Contributor: Gordon K Klintworth
Keratitis has many causes including bacteria [keratitis - bacterial], viruses [keratitis - viral], chlamydia [keratitis - chlamydial],  fungi [keratitis - fungal], protozoa [keratitis - protozoal], nematodes [keratitis - nematodal], ultraviolet light [actinic keratitis], rosacea [keratitis - rosacea],  aerosols [keratitis - aerosol], vapors [keratitis - vapor spray], dry eyes [keratitis sicca], facial nerve palsy  [keratitis - neuroparalytic], corneal anesthesia [keratitis - neurotrophic], excessive exposure of the eyes to air [keratitis - exposure], wounding of the cornea by some grains [keratitis - reapers], and artificial silk [keratitis - artificial silk]. Contact lens wear is associated with an increased risk of infectious keratitis [keratitis - infectious]. Based on the clinical appearance of the cornea or the location of the abnormalities keratitis is divided into several types: dendritic keratitis [keratitis - dendritic], keratitis petrificans, band keratitis [keratitis - band], deep keratitis [keratitis - deep], hypopyon keratitis [keratitis - hypopyon], keratitis filamentosa, purulent keratitis [keratitis - purulent], keratitis punctata subepithelialis, phlyctenular keratitis, vascular keratitis [keratitis - vascular], sclerosing keratitis [keratitis - sclerosing], striate keratitis [keratitis - striate], marginal keratitis [keratitis - marginal], keratitis bullosa, catarrhal ulcerative keratitis [keratitis - catarrhal ulcerative], chronic superficial keratitis [keratitis - chronic superficial], deep pustular keratitis [keratitis - deep pustular], disciform keratitis [keratitis - disciform], epithelial diffuse keratitis [keratitis - epithelial diffuse], superficial punctate keratitis [keratitis - superficial punctate]), exfoliative keratitis [keratitis - exfoliative], fascicular keratitis [keratitis - fascicular],  lattice keratitis [keratitis - lattice], peripheral ulcerative keratitis [keratitis - peripheral ulcerative],  deep punctate keratitis [keratitis - deep punctate],  superficial punctate keratitis [keratitis - superficial punctate], deep pustular keratitis [keratitis - deep pustular], secondary keratitis [keratitis - secondary], ulcerative keratitis [keratitis - ulcerative], vesicular keratitis [keratitis - vescicular], zerotic keratitis [keratitis - zerotic]. Bacterial endophthalmitis [endophthalmitis - bacterial] may follow bacterial keratitis. The use of topical corticosteroids on the eye dramatically dampens the effects of neutrophil-mediated inflammation. The lack of inflammatory response to invading bacteria in pseudocrystalline keratopathy is the result of topical corticosteroids. Bacteria proliferate relatively unimpeded between collagen lamellae in the virtual absence of inflammation. Infectious pseudocrystalline keratopathy is frequently caused by the growth of minimally virulent bacteria, such as S. viridans, and usually occurs in eyes having had previous accidental or surgical trauma. Keratitis is a manifestation of several inherited diseases (autosomal dominant keratitis [keratitis - autosomal dominant], EEC syndrome, KID syndrome, keratoendothelitis fugax hereditaria, and epidermolysis bullosa simplex).