The Relationship of Climate Factors and Pterygium Disease; Comparative Study of the Cities of Mashhad and Zahedan, Iran

Pterygium is a common disease of the eye affected by environmental factors, especially climatic parameters. The purpose of this study was to evaluate the influence of climatic factors on pterygium in the cities of Mashhad and Zahedan in Iran eastern half. The data of 130,464 patients referred to Zahedan Alzahra Ophthalmology Clinic (from them, 28,776 patients with pterygium) and 974,542 patients referred to Mashhad Khatam ol-Anbia Ophthalmology Clinic (from them, 20,222 patients with pterygium) during 2006-2011 were used. Climatic data elements including sunshine hours, dusty days, wind speed, ultraviolet and total sunshine index, maximum and minimum temperature, and humidity for two stations in Zahedan and Mashhad were obtained from the Iran Meteorological Organization. To study and compare the relationship of climatic factors and pterygium, correlation model, to analyze time delays, autocorrelation functions (ACF) and partial and autocorrelation functions (PACF), to assess seasonal differences in prevalence of pterygium model, ANOVA test, and to compare the prevalence of pterygium among patients in both two cities, independent sample t-test were used. In Zahedan, dusty days, sunshine hours, wind speed indicator, and ultraviolet and total sunshine indexes were the most effective factors on the prevalence of pterygium, respectively; while in Mashhad, wind speed, dusty days, and ultraviolet index were the most effective factors, respectively. ANOVA test showed no significant differences in terms of prevalence in different seasons. The t-test results showed that the prevalence of eye disease among patients in Zahedan was more than the city of Mashhad significantly. There was delay time in influencing the prevalence of pterygium by seasonal climate elements. In general, the incidence of pterygium was higher in Zahedan than Mashhad. It seems that the role of climatic factors in the incidence and severity of pterygium is more notable in Zahedan.