Dear Editor,

We welcome the publication of the case control study by Evans et al. [1] demonstrating the strong association between smoking and age-related macular degeneration (AMD). This important study adds evidence from the UK to a growing body of research linking smoking and AMD.

Readers may wonder why the estimated number of UK cases of AMD causing visual impairment attributable to smoking in the Evans et al. paper was approximately half the figure (28,000 vs. 54,000 cases) we published in 2004.[2] Numbers in both papers were calculated from population attributable risk calculations using estimates of AMD cases and smoking prevalence in the UK population. Similar methods were used in a paper which estimated that 20,000 AMD cases and over 8,000 people were blind in Australia from AMD attributable to smoking.[3]

As Evans and co-workers noted, the higher estimates in our BMJ paper reflected our use of a higher estimate or risk among current smokers (3.12 vs. 2.15); and also our inclusion of subjects aged 70 years and over, whilst Evans and colleagues included only subjects aged 75 years and over. An additional difference was that we (and the Australian paper) included risk of AMD among ex-smokers (RR = 1.36) as well as for smokers in our estimates. Evans et al did not estimate cases of AMD among ex-smokers because their study did not find a significantly raised risk in this group. The estimates may also have been affected by differences in the prevalence of smoking by age group used, though this was not clear, because these were not presented by Evans et al in their paper.

Our risk estimates were derived from a pooled analysis of three large (14,752 participants) population based cross-sectional studies [4] in the US, Australia and Netherlands. A subsequent pooled analysis based on 5 years of follow-up of a cohort of 9,430 participants in these three studies found a relative risk of 2.35 for current smokers, and a non- significantly raised risk of 1.29 in ex-smokers.[5] Using figures from this cohort study pooled analysis, revised estimates of number of UK cases of AMD causing visual impairment attributable to smoking are 41,350 when cases attributed to exposure among ex-smokers are included, and 21,800 if these are excluded.

Whilst the exact numbers vary, these estimates demonstrate that tens of thousands of people in the UK are affected by AMD attributable to smoking. This illustrates the public health importance of tobacco control and smoking cessation for the prevention of AMD. Evans et al’s study re- emphasises the importance of raising awareness of smoking as a cause of eye disease, and of eye health staff raising the issue of smoking with their patients. Drawing attention to the link between smoking and blindness is supported by the Royal College of Ophthalmologists and the Royal National Institute for the Blind, and may be a powerful message for health education campaigns, particularly as most eye and general out- patient clinic attenders remain unaware of the link.[6]

Yours truly,

Richard Edwards
Senior Lecturer in Public Health
Evidence for Population Health Unit
University of Manchester

Simon Kelly
Consultant Ophthalmic Surgeon
Bolton Hospitals NHS Trust

Georgios Lyratzopoulos
Consultant in Public Health
Norfolk Suffolk and Cambridgeshire Strategic Health Authority

Judith Thornton
Research Associate
Arthritis Research Campaign
Epidemiology Unit
University of Manchester

References

1. Evans JR, Fletcher AE, Wormwald 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;89:550-3.

2. Kelly SP, Thornton J, Lyratzopoulos G, Edwards R, Mitchell P. Smoking and blindness: strong evidence for the link, but public awareness lags. BMJ 2004;328(7439):537-8.

3. Mitchell P, Chapman S, Smith W. Smoking is a major cause of blindness. Medical Journal of Australia 1999;171:173-4.

4. Smith W, Assink J, Klein R, Mitchell P, Klaver CC, Klein BE et al. Risk factors for age-related macular degeneration: Pooled findings from three continents. Ophthalmology 2001;108(4):697-704.

5. Tomany SC, Wang JJ, Van Leeuwen R, Klein R, Mitchell P, Vingerling JR et al. Risk factors for incident age-related macular degeneration: pooled findings from 3 continents. Ophthalmology 2004;111(7):1280-7.

6. Bidwell G, Sahu A, Edwards R, Harrison R, Thornton J, Kelly SP. Perceptions of blindness related to smoking: a hospital based cross- sectional study. Eye (In press) 2005.

Dear Editor,

The growing research implicating smoking with age-related macular degeneration prompted us to write an editorial in 1999 [1] urging the Australian government to warn smokers of this little appreciated risk.

In 2000, the Australian National Quit campaign ran an advertisement as part of a series titled "Every cigarette is doing you damage" which explicitly addressed AMD. A website describes the campaign here http://www.quitnow.info.au/script/eye.html and the television ad may be downloaded here: http://www.quitnow.info.au/smokescreen/smokescreen.html.

In 2006 the Australian government will require new mandatory pictorial pack warnings, one of which will be about AMD. This warning was one of the strongest tested among smokers in the research conducted for the government prior to the announcement. The full report and other related information can be found at: http://tobacco.health.usyd.edu.au/site/supersite/resources/docs/gallery_ packwarnings.htm.

Reference

1. Mitchell P, Chapman S, Smith W. "Smoking is a major cause of blindness": a new cigarette pack warning? Med J Aust 1999;171:173-4.