Keratoconus: an inflammatory disorder?
Keratoconus has been classically defined as a progressive, non-inflammatory condition, which produces a thinning and steepening of the cornea. Its pathophysiological mechanisms have been investigated for a long time. Both genetic and environmental factors have been associated with the disease. Recent studies have shown a significant role of proteolytic enzymes, cytokines, and free radicals; therefore, although keratoconus does not meet all the classic criteria for an inflammatory disease, the lack of inflammation has been questioned. The majority of studies in the tears of patients with keratoconus have found increased levels of interleukin-6 (IL-6), tumor necrosis factor-α(TNF-α), and matrix metalloproteinase (MMP)-9. Eye rubbing, a proven risk factor for keratoconus, has been also shown recently to increase the tear levels of MMP-13, IL-6, and TNF-α. In the tear fluid of patients with ocular rosacea, IL-1α and MMP-9 have been reported to be significantly elevated, and cases of inferior corneal thinning, resembling keratoconus, have been reported. We performed a literature review of published biochemical changes in keratoconus that would support that this could be, at least in part, an inflammatory condition.
1] Centro Oftalmologico Virgilio Galvis, Floridablanca, Colombia [2] Faculty of Health Sciences, Universidad Autonoma de Bucaramanga, Floridablanca, Colombia.
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Galvis
Faculty of Medical and Health Sciences, Department of Ophthalmology, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand.
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Sherwin
1] Centro Oftalmologico Virgilio Galvis, Floridablanca, Colombia [2] Faculty of Health Sciences, Universidad Autonoma de Bucaramanga, Floridablanca, Colombia.
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0000000150810720
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Tello
Instituto Oftalmologico Fernandez-Vega, Oviedo, Spain.
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Merayo
Centro Oftalmologico Virgilio Galvis, Floridablanca, Colombia.
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Barrera
Bioftalmik Applied Research, Derio, Spain.
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Acera
D005136:Eye Proteins / Q000378:metabolism*; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D007634:Keratitis / Q000378:metabolism / Q000503:physiopathology*; D007640:Keratoconus / Q000378:metabolism / Q000503:physiopathology*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D013666:Tears / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D005136:Eye Proteins; C508600:IL6 protein, human; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; C042434:tear proteins; C579270:MMP9 protein, human; D020780:Matrix Metalloproteinase 9