Epidemiology

The annual incidence of infectious keratitis in the developed world has been increasing due to higher rates of contact lens use, and is now 2 to 11 per 100,000 per year.[3][4][5] A study from Hong Kong found an annual incidence of 0.63 per 10,000 in non-contact lens wearers and 3.4 per 10,000 in contact lens wearers.[4]Acanthamoeba keratitis, unknown prior to 1973, now accounts for approximately 1% of all cases, with contact lens use acting as a major risk factor.[6][7] Among contact lens wearers, most patients present between 20 to 29 years of age, reflecting the age distribution of contact lens users,[4][6] although contact lens-related infections are also encountered in younger and older patients. No clear sex differences are borne out in epidemiological studies.[3][4][6] The incidence of infectious keratitis in the developing world is considerably higher. In Nepal, for example, the rate is estimated to be 799 per 100,000 per year.[8] Fungi cause keratitis in about 6% of patients in temperate climates, but figure more prominently in tropical regions.[7] In South India, 35% of corneal ulcers were due to bacteria and 32% were due to fungi.[9] Another study in eastern India found that 62% of the corneal ulcers were due to fungi.[5]

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