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Smoking and Eye Disease
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Action on Smoking and Health – September 2005 |
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Tobacco smoke is composed of as many as 4,000 active compounds, most of them toxic and potentially damaging to the eye. Smoking can cause or worsen several eye disorders, particularly cataract and Age-related Macular Degeneration (AMD), and may lead to blindness.
Benefits of stopping smoking Stopping smoking can halt or reverse damage to the eyes, depending on the severity and type of disease. In the case of AMD, former smokers have only a slightly increased risk compared with never smokers. [1] Stopping smoking reduces the risk of developing cataracts. A US study found that, compared with men who continued to smoke, those who had quit 10 years or less before study entry had an approximately 20% reduced risk of cataract diagnosis. [2]
Cataract Cataract is a loss of transparency in the lens of the eye. Untreated cataract will lead to loss of vision. Cataracts can develop as part of the normal ageing process but may, in part, be preventable. Smoking is a major risk factor.[3] A review of the evidence revealed that smoking increases the risk of a particular type of cataract - nuclear cataract. Compared with never smokers, smokers of 20 or more cigarettes per day are at least twice as likely to develop cataract.[4] A smoker’s risk of cataract increases with the amount smoked and cataracts are more serious in heavy smokers than in light smokers.
Although the exact mechanism by which smoking causes cataracts to develop is not fully understood, it is probable that the destruction of antioxidant nutrients by tobacco smoke is a leading contender. Antioxidants help maintain lens transparency. Cigarette smoking may also breakdown other micronutrients critical to healthy eye tissues. 3
Age-Related Macular Degeneration (AMD) Age related macular degeneration (AMD) affects the macula, the small central area of the retina at the back of the eye which is responsible for clear, central vision. If the macula is affected, vision becomes blurred, distorted and dark in the centre (this is called a scotoma). Although peripheral vision is not affected by AMD, loss of central vision means that every day activities such as reading, driving and watching television cannot be performed. AMD is the leading cause of blindness in people over the age of 55 in the western world.
Smoking is the major preventable risk factor for AMD. Smokers are more likely to suffer from all types of AMD and relapses after laser treatment are more likely in smokers. If detected in time, treatment for some forms of AMD can reduce or delay sight loss. Evidence from large population-based studies has shown that smoking more than doubles the risk of developing AMD. [5] A review of 17 studies found an increased risk of AMD of two- to three-fold in current smokers compared with never smokers. [6] It is estimated that smoking may account for more than 40,000 cases of AMD with sight loss in people aged 70 and over in the UK, including ex-smokers, and up to 28,000 among current smokers. [7] [8]
Smoking and Diabetic Retinopathy Smoking may accelerate the development of, or worsen diabetic retinopathy, an eye complication associated with diabetes. In this disease, which can lead to blindness, the blood vessels that supply the retina are damaged by high blood sugar levels. When these blood vessels become damaged, they may leak fluid or blood and grow scar tissue which can distort the images the retina sends to the brain. Smoking may worsen this condition further because smoking also damages blood vessels. A possible mechanism leading to damage of the retina is smoking-induced hypoxia. This condition is a result of diminished oxygen in the blood, with a corresponding increase in carbon monoxide. 3 For further information about smoking and diabetes see ASH Factsheet, Smoking and Diabetes .
