradually over time with minor effect on vision, in others it can progress rapidly with more severe effects. Although MD cannot be cured, in many cases it can be treated to slow progression, so early detection is vital. Fortunately it is now much easier to detect MD with new imaging techniques like Optical Coherence Tomography (OCT). Treatment of MD is also constantly evolving leading to better outcomes when detection is made early, and ongoing research is revealing new ways to reduce the likelihood of developing MD.

Macula location

Macula location

Normal vision

Normal vision

Loss of central vision from Macular Degeneration

Loss of central vision from Macular Degeneration

Risk Factors

MD is an age related condition that affects one in seven people over the age of fifty. However some people are at higher risk of developing MD:

  • Family history increases the risk of developing MD to 50%
  • Smokers, and those with a history of smoking, are three times more likely to develop MD, with likelihood of developing MD occurring 10 years earlier
  • Increased UV exposure, such as a history of working outdoors without UV blocking sunglasses
  • Diets with a high intake of saturated fats, trans-fats and salt

 

Reducing The Risk

Genetics cannot be changed and aging is a fact of life, but there are some steps that you can take to reduce the risk of developing MD, or help slow progression of MD.

  • Increase your intake of green leafy vegetables and fish and limit intake of fats
  • Follow a low glycemic index diet
  • Regularly check blood pressure and cholesterol with your GP
  • Maintain a healthy weight
  • Quit smoking
  • Participate in regular exercise
  • Wear UV protecting eyewear and sunglasses, starting from childhood

Any changes to diet or lifestyle should be undertaken in consultation with your doctor.

Macular Degeneration Foundation Australia offer an excellent nutrition guide that can be downloaded from their website.

Regular eye examinations won’t reduce the risk of developing MD, but they are a vital step in early detection of the disease.

People at risk of developing MD should regularly view an Amsler Grid, that can be downloaded from Macular Degeneration Foundation Australia by clicking this link, to test for early changes to the health of their macula.

 

Symptoms

In its early stages, macular degeneration may not have symptoms and may be unrecognized until it progresses or affects both eyes.
Symptoms of macular degeneration include:

  • Straight lines start to appear distorted, or the center of vision becomes distorted
  • Dark, blurry areas or white out zones appears in the center of vision
  • Difficulty with reading or any other activity that requires fine vision
  • Problems distinguishing faces

Many people initially experience the need for increased illumination, along with sensitivity to glare, decreased night vision, and problems with colour sensitivity.

 

Types Of Macular Degeneration

The retina is the light-sensitive tissue that lines the inside of the eye and is responsible for detecting light. That light detection is then sent as a signal through the optic nerve and into the brain for processing of the image. There are ten distinct layers to the human retina that lie flat on top of each other like layers on a cake. The picture below under Optical Coherence Tomography (OCT) shows a scan cross-section of the layers of the retina in a healthy eye. The dip in the centre of the scan is the macula. There are two forms of macular degeneration – the dry form and the wet form.

Dry Macular Degeneration:

The dry form of macular degeneration is the more common type, accounting for about 90% of all cases of MD. The dry form is the result of the cells in the retina slowly breaking down and degenerating to the point that they lose their normal function and cause a disruption in vision. This is the slow-progressing form of MD.

Wet Macular Degeneration:

The wet form of macular degeneration occurs in about 10% of patients that have MD. In this type of MD, fragile blood vessels grow underneath the macula and leak fluid causing haemorrhages and swelling at the macula and can be likened to bruising on the retina. This fluid leakage can happen quite quickly and lead to a sudden loss of vision disruption.

Normal retina

Normal retina

Dry Macular degeneration

Dry Macular degeneration

Wet Macular Degeneration

Wet Macular Degeneration

Detecting Macular Degeneration

Regular eye examinations won’t prevent your chance of developing MD, but early detection is vital in slowing progression.

During a full eye examination your optometrist will directly assess your macula using an ophthalmoscope and take a digital retinal image (DRI). If these tests raise any concern, or for people in MD risk categories (including being over 50), we will recommend OCT which provides a three-dimensional highly magnified cross section image of the macula.

Our optometrists will always check the health of your macula during a full eye examination, but if you want extra assurance or more advanced macular imaging to be performed, please advise your optometrist at the start of the examination and they will describe the full options that are available to you at GJO.

Digitial Retinal Imaging (DRI)

At GJO we capture a digital image of the retina including the macula, optic nerve head, and surrounding blood vessels. Digital retinal imaging provides a detailed image of the macular surface that can be magnified using our modern imaging technology, but just as importantly it provides a permanent record that can be used to assess for changes over time. The best detection for early signs of MD is to be able to compare back to previously captured images.

Optical Coherence Tomography (OCT)

The OCT scan is a brand new technology that allows us to measure retinal and macular thickness through high resolution imaging. It has quickly become the gold standard for assessing risk of macular degeneration and is essentially like taking an MRI through the layers of the retina to give our optometrists more detailed information about the retina to help early detection of macular generation. The OCT at GJO utilises cutting edge technology to capture multiple scans through the macula and then each of these images can be enlarged to provide a detailed analysis of the macula structure. In the OCT image of the normal eye below the retinal structure is smooth and looks like the layers of a cake. The scan on the right was taken at GJO on a patient who was unaware that they had early MD and instead shows bumpy retinal layers which are clearly different to the scan of the normal retina to the left.

OCT of healthy macula

OCT of a healthy macula – this shows the several layers of the retina in cross-section, with the central dip being the macula

OCT of an eye with early dry Macular Degeneration

OCT of an eye with early dry Macular Degeneration

In addition to providing a detailed cross-section of the retina and macula our OCT instrument also performs several age-matched analyses to help determine if any early changes due to macular degeneration are present. The coloured pie-chart shown in the picture below gives an age-matched analysis of macular thickness. If the sections of the pie-chart are coloured outside of the normal ‘green’ range, as in the image below, then we know there are abnormal changes occurring at the macula that need to monitored closely or refered to a specialist for medical treatment.

OCT_diagnostic

Treatments

The early detection of any form of MD is crucial because the earlier that treatment is inititated the more likelihood there is of slowing any further progression. MD can cause many different symptoms so it is important that any difficulty with your vision is discussed with your Optometrist and not just dismissed as part of getting older. In its early stages MD may not be noticed but it can be detected in an eye examination before any visual symptoms occur. There are several treatment options available depending on the type and severity of the MD, and we work closely with Ophthalmologists (eye surgeons) to ensure you can access these treatments as soon as may be required. Regular eye examinations are crucial to maintaining the health of your eyes.

 

Additional Resources

Macular degeneration foundation – www.mdfoundation.com.au
Retina Australia – www.retinaaustralia.com.au/md.htm
Fred Hollows Foundation – www.hollows.org.au/eye-health/macular-degeneration