**3. Epidemiology**

The most common causative factor of IK in most regions is bacteria. BK represents the following percentage of IK, including the UK (91–93%) [17, 18], Middle East (91.8%) [19], North America (86–92%) [20], South America (79–88%) [21], and Australasia (93–100%) [22]. In the USA, the incidence of MK is 71tousends cases per year USA [23]. There is a huge disproportion in the incidence of BK between developing and developed countries. This disparity of prevalence and incidence of BK is because of differences in geographical location and environmental and climate risk factors. The contact lens' users are also significant. The pathogenesis of CL-related corneal inflammation is complex and multifactorial. CL-related IK occurs particularly in the developed and industrialized countries have been a higher frequency of contact lens' users, and as a result, there is a higher rate of contact lens-related bacterial keratitis [24, 25]. It is commonly believed that CL-related IK is caused by superficial injury secondary to CL wear. However, there are several studies in which have been shown that the presence or absence of epithelial injury did not influence the risk or severity of IK [26]. As we mentioned before, *Pseudomonas keratitis* is one of the most common causes of BK, especially in the developed countries where there is increased prevalence of CL wear.
