Methodological quality of the review: Low confidence
Author: Lois N, Abdelkader E, Reglitz K, Garden C, Ayres JG.
Region: Details not provided
Sector: Eye disease
Sub-sector: Tobacco smoke exposure
Type of cataract: Age-related cataract
Equity focus: None specified
Review type: Effectiveness review
Quantitative synthesis method: Narrative synthesis
Qualitative synthesis methods: Not applicable
Environmental tobacco smoke (ETS) exposure is known to either exacerbate or initiate a range of diseases including lung cancer, asthma in children and cardiovascular disease. Although ETS is an accepted risk factor for several eye disorders, its potential to initiate or exacerbate conditions of the eye is not well established.
To undertake a systematic review of the literature on the effect of environmental tobacco smoke (ETS) and eye disease.
In total, authors included seven studies in the systematic review, consisting of cross-sectional and case control studies evaluating the possible relationship between ETS and an eye disease.
Included studies evaluated the relationship between ETS and refractive error in children, cataract, age-related macular degeneration (AMD) and Graves ophthalmology. The data available in the review were insufficient to establish conclusive relationships between ETS and these eye diseases. There is only circumstantial evidence that ETS is linked with Graves ophthalmology. Scarce data exists on the association between ETS and AMD, cataract and refractive error. It was noted from one large cross sectional study that passive smoking was not statistically significantly associated with the development of cataract, but pipe smoking was strongly associated with nuclear cataract.
As such, due to the scarcity of data, authors recommended further research on the association between ETS and eye diseases.
The authors conducted literature searches on MEDLINE (1950-2007), EMBASE (1980–2007), SCOPUS and Science direct on ETS exposure generally and also eye diseases where smoking was proposed as a risk factor including AMD, Graves ophthalmology, glaucoma and refractive errors. Additionally, the Association for Research in Vision and Ophthalmology Annual Meeting abstracts were searched (1995–2006), and also a search of the grey literature for PhD and MSc theses/dissertations was undertaken. Geographical location of the studies was not addressed in the review, and also it is not clear whether language restrictions were applied to searches. It was noted that all studies found, independently of their quality, were included in the review as very few studies were conducted to date. The review cites animal studies to support included study findings.
The authors did not address the applicability/external validity of the results.
The review did not specifically focus on low- and middle-income countries, and geographical location was not specifically addressed in the review.
This review was attributed low confidence in the conclusions about the effects of this study as major limitations were identified. The systematic review was based on searches of major databases including MEDLINE and Scopus and other grey literature and authors reported date and search terms. However, it was not clear if the authors avoided language bias in the search, if they searched the reference lists of included studies or contacted authors of included studies for additional information. It was also not clear if study selection and data extraction were independently conducted by two authors.
The review identified studies that reported a range of outcomes with different study designs and as such, a narrative analysis was appropriate. Authors recognized that studies evaluating the association between ETS and eye disease are scarce and acknowledged that all studies found were included in the review, regardless of quality. Nevertheless, review authors listed study limitations for each included study in terms of study design and/or outcomes. Furthermore, no strong policy conclusions were drawn from this study.