Smoking and Eye DamageMacular degeneration is the result of damage inside the eye that can lead to irreversible blindness. It can occur in one or both eyes and cause a permanent ‘blind spot’ directly in the line of sight. Macular degeneration is the leading cause of blindness in Australia and affects people over the age of fifty. It has a direct effect on peoples’ daily lives, severely limiting their ability to carry out everyday tasks such as driving, reading, writing or even recognising faces.
Smoking can cause damage to the macula (the part of the retina at the back of the eye that we use when we look directly at someone or when reading). It may also constrict blood vessels to this area. There are two types of macular degeneration. In the first, critical parts of the macula may die (atrophy) or, in the second type, which is more common, critical parts of the macula are weakened, allowing abnormal new blood vessels to break through and bleed. This second type of macular degeneration leads to scarring of the macula and severe loss of the central area of vision. People may initially notice distortion of straight lines and then a dark or greyish patch develops in the centre of vision, completely obscuring what they are looking at.
Smoking may cause both types of macular degeneration and the resulting blindness is irreversible. The process can be stopped using laser treatment only if the condition is caught in its early stages.
Some interesting facts on smoking and macular degeneration:
- Macular degeneration is the leading cause of blindness in Australia and smoking is the major preventable cause of this condition.
- The chemicals in cigarette smoke (around 4000 of them) get into the bloodstream of smokers and may induce the damage to the macula, at the back of the eye. This damage results in macular degeneration and blindness over time.
- The damage from macular degeneration limits the ability of a person to see what they are looking directly at (such as the face of someone they are talking to).
- Macular degeneration also limits colour vision.
- Laser surgery cannot reverse the damage resulting from macular degeneration (except in a minority of cases detected in the very early stages). However, laser surgery may retard and or prevent the progression of the disease and reduce the visual loss. Recurrence of the condition occurs in about half of those who have initial successful laser treatment. For people who continue to smoke, almost all develop a recurrence.
- An estimated 20,000 Australians have macular degeneration that can be attributed to their smoking and around 8,000 of these people develop legal blindness in both eyes that is likely to have been caused by their smoking.
- In Australia you are legally blind if you cannot read the top letters on an eye chart with either eye from six metres.
- Many people with macular degeneration do not realise that they have the condition until their second eye starts to deteriorate, as one eye can compensate for the other.
- Up to two thirds of people with macular degeneration in one eye will ultimately lose sight in both eyes from this condition.
- When a smoker quits, the recovery process in some other parts of the body can begin almost immediately. Although it is not known whether stopping smoking reduces the risk to the second eye, it seems likely given evidence that links current smoking to development of macular condition.
- Providing they live long enough, one in four people will lose vision because of macular degeneration. Smoking increases this risk dramatically and may cause the loss of vision at an earlier age than it might otherwise occur. Top of page
Smoking and eye damage - Questions and answers
How does smoking damage my eyes?When you inhale cigarette smoke thousands of chemicals get into your bloodstream and can travel throughout your body. These chemicals cause damage to the macula (the most sensitive part of the retina, at the back of your eye). Tiny blood vessels can burst through the macula, leading to irreversible damage, or alternatively, the cells of the macula slowly die. Both ultimately lead to loss of vision.
Can this damage be reversed?No. Laser treatment can sometimes kill the new blood vessels before they hit the macula. However, most people are not able to be helped this way because the blood vessel has already involved the very centre of the macula, and even after treatment, the condition recurs in half the cases and in almost all those who continue to smoke. A new treatment, photodynamic therapy (PDT) may be able to help some to reduce the severity of vision loss, but the majority of people with macular degeneration will still not be able to be treated.
How long does it take for my eyes to become damaged?At this stage, there is no research to confirm at what point the damage occurs, however it is known that the process of macular degeneration is the result of progressive damage over many years. The condition is not usually detected until people are in their fifties or are older.
If I quit smoking will my eyes recover?Your risk of macular degeneration will be reduced if you quit smoking, however existing damage to the eyes cannot be repaired, particularly once vision is affected.
Is there a test to tell if my eyes are damaged?Your general practitioner or optometrist may be able to perform a simple test to indicate if your eyes are damaged. An ophthalmologist (eye specialist) will be able to determine the extent of the damage. You need to be seen urgently by an ophthalmologist if you suddenly become aware of distorted vision in one eye or if you notice a dark or greyish patch near the centre of your vision in one eye.
