1. Introduction
Astigmatism is a common optical disorder and exists in most
human eyes in subtle amounts. Numerous studies have reported
the prevalence of astigmatism in different ages [1–7], rural and
urban populations [8–10] and ethnic groups [1–10]. Previous
studies have reported the prevalence of astigmatism from 11.3% up
to 70% in related studies [5,7,8]. Different factors have been