Age related macular disease

I am sure that you will have heard of this condition, which everybody seems to be talking about these days.
The macula is the central area of the retina.  The retina is like the film in the back of a camera – it collects the visual image, processes it to some extent, and sends it to the brain.  The macula is the area of the retina that is associated with fine detail, and colour vision.  It is used for reading and detail.

AMD is a disease of central vision, affecting the macula.  It is a disease associated with advancing age, and is rarely seen in people under 50. Overall, between 5-15% of the population is affected, albeit most only having a mild form of the disease.  AMD is, however, becoming more common and is currently the leading cause of blindness in the developed world in the over 50-age group.  There are many reasons for this which include:

• Changing dietary habits in the modern world
• We are living longer
• Genetic factors
• Smoking

As the disease develops, aggregations of lipoprotein called drusen, (the waste products of retinal cells) accumulate in the macula.  Initially these may be asymptomatic. As the process advances, the deposits lead to distortion of the macula and hence vision.  Letters and script will start to develop a wobble, letters themselves may become missing.  Vision may start to drop, and it may not be possible to correct this with glasses. These changes are all seen in what is referred to as DRY AMD.

Courtesy Dr Tim Isaacs

These photos show a macula with multiple drusen.

In more severe cases the vision can drop more profoundly, and suddenly.  The central vision may be missing completely.  These changes occur due to new blood vessels growing into the macula.  The vessels leak and bleed, damaging the retinal cells and causing loss of sight.  This is referred to as WET AMD.

Courtesy Chris Barry

This series shows dry AMD changes on the left, a macular haemorrhage in the middle and
subsequent macular scarring on the right.  The vision on the left was 6/9 and subsequently counting fingers on the right.

– Unfortunately you cannot change your genetic makeup or prevent ageing, but scientists are working on altering the genetic code of retinal cells.

• Stop smoking! This increases the risk of progression and chances of developing WET AMD up to six-fold.

• Eat a healthy diet and lose weight – obesity is a risk factor.  In particular, attention should be paid to green leafy vegetables such as broccoli and spinach.  These have a high content of Vitamin A and E as well as trace elements such as copper and zinc and Lutein, all of which are potent antioxidants and beneficial.
• Eating oily fish such as tuna or salmon three times a week is thought to be beneficial.  Fish oil capsules are an alternative.

• If you struggle with a healthy diet, studies suggest that there may be some benefit from taking vitamin supplements such as Macuvision or Luteinvision both, made by Blackmore’s.

Courtesy Dr Tim Isaacs

• Other factors such as hypertension, and high cholesterol levels need to be screened by your GP and treated where necessary.
• Wearing sunglasses protects the macula.

If you have been told that you have AMD, you will need to monitor your vision.  Generally this is best done using an Amsler grid chart.  This can be downloaded and printed from this useful website: http://www.macular.org/pdf/amsler.pdf

This shows distorted vision on an Amsler chart and a pictorial representation of how vision can be affected.

You need to hold the chart at your usual reading distance, with your reading glasses on, whilst fixing one eye on the central dot and covering the other.  If there are any sudden new changes of distortion or your vision rapidly drops you need to see an ophthalmologist as soon as possible – e.g. within 24-48 hrs and not leave it for weeks.

• Fluorescein angiography may be ordered
• An OCT scan of the back of the eye

Up until ten years ago the answer was that, at best, further sight loss could be prevented but sight could not be recovered.  This has all changed with a group of drugs called the anti-VEGF agents.  These are medications that prevent new blood vessels from growing and thus stop WET AMD from progressing.  Studies have shown that not only do they stop the process, but also they actually reverse sight loss in around 90% of patients – as long as they are caught early through screening and monitoring.

These drugs are injected into the eye with a tiny needle.  This sounds scary but in actual fact is very well tolerated by patients.  A local anaesthetic prevents pain.  Unfortunately you will, at least initially, need to have these injections every month.  According to your response the frequency of injections may reduce after about three months.  A newer version of these drugs called VEGF-Trap is now available.  This may offer the potential for increasing the time between injections; thus reducing the frequency of injections.

As the macula deteriorates the visual acuity may drop. There is a large range of disability from minor distortion through to more severe impairment.  Most people have mild/moderate impairment and can maintain this. For some people this may mean that they no longer reach the standards for driving.  Reading may become difficult.  The good news is that your peripheral vision remains intact which means that you can still see to walk about and continue with daily activities.  People with AMD do not go completely blind, where nothing at all is seen.  In my experience this is the most common fear, and when people are told what I have described above, they are much relieved.

If you are registered with the WA Association for the Blind www.guidedogswa.com.au  – this does not necessarily mean you are blind, rather, visually impaired, you may be able to get disability or pension assistance, depending on your circumstances. A home visit can be arranged to see what kind of assistance will help you. Simple measures such as a good illuminating lamp, over your shoulder, will help for reading. The association for the blind can arrange an optometrist’s visit for low visual aid assessment. Magnifiers and other visual aids can be prescribed, often with significant results.

Simple adjustments to household items may assist.  Your medicines can be placed in a Webster pack (compartments arranged by time and day) so that you take the correct medications at the correct time.  This service is offered by most pharmacies.

There are large print books and audio books available in local libraries and commercially.  Many with visual impairment find electronic reading devices such as Kindle and I-pad offer a significant improvement to reading comfort.

Low vision devices range from simple stand magnifying glasses to more sophisticated optical devices including telescopes.  Your home computer can be set up with larger font sizes and higher contrast letters.

Electronic magnifiers and projectors are sometimes helpful with reading bills and important letters.

© 2009 American Academy of Ophthalmology

For further information visit http://www.optelec.com

Retinal implants, connected to the visual cortex of the brain (similar idea to cochlear implants) are currently being developed.  It may be many years before these become generally available and affordable but great strides are being made.

Gene therapy, targeting cells in the retina and surrounding cells, may have a preventative and therapeutic role. It is amazing what science has achieved in our lifetimes.  More amazing is what is around the corner that we have not yet seen or even thought of.  Never lose hope.

A recent study from Australia has shown that the regular use of Aspirin increases the risk of developing the wet form of AMD.  This concurs with other studies from Europe and the USA. This obviously has implications for those who are taking aspirin regularly to prevent cardiovascular complications such as stroke and heart attack.  DO NOT STOP YOUR ASPIRIN.  You should discuss your individual situation with your treating doctors to weigh up the pro’s and cons of such action.  More information will come to light over the coming months.

More information about AMD or assistance can be found at:

http://www.mdfoundation.com.au
http://www.macular.org
http://www.visionaustralia.org.au
www.guidedogswa.com.au
http://www.rcophth.ac.uk/page.asp?section=365&sectionTitle=Information+Booklets
http://www.amdalliance.org