Chemicals in cigarette smoke get into the bloodstream and cause damage to the macula (part of the retina in the eye).
There is no cure for macular degeneration and not smoking or stopping smoking is one way to decrease the chances of developing this eye disease.
Eye expert statementAge-related macular degeneration (AMD), also termed age-related maculopathy (ARM), is the leading cause of blindness in Australia1-3. Its prevalence rises from less than 0.5% of people in their forties or fifties to around one in three of those aged in their nineties. People with AMD generally retain some mobility if their peripheral vision is maintained, but they are unable to read, drive or recognise people’s faces. Unfortunately, conventional laser treatment benefits only a small minority of people with AMD. The newer photodynamic therapy is likely to be helpful for well under half of the cases presenting, cannot reverse visual loss in most cases, is very costly and its long-term efficacy is not yet known. Until safe and effective treatments for AMD can be developed, primary prevention measures must be considered.
Based on data from two large population-based Australian studies4,5, there are currently around 34,500 people aged over 50 with legal blindness in Australia. Of these, around 80% are due to AMD4. Two late stage AMD lesions causing visual loss have been defined; a neovascular lesion (neovascular AMD) characterised by macular bleeding and scarring, responsible for two thirds of cases and an atrophic macular lesion (geographic atrophy), which accounts for the remaining third2.
Recent population-based cross-sectional data from four countries6-9 including Australia10 together with data from two large cohort studies11,12, have consistently identified smoking as the strongest environmental risk factor for AMD. All of these studies have shown that current smoking confers a greater risk than past smoking with the risk increased by between 2 and 5-fold. Several studies have demonstrated a dose response with pack years of smoking9,11,12 and a decreased risk with longer duration since cessation7. Evidence of a gradient between amount smoked and ARM severity has also been shown7,10. Although the Macular Photocoagulation Study report13 did not find an association between a history of current smoking at baseline and new cases of AMD, recurrences of the AMD lesions after laser were almost inevitable in persons who continued to smoke (85%), compared with non-smokers (50%). In longitudinal data reported from the Beaver Dam Eye Study14, smoking was related to the incidence of large drusen, the principal precursor lesion for late stage AMD lesions15 in both men and women. Data from the Australian Blue Mountains Eye Study presented at the 2000 Association for Vision & Ophthalmology meeting indicated that smoking was significantly associated with the incidence of atrophic AMD and precursor early age-related maculopathy lesions, particularly macular pigmentary changes16. Mechanisms for the smoking-AMD link are not known, but smoking may have a direct toxic effect on retinal cells and may cause vasoconstriction in the retina. Smoking is also known to reduce the absorption of protective antioxidants from the diet as well as reducing the density of protective macular pigments.
Although only a small proportion of older Australians are still smoking, smokers are disproportionally represented among cases of AMD. Researchers from the Blue Mountains Eye Study in New South Wales estimate that around 20% of AMD can be attributed to smoking17. This includes more than 20,000 of the estimated 100,000 current AMD cases in Australia and more than 8,000 Australians whose blindness from AMD can be attributed to their smoking. Unpublished data from the Visual Impairment Project in Victoria suggest that 14% of AMD is due to smoking.
The public should be educated about the risk of AMD and vision impairment due to cigarette smoking. A new cigarette pack warning about this link has been proposed17. Research from the Visual Impairment Project identified the fear that people have of losing their eyesight18. When asked to identify which of five disabilities that they would first provide treatment and support, 58% of Melbourne participants aged 40 years and older nominated "total blindness", the next most common being paralysis on one side due to a stroke (21%). This fear of blindness may be able to be used to successfully encourage people to quit smoking and discourage people from beginning to smoke. At present, this is the primary prevention strategy for AMD with greatest potential.
This paper has been written with the assistance of:
Associate Prof Paul Mitchell, Save Sight Institute, University of Sydney, Australia
Prof Hugh Taylor, Managing Director, Centre for Eye Research Australia
Associate Prof Cathy McCarty, Centre for Eye Research Australia,
Dr Wayne Smith, The National Centre for Epidemiology and Population Health, Australian National University
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