Macular Degeneration

Macular degeneration is a common eye condition that refers to the deterioration of the macula, the important central part of the retina in the back of the eye (see diagram). Although there are rare forms of macular degeneration that can occur in young people (usually called macular dystrophy), it is rare to develop macular degeneration before 60 years of age. Most cases of macular degeneration are age-related (AMD). The result of AMD is reduced sight in the centre of the field of vision. Macular degeneration is the commonest cause of visual impairment and blindness in adults in developed countries.

 

Macular-Degeneration

Macular Degeneration

 

The main risk factors for developing AMD, apart from age, are family history and smoking. Minor risk factors include high blood pressure, elevated cholesterol, obesity, intake of certain dietary fats, and excessive exposure of the eyes to sunlight over your lifetime.

 

Dry Macular Degeneration

Generally, AMD develops slowly over many years as the light-sensitive cells, the rods and cones, in the macula start to wear out with age. Rods and cones are continually being broken down and then recycled in an ongoing dynamic process. With advancing age, the rods and cones are not recycled as efficiently, and breakdown products start to clump together under the retina forming drusen. These drusen, along with loss of the pigment layer that is under the retina, are the hallmarks of dry macular degeneration, which accounts for 90% of all cases of AMD.

 

The symptoms of dry AMD include:

 

  • Mild blurring of the vision when reading or watching TV
  • Difficulty focusing on small objects up close or street signs in the distance
  • Difficulty making out peoples’ faces clearly
  • Dark circles in the central vision when you first wake up in the morning
  • Needing more light or stronger reading glasses to read small print.

 

You may also find it more difficult to tell the difference between certain colours, and it may take longer to adjust when you go from the dark into bright sunlight, and vice versa.

 

Diagnosis of dry AMD by your eye surgeon is simply a matter of examining the back of your eyes with a slit lamp (a microscope used by eye care professionals) and special lenses. Your pupils will be dilated for this examination. Other tests performed at the same time will include measuring your visual acuity, testing your glasses prescription, and examining for the presence of other eye diseases such as cataract and glaucoma. Sometimes photographs or an ultrasound of the back of the eye may also be taken, but more extensive or invasive testing is not required.

 

Treatment of dry AMD involves reducing the factors that predispose you to it, modification of your diet, and vitamin supplements. This may include some or all of the following:

 

  • Stopping smoking
  • Wearing sunglasses and a hat outdoors
  • Eating a diet high in green and yellow fruit and vegetables
  • Eating fish rather than red meat as a source of protein in your diet
  • Adding more nuts to your diet (especially brazil nuts and walnuts)
  • Avoiding canola oil and margarine containing canola oil
  • Taking antioxidant vitamins – particularly vitamin C and vitamin E
  • Taking supplements containing lutein and zeaxanthin
  • Taking fish oil
  • Better control of your blood pressure
  • Taking medication to lower cholesterol

 

There are many formulations of vitamins and dietary supplements that have been developed for treating dry AMD, based on large population studies performed over many years. These are available from the pharmacy without prescription. Your eye specialist may also suggest the best supplement for you.

 

Dry AMD progresses at very variable rates in different people. With careful attention to the above treatments, you may preserve normal vision for the rest of your life. In other people, despite appropriate care, dry AMD can progress to the advanced stages known as geographic atrophy. When this occurs, the central vision can fade completely, which will mean you will no longer be able to drive a car or read a book. The good news about advanced forms of AMD is that your peripheral vision will always be preserved, and most people with advanced dry AMD can live independently and care for themselves.

 

Wet Macular Degeneration

Wet AMD is the less common, but more severe, form of the disease. It will develop in about 10% of people with macular degeneration, and usually develops after dry AMD has been present for some years. It can progress very quickly and the central vision can be permanently lost if this condition is not diagnosed and treated promptly.

 

Wet AMD occurs when blood vessels from beneath the retina grow through weak spots under the macula. These blood vessels then leak fluid that swells the macula, causing distortion of the central vision. These blood vessels may also bleed. If untreated, scar tissue will form causing permanent damage and loss of vision.

 

The symptoms of wet AMD include those mentioned above for dry AMD, with the important addition of distortion of objects in the central vision. Straight lines may look wavy or bent. An Amsler grid can be used at home to test for wet AMD. Particularly if you already have dry AMD, it is useful to use an Amsler grid to help early detection of wet AMD. Amsler grids are available from Visionary Eye Specialists.

 

For treatment of wet AMD, a test called a fluorescein angiogram may be performed to determine how best to treat the problem. A number of treatments for wet AMD have been developed over the years including laser, external beam radiation, corticosteroid injections, and photodynamic therapy. These are all effective to some degree, but they have almost exclusively been replaced by a group of medicines called anti-vascular endothelial growth factors (anti-VEGFs). Anti-VEGFs are given by injection directly into the eye where they inhibit the growth of the abnormal blood vessels. They are effective at stabilising the vision in most cases, and in some cases, they improve the vision to some degree. The main downside of this therapy is that injections need to initially be given every 4 weeks to maintain the effect. In some cases, the time between injections can be extended to every 6–12 weeks but it is rare to not need ongoing injections to control wet AMD once it is diagnosed, even after a number of years.

 

Illustrations shown are provided courtesy of the Royal Australian and New Zealand College of Ophthalmologists (RANZCO) and Mi-Tec Publishing. The complete RANZCO patient education pamphlet is available from your ophthalmologist