AGE RELATED MACULAR DEGENERATION
Age Related Macular Degeneration or AMD causes progressive macular damage resulting in loss of central ‘straight ahead’ vision but peripheral vision is not affected. The macula is the central part of the retina, the light sensitive tissue at the back of the eye. The retina processes all visual images and is responsible for our ability to read, recognise faces, drive and see colours clearly. Macular degeneration does not cause pain nor lead to total blindness but may make it difficult or impossible to read or to recognise faces.
Incidence of Age Related Macular Degeneration
Age related macular degeneration is the leading cause of blindness and severe vision loss in older people in Australia. One in seven people over the age of 50 is affected in some way and the incidence increases with age.
Types of Age Related Macular Degeneration
Age related macular degeneration can be classified as early, intermediate and advanced according to the severity. There are also two types of age related macular degeneration.
- Dry Age Related Macular Degeneration results in a gradual loss of central vision and is the most common and less severe form of age related macular degeneration.
- Wet Age Related Macular Degeneration is characterised by a sudden loss of vision. It is caused by abnormal fragile blood vessels growing into the retina, which leak and ooze fluid and blood into the retina. Immediate medical treatment is essential if symptoms occur.
Age related macular degeneration is often a precursor to the wet form. Although 80% of patients with macular degeneration have the dry form, the wet form is responsible for 90% of severe loss of vision associated with macular degeneration.
The primary risk factor for macular degeneration is age, especially age over 50 years. The prevalence and risk of progression increases with age. Other risk factors include family history, female sex and white race. Modifiable risk factors include smoking, obesity, hypertension, dyslipidaemia, excessive sun exposure and a diet deficient in fruits and vegetables.
- Difficulty with reading or any other activity that requires fine vision (e.g. sewing).
- Distortion, where straight lines appear wavy or bent (known as metamorphosia).
- Distinguishing faces becomes a problem.
- Dark patches or empty spaces appear in the centre of your vision.
Source of images: www.retinavitreouscenter.com
The need for increased illumination, sensitivity to glare, decreased night vision and poor colour sensitivity may also indicate that there is something wrong. Any of these symptoms warrant the need for an eye specialist review.
Dry macular degenerative changes usually occur slowly over time. The patient may first notice a need for brighter light when reading. Other symptoms include difficulty adapting to low light levels, increased blurriness of printed words, decreased brightness of colours or a blurred or blind spot in the centre of the visual field.
Visual changes in wet macular degeneration tend to occur rapidly and result in an abrupt decline in central vision. Patients describe distorted images such as wavy lines or notice a distinct blind spot in the centre of their vision.
Early detection of macular degeneration is vital in preserving or saving vision. Difficulty with vision should not be dismissed as a normal part of getting older. In its early stages, macular degeneration can be detected in an eye test before any visual symptoms occur. Early detection allows for treatment to slow its progression.
The Amsler Grid, shown below can be used to test for symptoms of macular degeneration, although this is not to be relied on for a diagnosis. Distortion of the lines (black spot or wavy lines) such as shown in the second image below, warrants an eye specialist review.
Amsler Grid – normal vision
Amsler Grid – visual defects
Treatments for Age Related Macular Degeneration
Treatment options depend on the stage and type of macular degeneration. Current treatments aim to keep the best vision for as long as possible and in some cases may potentially provide visual improvement, but there is presently no cure.
Dry Age Related Macular Degeneration Treatment
Patients with early macular degeneration generally don’t require treatment, but they should have regular eye examinations to monitor disease progression.
Patients with intermediate macular degeneration may benefit from supplements of antioxidants and zinc, which can reduce the risk of progression to advanced macular degeneration.
In patients with advanced macular degeneration in one eye, the risk for progression to advanced disease in the other eye can be reduced by taking antioxidant and zinc supplements.
Age-Related Eye Disease Study (AREDS)
AREDS found that people with intermediate macular degeneration or advanced macular degeneration in one eye only, reduced their risk of advanced Age Related Macular Degeneration by about 25% and associated loss of vision by 19% by taking high levels of antioxidants and zinc. No benefit was shown in those with no or early age related macular degeneration.
