Methodological quality of the review: Low confidence

Author: Health Quality Ontario

Geographical coverage: United States of America (USA), India, Australia

Sector: Glaucoma

Sub-sector: Risk factors for glaucoma

Equity focus: Age group 20-64 years old

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background: Identifying risk factors via routine eye examination for developing glaucoma is very important for early diagnosis. Treatment may consequently prevent or delay disease progression.

Objectives: To estimate the strength of association between age, gender, ethnicity, family history of disease and refractive error and the risk of developing glaucoma or age-related maculopathy (ARM).

Main findings: A total of 498 citations for the period January 2000 to February 2006 were retrieved and an additional 313 were identified when the search was expanded to include articles published between 1990 and 1999. An additional six articles were obtained from bibliographies of relevant articles. Of these, 36 articles were retrieved for further evaluation. Upon review, one meta-analysis and 15 population-based epidemiological studies were accepted for this review.

Six cross-sectional studies and one prospective cohort study contributed data on the association between age and primary open angle glaucoma (POAG). From the data, it can be concluded that the prevalence and four-year incidence of POAG increases with increasing age. The odds of having POAG are statistically significantly greater for people 50 years of age and older relative to those 40 to 49 years of age. There is an estimated 7% per year incremental odds of having POAG in persons 40 years of age and older, and 10% per year in persons 49 years of age and older. POAG is undiagnosed in up to 50% of the population. The quality of the evidence was moderate.

Five cross-sectional studies evaluated the association between gender and POAG. Consistency in estimates is lacking among studies and, because of this, the association between gender and prevalent POAG is inconclusive. The quality of the evidence is very low.

Only one cross-sectional study compared the prevalence rates of POAG between black and white participants, and suggests that prevalent glaucoma is statistically significantly greater in a black population aged 50 years and older compared with a white population of similar age. There is an overall four-fold increase in prevalent POAG in a black population compared with a white population. This increase may be due to a confounding variable not accounted for in the analysis. The quality of the evidence was low.

Methodology: The following databases were searched: Ovid MEDLINE, MEDLINE, In-Process and Other Non-Indexed Citations, EMBASE, INAHTA and the Cochrane Library for Relevant Studies. References of relevant papers were searched for additional papers. The search was limited to English-language articles published from January 2000 to March 2006.

The following inclusion criteria were applied:

• Studies including participants aged 20 years and older
• Population-based prospective cohort studies
• Population-based cross-sectional studies when prospective cohort studies were unavailable or insufficient
• Studies determining and reporting the strength of association or risk-specific prevalence or incidence rates of either age, gender, ethnicity, refractive error or family history of disease and the risk of developing glaucoma or AMD.

One reviewer evaluated the eligibility of the citations retrieved, extracted data from the included studies, and evaluated the internal validity of the primary studies. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) system was used to summarise the overall quality of the body of evidence.

Applicability/external validity: Authors did not discuss the applicability/external validity of findings.

Geographic focus: The review did not focus specifically on low/middle-income countries, though results from low/middle-income settings such as India were included.

Summary of quality assessment: Authors conducted a narrative synthesis of the findings, which seemed appropriate due to the differences of included studies such as the difference in study population. Authors appropriately reported inclusion/exclusion criteria used for study selection. However, this review had some important limitations. The authors did not avoid language bias, as only articles written in English were included in the review. Only one reviewer has identified, selected and quality-appraised relevant articles. Therefore, there is low confidence in the conclusions about the effects of this study.