|Last updated: March 2015 |
Suggested citation: Hurley, S, Greenhalgh, EM & Winstanley, MH. 3.10 Eye diseases. In Scollo, MM and Winstanley, MH [editors]. Tobacco in Australia: Facts and issues. Melbourne: Cancer Council Victoria; 2015. Available from http://www.tobaccoinaustralia.org.au/chapter-3-health-effects/3-10-eye-diseases
Cataract and age-related macular degeneration (AMD) are the two leading causes in Australia of vision impairment not correctable by refraction (eye glasses). Cataract is responsible for 37% of such vision loss and AMD is responsible for 26%.1 AMD is responsible for 48% of blindness in Australia and cataract for 12%.1 Smoking increases the risk of both cataract2 and AMD.3, 4 Smoking may also be associated with the rare eye condition Graves' ophthalmopathy, and recent studies suggest a link between smoking and ocular inflammation.
The ocular lens, which is behind the pupil, focuses light onto the retina. It is normally a transparent organ but with age tends to develop opaque areas, which impair vision. These opaque areas are called cataracts.
There are three main types of cataract, classified by their location within the lens structure: nuclear, cortical and posterior subcapsular. Nuclear cataract, which occurs in the centre of the lens, is the most common.5 Each type of cataract has its own distinct risk factors.2 Smoking is a cause of nuclear cataract.2 A study of almost 4000 Australians aged 49 years and older who were followed up for 10 years found that people who had smoked at some time (ever smokers) had a 40% higher risk of developing nuclear cataract than people who had never smoked.5 Although the exact mechanism of causation is not known, many trace metals and other chemicals in cigarette smoke are capable of damaging the proteins in the eyes' lens. Quitting smoking may reduce the risk of developing nuclear cataract and of progression of cataract.2
Smoking may also be associated with an increased risk for developing posterior subcapsular cataract (situated under the external membrane, usually behind the lens) but more research is required.2
The macula is the central area of the retina. It contains the fovea, which is responsible for high-resolution vision. There are two main types of AMD: neovascular (or exudative) and atrophic. The 2014 US Surgeon General’s report concluded that smoking causes both types of AMD.4 A meta-analysis of large studies from the US, Netherlands, Australia, France and Japan also found that the evidence strongly suggests that smoking causes AMD.3 The pooled analysis found a four-fold increase in risk for neovascular AMD and a two- to three-fold increase in the risk of atrophic AMD associated with smoking. A further meta-analysis of studies published up until 2007 confirmed that smoking increases the risk of AMD (neovascular and atrophic combined).6 There are a number of proposed mechanisms for smoking-related damage to retinal structures, primarily oxidative stress; cigarette smoke is a strong oxidant that causes systemic oxidative stress.4 Smoking may also increase oxidative stress on the macula by removing its defences and reducing macular pigment and plasma levels of antioxidants. Inadequate peripheral blood flow might also contribute to the development of AMD.4
The first meta-analysis also found evidence of reversibility, because ex-smokers had a lower risk of AMD. Furthermore, in patients with neovascular AMD who were treated successfully, there was a higher recurrence rate in those who continued smoking compared with those who quit.3 Quitting smoking appears to reduce the risk of AMD, but several decades after quitting smoking, the risk remains higher for former smokers than for never smokers.4
Australian researchers developed a model predicting the decline in risk of AMD after quitting smoking and used it to assess the cost-effectiveness of smoking cessation in relation to AMD. They found that because of the high cost of treating AMD, smoking cessation interventions are cost-effective in terms of their impact on AMD alone (see Section 188.8.131.52).7
Graves' ophthalmopathy is a complication of Graves' disease, a fairly rare autoimmune thyroid disease. The eye complications include protrusion of the eyeballs, double vision, inflammation of eye tissue and damage to the optic nerve. A number of studies have observed an increased risk among smokers for developing the ocular complications of Graves' disease. At this time the evidence is not conclusive, and further research is required.2
Ocular inflammatory disease is inflammation of one or more part of the eye and encompasses uveitis (inflammation of the middle layer of the eye), scleritis (inflammation of the white outer coating) and inflammation of the ocular surface.
Two recent studies have suggested that smoking may be associated with ocular inflammation. One study found that smokers were twice as likely to have uveitis as never smokers.8 The second study found that ocular inflammation was more severe in patients who were smokers and recurred more quickly.9 Cigarette smoke has an inflammatory effect and this may be the mechanism of action.8
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1. Access Economics. Clear insight. The economic impact and cost of vision loss in Australia. Eye Research Australia, 2004. Available from: https://www.cera.org.au/wp-content/uploads/2013/12/CERA_clearinsight_overview.pdf
2. US Department of Health and Human Services. The health consequences of smoking: a report of the Surgeon General. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2004. Available from: http://www.cdc.gov/tobacco/data_statistics/sgr/index.htm
3. Thornton J, Edwards R, Mitchell P, Harrison R, Buchan I and Kelly S. Smoking and age-related macular degeneration: a review of association. Eye 2005;19:935-44. Available from: http://www.ncbi.nlm.nih.gov/pubmed/16151432
4. US Department of Health and Human Services. The health consequences of smoking - 50 years of progress. Atlanta, GA: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2014. Available from: http://www.surgeongeneral.gov/library/reports/50-years-of-progress
5. Tan J, Wang J, Younan C, Cumming R, Rochtchina E and Mitchell P. Smoking and the long-term incidence of cataract: the Blue Mountains Eye Study. Ophthalmic Epidemiology 2008;15(3):155–61. Available from: http://www.informaworld.com/smpp/content~db=all?content=10.1080/09286580701840362
6. Chakravarthy U, Wong TY, Fletcher A, Piault E, Evans C, Zlateva G, et al. Clinical risk factors for age-related macular degeneration: a systematic review and meta-analysis. BMC Ophthalmology 2010;10:31. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21144031
7. Hurley S, Matthews J and Guymer R. Cost-effectiveness of smoking cessation to prevent age-related macular degeneration. Cost Effective Resource Allocation 2008;6(1):18. Available from: http://www.resource-allocation.com/content/pdf/1478-7547-6-18.pdf
8. Lin P, Loh A, Margolis T and Acharya N. Cigarette smoking as a risk factor for uveitis. Ophthalmology 2010;117:585–90. Available from: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=20036011
9. Galor A, Feuer W, Kempen J, Kacmaz R, Liesegang T, Suhler E, et al. Adverse effects of smoking on patients with ocular inflammation. British Journal of Ophthalmology 2010;94(7):848–53. Available from: http://bjo.bmj.com/content/94/7/848.long