The AREDS formula contained vitamin C 500mg, vitamin E 400 IU, beta-carotene 15mg, zinc 80mg and copper 2mg. As beta-carotene has been associated with an increased risk of cancer in smokers, it has been removed from many formulas, including Macu-Vision. This is supported by the Macular Degeneration Foundation.
Macu-Vision needs to be taken TWICE daily to provide the daily dose of vitamin and minerals (minus the beta-carotene) used in AREDS.
Wet Age Related Macular Degeneration Treatment
There are a number of treatments available for wet macular degeneration. They do not cure the disease but aim to stabilise and maintain the best vision for as long as possible. In some cases these treatments can improve vision.
In wet macular degeneration, an excessive growth of blood vessels causes bleeding, leakage and scarring under the retina. This bleeding results in rapid and severe loss of central vision. A protein called Vascular Endothelial Growth Factor (VEGF) is responsible for the development of the blood vessels. To try and block the effect and growth of these blood vessels, anti-VEGF drugs, which act as an antibody, are injected into the eye cavity.
Lucentis is an anti-VEGF drug used to treat wet age related macular degeneration. It is currently the treatment of choice for wet age related macular degeneration in Australia. It is administered as a monthly injection into the eye cavity. The gain in visual acuity is evident at one month and increases for 3 months with vision maintained for two years. Studies showed that 90 to 95% of patients maintained their vision and about 30% had improved vision.
Retaane® (anecortave acetate)
Retaane is indicated for wet age related macular degeneration and works by stopping or slowing down the growth of abnormal blood vessels in the eye. It is administered as an injection under the eyelid using a specially designed needle to access the back of the eye. It is given as a depot injection as a single dose, and may be repeated 6 monthly if indicated.
Visudyne® Photodynamic Therapy (PDT)
PDT is a two-step process where Visudyne (verteporfin) is given via IV infusion followed by light activation in the eye from a cold laser. Several treatments are needed to keep the leaking blood vessels closed and stop the progression of wet age related macular degeneration. It is now rarely used.
Smoking cessation has the most profound effect on risk reduction, as smoking doubles the risk for progression of age related macular degeneration. Maintaining a healthy weight and regular exercise is also recommended.
Prevention: Diet and Supplements
Diet is important in reducing the risk of age related macular degeneration and slowing its progression. In general a healthy diet containing fresh fruits, green leafy vegetables and fish is recommended for eye health. Although eating a balanced diet is the best way to obtain nutrients, the high doses of antioxidants required to slow age related macular degeneration progression is impractical to get from diet alone and supplementation is recommended.
Omega-3 fatty acids are important to eye health. All fish and shellfish contain omega-3s but higher concentrations are found in oily varieties of fish such as salmon, mackerel, anchovies, trout, herring and sardines. If you don’t have 2-3 serves of fish a week, consider an omega-3 supplement.
Foods rich in carotenoids may lower the risk of wet age related macular degeneration. Lutein and zeaxanthin are carotenoids that are present in high concentrations in a healthy macula. Lutein and zeaxanthin are found in particularly high levels in dark green leafy vegetables such as kale, spinach and silver beet. They are present in a range of other vegetables as well such as peas, pumpkin, brussels sprouts, broccoli, corn and beans. If your diet is deficient in fresh fruit and vegetables, consider a supplement.
Bilberry contains anthocyanosides and is marketed to support the health of the retina and improve night vision. While bilberry is a useful antioxidant, there is no evidence that it reduces the risk of age related macular degeneration or slows it progression.
For those with intermediate age related macular degeneration or advanced age related macular degeneration in one eye only, taking an AREDS formula (minus the beta-carotene) such as Macu-Vision twice daily is recommended.
For more information about macular degeneration, visit the Macular Degeneration Foundation. http://www.mdfoundation.com.au/