Introduction to smoking and eye health
The health conditions most commonly associated with tobacco smoke exposure are cancers and cardiovascular disorders. However, there is now a significant body of evidence showing an increased risk of a number of eye disorders, not only in those who smoke, but also in those who are frequently exposed to tobacco smoke.
What is tobacco smoke?
|obacco smoke is the smoke generated from smoking tobacco. There are two types of tobacco smoke:
While children do not typically smoke cigarettes (at least until adolescence), many are exposed to environmental tobacco smoke, either because their parents smoke at home or in the car, or because they find themselves in environments where adults are smoking. This is commonly known as passive smoking.
Passive smoking has negative effects on the eyes of children exposed to tobacco smoke. The eye diseases and conditions associated with exposure to tobacco smoke in children include:
Allergic conjunctivitis isa condition in which the conjunctiva becomes inflamed due to the presence of an allergen.While no studies have been conducted specifically to assess the relationship between allergic conjunctivitis and tobacco smoke exposure, a number of studies of allergic reactions in children have reported that the risk of developing allergic conjunctivitis increased by about 20% in children who are exposed to environmental tobacco smoke.
In adults, smoking cigarettes is associated with the following eye diseases and disorders:
There is strong evidence that smoking particularly pipe smoking increases the risk of cataracts (clouding of the lens of the eye).A review of 27 studies examining the association between cigarette smoking and cataract reported a 3 times increased risk of nuclear cataract, and also evidence of an association between smoking and subcapsular posterior cataract. While studies have not yet demonstrated an association between environmental tobacco smoke exposure and cataract, it remains a potential risk factor.
For more information on cataracts, including the effect of smoking, exercise and nutrition on eyes, as well as some useful animations and tips to keep eyes healthy, see Cataracts.
Uveitis is a condition characterised by inflammation of the uvea (middle section) of the eye. While no studies have been conducted in humans, laboratory studies using rats have determined that endotoxin (a chemical found in tobacco smoke) can induce an inflammatory response and acute uveitis. Thus it is plausible that tobacco-smoke exposure can increase the risk of uveitis in smokers and those exposed to environmental tobacco smoke.
Smoking is a clearly established risk factor for age related macular degeneration (the deterioration of vision with age). Data from three large cross-sectional studies estimated a 3 times increased risk of age related macular degeneration in smokers compared to nonsmokers.
A review of studies examining the association between age related macular degeneration and smoking reported that smoking actually causes age related macular degeneration, rather than justbeingindirectly associated with the condition. That review also reported that the more people smoked, the more likely they were to develop age related macular degeneration.
The association between environmental tobacco smoke exposure and age related macular degeneration is less clear, and studies to date have presented conflicting results. These conflicting results may be because each of the studies used a different definition of passive smoking.
For more information on age related macular degeneration, including the effect of smoking, exercise and nutrition on eyes, as well as some useful animations and tips to keep eyes healthy, see Macular Degeneration.
Graves’ ophthalmopathy, also called thyroid eye disease,is a condition characterised by inflammation of the eye and fat in the eye socket. Studies have provided strong evidence of an association betweenthyroid eye disease and how much an individual smokes. Smokers with thyroid eye disease had poorer outcomes than nonsmokers. Data suggests that environmental tobacco smoke exposure increases the risk of Graves’ ophthalmopathy, although the data is limited.
Smoking has been linked to an increase in disorders of the eye’s ocular surface which result in symptoms such as itchness, redness and irritation of the eyes. Changes to the eye’s ocular surface associated with smoking include changes to the lipid layer of the tear film, reduced tear secretion and reduced corneal and conjunctival sensitivity. Passive smoking can also increase the risk of these disorders. Ocular surface disorders include atopic keratoconjunctivitisand allergic conjunctivitis.
Reducing or eliminating exposure to environmental tobacco smoke and stopping smoking are the key ways to prevent tobacco smoke associated eye disorders.