F Rezvan - Noor Ophthalmology Research center, Noor eye hospital, Tehran. Iran
M Khabazkhoob - Noor Ophthalmology Research center, Noor eye hospital, Tehran. Iran
E Hooshmand - Noor Ophthalmology Research center, Noor eye hospital, Tehran. Iran
A Yekta - Noor Ophthalmology Research center, Noor eye hospital, Tehran. Iran

Purpose: The present study was conducted to determine the global prevalence and risk factors for pterygium. Methods: 3255 articles were identified, of which 68 articles with a total of 415,911 participants in 24 countries were included in the final analysis. Results: The prevalence of pterygium in the total population was 12% (95% CI 11% - 14%). The lowest and highest prevalence rates were respectively 3% (95% CI 0.0% - 9%) in the 10 to 20 year age group and 19.5% (95% CI 14.3% - 24.8%) in those over 80. The prevalence was 13% (95% CI 11% - 15%) in men and 12% (95% CI 9% - 13%) in women. The odds ratio for men was 1.30 (95% CI 1.14 - 1.45). The lowest prevalence of pterygium was reported in a clinic-based study in Saudi Arabia (0.07%) and the highest prevalence was in China (53%). The odds were 1.24 (95% CI 1.11 - 1.36) for sunlight exposure over 5 hours, 0.84 (95% CI 0.74 - 0.94) for smoking, 1.45 (95% CI 1.33 - 1.57) for living in rural areas, 1.17 (95% CI 1.03 - 1.32) for alcohol consumption, 1.46 (95% CI 1.36 - 1.55) for outdoor occupations, and 0.47 (95% CI 0.19 - 0.57) for use of sunglasses. Conclusion: According to our results, pterygium risk factors fall in three categories: demographic, environmental, and lifestyle factors. Older age, male gender, outdoors occupation, and living in rural environments are the leading demographic risk factors for the development of pterygium. Exposure to sunlight is the most common environmental risk factor, and the results of this study provide a more exact and reliable value of the effect of sunlight exposure. The use of sunglasses and cigarette smoking as protective factors, and the significant effect of alcohol consumption are factors related to lifestyle.