What is Macular Degeneration?
The retina is a thin tissue at the back of the eye, which works like a film in a camera. The word ‘macula’ refers to center of the retina. Being central, macula provides detailed sharp vision. A healthy macula is especially vital to performing near vision tasks such as reading or knitting. The word ‘degeneration’ means wear and tear. So when the macula suffers from wear and tear the resulting condition is called Macular Degeneration.
What causes Macular degeneration?
The exact cause is not known but cells in the macula break down due to the aging process, hence the term Age-Related Macular Degeneration (ARMD). Family history of ARMD and smoking tobacco are the known important risk factors. Less commonly, macular degeneration can occur in severely shortsighted people (high myopia) or in people with certain inflammatory and genetic conditions.
What are the symptoms?
There are no symptoms in the initial stages but assessment of the macula can reveal drusens, tiny yellowish deposits caused by the failure of the macula to get rid of its waste products. As the condition progresses, drusens increase in number and enlarge in size (Figure: 1).
As the macular cells begin to disintegrate symptoms of blurred vision become noticeable. This especially affects the ability of people to see what is directly in front of them. Reading, writing and close work such as knitting is affected the most. As the disease progresses, people experience significant vision loss in the center and are unable to recognise faces. The peripheral retina is never affected. Therefore, people never experience complete loss of vision as peripheral/side vision remains intact.
What are the ‘Dry’ and ‘Wet’ types of macular degeneration?
Dry and Wet ARMD are two stages of the same disease. ARMD begins as the Dry type, progresses over decades, with approximately 10% of the patients developing Wet ARMD. In Wet ARMD, there is a growth of leaky blood vessels that waterlog the Macula with fluid and/or blood. This can lead to a rapid decline in their vision. So, Wet ARMD is not a type but a specific abnormality that develops in patients with ARMD. In Dry macular degeneration, the light-sensitive cells in the macula slowly break down, leading to gradual blurring of the central vision. As it gets worse, the macula becomes increasingly thin and the central blurred patch increases. Figure 2 shows significant loss of macular tissue due to advanced Dry ARMD.
In the Wet form of macular degeneration, patients develop fragile and leaky blood vessels. This leads to leakage of fluid and blood in the macula hence the term ‘Wet’. If untreated, it leads to permanent damage to the macula and formation of a scar. Wet macular degeneration can happen suddenly leading to rapid loss of sight. Figure 3 shows haemorrhage in the macula due to Wet ARMD.
Why is it important to differentiate between dry and wet form?
Patients with wet ARMD require prompt treatment. Delay in treatment can cause rapid decline and irreversible loss of central vision. Patients with dry ARMD, on the other hand, require assessment, advice and regular checks.
How is the diagnosis made?
Specialized photographs of the macula are taken to confirm the type of macular degeneration and to decide the appropriate treatment course.
1. Fundus fluorescein angiography – in this test, a dye is injected in the arm and photographs are taken of the dye as it passes through the blood vessels at the back of the eye. Figure 4 shows vascular membrane growing under the macula, which indicates Wet ARMD.
2. OCT retinal scan – It is a simple test which uses a light beam to build up a detailed picture of the macula. In Wet ARMD there is collection of fluid under as well as within the macula as seen in figure 5.
What is the treatment for Dry macular degeneration?
Unfortunately, there is no treatment or cure for dry ARMD. Giving up smoking reduces the risk of severe sight loss by 30%. Wearing sunglasses to protect the eyes from sun’s rays and eating a healthy diet rich in antioxidants such as green leafy vegetables and citrus fruits may be beneficial. Age Related Eye Disease Study 2 (AREDS 2) showed that supplements containing Vitamins C (500 mg), Vitamin E (400 IU), Lutein (10 mg), Zeaxanthin (2 mg) and Zinc (80 mg) taken daily may benefit in slowing down the disease but it does not prevent ARMD from advancing. These supplements can be purchased from health shops or pharmacies. Smokers or ex-smokers should avoid any supplements containing Beta Carotene due to risk of lung cancer.
What regular assessments are required for Dry macular degeneration?
Mr Patwardhan offers regular assessments and OCT scans to patients with Dry macular degeneration. These assessments are often vital in diagnosing Wet ARMD at an early stage, and prompt intervention in these cases can prevent significant vision loss. Please contact Mr Patwardhan’s secretary to make an appointment for assessment.
What is the treatment for Wet macular degeneration?
Wet macular degeneration is treated by injection of anti-vascular endothelial growth factor (anti-VEGF) drug in the eye. Lucentis, Eylea and Avastin are the drugs available in this category. Anti-VEGF drugs work on leaky blood vessels to help reduce fluid in the macula. These drugs are injected into vitreous humour (gel at the back of the eye) under local anaesthesia.
What is the difference between the drugs?
All three belong to the same family of drugs called anti-VEGF. All three work equally well and have similar risks attached to it. However, the use of Avastin is considered unlicensed when used for macular conditions. This is because Avastin is licensed for use as intravenous injection to treat certain cancers. When a fraction of the drug is used as an injection into the eye it produces the same effect as the licensed anti-VEGF drugs. Two global trials (CATT and IVAN) have proven that Avastin is as effective and as safe as Lucentis. The main difference is that Lucentis and Eylea are supplied in company-packaged vials and Avastin is prepared by local pharmacies and supplied in small syringes. The way Avastin is prepared may potentially increase the risk of contamination. To minimize this risk, the hospital sources Avastin from very reliable pharmacies in the UK.
How is the treatment given?
The Anti-VEGF drug is injected into the eye under local anaesthesia. You will receive monthly injections for the first 3 months. After 3 months, injections are given as and when necessary in the case of Lucentis and Avastin. In the case of Eylea injections are given every 2 months from then on. At every visit you will require an eye assessment and an OCT scan to assess the response. How many injections are needed depends upon how aggressive the disease is. Patients with a more aggressive form of Wet AMD will need more frequent injections.
What are the benefits and risks involved?
With regular assessment and treatment, approximately 90% of patients will experience success in preventing vision loss and almost 30% of patients will notice sustained improvement in their vision at the end of two years. The treatment does not cure the condition, but, prevents rapid loss of vision. The injection carries a small risk (0.3%) of sight-threatening infection, endophthalmitis. There is a small risk of developing glaucoma (increased pressure in the eye) or cataract (cloudy lens). With frequent injections there is a small risk (1-2%) of cardiovascular events such as heart attack and stroke.