Thyroid Eye Disease In Graves’ disease, the thyroid gland becomes overactive, secreting too much thyroid hormone. An eye disorder known as thyroid eye disease is a most serious complication. Protrusion of the eyes, double vision, and loss of vision, sometimes causing blindness can occur. People with Graves’ disease who smoke have a four-fold increased risk of developing these eye complications compared to non-smokers.[9] Smokers also have a higher risk of the more advanced eye problems and the risk is elevated in heavy smokers. The reason for smokers’ increased risk of eye disorders in this condition is not fully understood but it is believed to be due to a smoking-induced impairment of the immune system. 3
Optic Neuropathy Anterior ischaemic optic neuropathy is an eye disease that results in a sudden, painless loss of vision, often leading to permanent blindness. It occurs because of reduced blood flow in the arteries to the eyes. Atherosclerosis – clogging of the arteries – may be responsible for this disease. Smokers are at a 16-fold increased risk of developing this disease compared with non-smokers. Furthermore, smokers develop optic neuropathy at younger ages: in one study smokers were found to develop the disease at an average age of 51 and nonsmokers at an average age of 64. 3
Passive smoking and eye disease Nonsmokers often complain of eye irritation when exposed to tobacco smoke. There is currently little evidence about the risks of passive smoking for eye disease. One major study found that passive smoking was associated with increased risk of late AMD although the association was not statistically significant. [10] Children born to women who smoke during pregnancy are prone to developing strabismus (squinting). [11] Experience from other conditions suggests that passive smoking causes the same diseases as active smoking but at a reduced risk.[12]
Education campaigns Public awareness about the risk of eye diseases associated with smoking is very low. According to one recent poll, only seven percent of people knew that AMD could affect the eyes. However, seven out of ten smokers say they would either stop or reduce consumption if they thought smoking could harm their eyesight. [13]
Mass media campaigns in Australia and New Zealand have been very successful in raising awareness about the risk of eye diseases associated with smoking. In 2000, the Australian National Quit campaign ran an advertisement as part of a series entitled "Every cigarette is doing you damage" which explicitly addressed AMD. [14] In 2006 the Australian government will require new mandatory pictorial pack warnings, one of which will be about AMD. This warning was one of those having the greatest impact among smokers in the research conducted for the government prior to the announcement. [15]
As part of the European Tobacco Products Directive, the European Commission has issued a proposal to enable member states to introduce pictorial health warnings on tobacco packaging. However, these images do not currently include a proposal to include warnings about smoking and blindness. The AMD Alliance International and partners - the Royal National Institute for the Blind, the British Medical Association and the Royal College of Ophthalmologists - are campaigning for warnings about AMD to be included on tobacco packaging and for smoking and blindness to be included as part of the EU-wide ‘HELP for a life without tobacco’ mass media campaign. 13
North West ASH has produced a large print leaflet on smoking and blindness, including tips on stopping smoking. Contact NWASH on: 0161 762 3166. email: info@nwash.co.uk A pdf is also available on the website:. www.nwash.co.uk A large print version of this factsheet is also available at: http://www.ash.org.uk/html/factsheets/html/fact27largeprint.html |
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References
[1] Smith, W et al. Risk factors for age-related macular degeneration. Pooled findings from three continents. Ophthalmology 2001;108: 697-704
[2] Christen,WG et al. Smoking cessation and risk of age-related cataract in men. JAMA 2000; 284 (6): 713-716 View abstract
[3]Cigarettes: What the warning label doesn’t tell you. (Chapter 15: Smoking and the eyes.) American Council on Science and Health. New York ACSH, 1996
[4] Kelly,S et al. Smoking and cataract: a review of causal association. Journal of Cataract & Refractive Surgery. (In press)
[5] Tomany,SC, et al. Risk factors for incident age-related macular degeneration. Pooled findings from 3 continents. Ophthalmology 2004; 111:1280–7. View abstract
[6] Thornton,J et al Smoking and age-related macular degeneration: a review of association. Eye 2005; 19: 935-944 View abstract
[7] Edwards,R et al. Age-related macular degeneration in the United Kingdom: estimates of smoking-related vision loss. Letter. Br J Ophthalmology 20 July 2005 View letter
[8] Evans,JR, Fletcher, AE and Wormald, RPL. 28,000 cases of age related macular degeneration causing visual loss in people aged 75 years and above in the United Kingdom may be attributable to smoking. British Journal of Ophthalmology 2005; 89: 550-553
[9] Hegedius,,HL, Brix,TH and Vestergaard,P. Relationship between cigarette smoking and Graves’ ophthalmopathy. J Endocrinol Invest. 2004; 27(3): 265-271
[10] Smith W, Mitchell P and Leeder SR. Smoking and age-related maculopathy. The Blue Mountains Eye Study. Archives of Ophthalmology 1996; 114: 1518-1523.
[11] Solberg Y, Rosner, M and Belkin, M. The association between cigarette smoking and ocular diseases. Surv Ophthalmol 1998; 42(6): 535-47
[12] Going smoke free. The medical case for clean air in the home, at work and in public places. A report of the Tobacco Advisory Group of the Royal College of Physicians. London, RCP, 2005
[13] Awareness of age-related macular degeneration and associated risk factors. AMD Alliance International: Campaign Report, 2005 AMD website and report
[14] Chapman, S. Cigarette pack warning: it can send you blind! Br J Ophthalmology 7 June 2005 View letter
[15] Information relating to
proposed pictorial health warnings in Australia. : View report