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Australian Journal of Pharmacy : November 2006
pharmacy ed current drug information Dr Jack Thomas, consultant editor Macular degeneration, fat and smoking M ACULAR degeneration is a medical condition in which the light sensing cells in the macula malfunction and, over time, cease to work. It is the leading cause of central vision loss (blindness) for those older than 50 years. There are two basic types of the disease: standard macular degeneration (MD), sometimes called juvenile macular degeneration (JMD), and age-related macular degeneration (ARMD), with ARMD being the most common form of the condition. In macular degeneration the final form results in missing or blurred vision in the central, reading part of vision. The outer, peripheral part of the vision remains intact. ARMD is further divided into a ‘dry,’ or nonexudative, form and a ‘wet,’ or exudative, form. Eighty-five to 90 per cent of cases are categorised as ‘dry’ macular degeneration where fatty tissue, known as drusen, will slowly build up behind the retina. Ten to 15 per cent of cases involve the growth of abnormal blood vessels under the retina. These cases are called ‘wet’ macular degeneration due to the leakage of blood and other fluid from behind the retina into the eye. Wet macular degeneration usually begins as the dry form. If allowed to continue without treatment it will completely destroy the macula. Risk factors Ageing: About 10 per cent of patients aged 66 to 74 years will have findings of macular degeneration. The prevalence increases to 30 per cent in patients aged 75 to 85 years. Smoking: The only environmental exposure clearly associated with macular degeneration is tobacco smoking. Family history: There is a four-fold lifetime higher risk of developing late-stage macular degeneration for people who have a relative with macular degeneration as compared with those who do not. Other risk factors are considered to include macular degeneration gene, hypertension, cardiovascular risk factors (high cholesterol, obesity), high fat intake, oxidative stress, race (more likely to be found in whites than in blacks), and exposure to sunlight, especially blue light. Two studies have been carried out to evaluate modifiable risk and protective factors for age-related macular degeneration (AMD) among elderly subjects.1 In one study, 681 elderly male twins from the National Academy of Sciences—National Research Council World War II Veteran Twin Registry were involved in the environmental component of the study. To determine genetic and environmental risk factors for AMD, twins were surveyed for a prior diagnosis of AMD and 76 ? THE AUSTRALIAN JOURNAL OF PHARMACY, VOL.87 NOVEMBER 2006 ...cigarette smoking increases risk while fish consumption and omega-3 fatty acid intake reduce risk of AMD underwent an eye examination, fundus photography, and food frequency and risk factor questionnaires. It was found that 222 twins had AMD (intermediate or late stages) and 459 twins had no maculopathy or early signs of AMD. Risk for AMD according to cigarette smoking and dietary fat intake was estimated using appropriate statistical analyses. The results obtained showed that: • current smokers had a 1.9-fold increased risk of AMD; • past smokers had about a 1.7-fold increased risk; • increased intake of fish reduced risk of AMD, particularly for two or more servings per week; and • dietary omega-3 fatty intake was inversely associated with AMD comparing the highest versus lowest quartile. It was calculated that the risk percentage was 32 per cent for smoking and the preventive fraction was 22 per cent for higher omega-3 intake.