The smoking ban in public places in England starts on the 1st July and is part of a government initiative to reduce smoking related diseases. These include respiratory, vascular and malignant conditions.
As optometrists, will we see any clinical effect from the ban?
Smoking has clearly been linked to cataracts. Studies have shown that smokers have up to a three-fold increase of developing nuclear sclerosis. Although potentially devastating to patients in developing countries where medical treatment is not so readily available, due to the advances in cataract surgery, many people in the western world with nuclear sclerosis undergo surgery and any degradation to the vision is eliminated.
Macular degeneration, affecting 700,000 people in the UK in 2004, has many fewer treatment options and so prevention of the condition is more important. Its prevalence is expected to increase by 31% by the year 2020. Studies have linked smoking to advanced macular degeneration, classified as choroidal neovascularization (formation of blood vessels in the sub retinal space) and geographic atrophy (extensive loss of the retinal pigment epithelium and choriocapillaris). Drusen are signs of early macular degeneration but there is no certainty that the presence of drusen leads to the formation of the more advanced stages of macular degeneration.
Three theories can describe the aetiology of macular degeneration:
1. Vascular theory
2. Oxidative Stress theory
3. Degradation of Bruch’s Membrane
Smoking is believed to cause macular degeneration by the oxidative stress theory, where normal metabolic processes in the retina produce free radicals by oxidation. These can be molecules such as superoxide, hydrogen peroxide, hydroxyl radicals and single oxygen radicals.
Lipid peroxidation can be initiated by these free radicals leading to intercellular damage of proteins carbohydrates and DNA. The retina is especially susceptible due to an abundance of fatty acids in the macular region, the retina being subjected to high levels of light exposure causing the formation, phagocytosis produces free radicals (during the renewal of the photoreceptors at the level of Bruch’s membrane) and also due to the high metabolic activity found in the retina.
Recent research agrees that smoking increases the risk of advanced macular degeneration, however no evidence liking smoking to an increase in early AMD drusen) was seen. The EUREYE study shows a five-fold increase in geographic atrophy and 2.5-fold increase in neovascular AMD in current smokers compared to non-smokers however other studies show these figures to be slightly lower, but the association still significant. Giving up smoking shows a reduction in the risk factor, with patients who have given up smoking for at least twenty years having nearly the same probability as non-smokers to developing AMD. If cessation has been for less than twenty years then they are approximately twice as likely to develop advanced AMD.