Inflammation and keratoconus.

Keratoconus (KC) has been traditionally classified as a noninflammatory disease. Barring loss of function, the other classic signs of inflammation (heat, redness, swelling, pain) are not usually obvious or even apparent in KC. This clinical perspective examines the evidence and implications of numerous inflammatory processes that have been recognized in the tears of KC patients as well as some inflammation relevant differences found in the KC cornea. The roles of inflammation in corneal trauma attributed to eye rubbing and/or contact lens wear are examined as is the significance of atopy, allergic disease, dry eye disease, degradative enzyme activity, wound healing, reduced anti-inflammatory capacity, and ultraviolet irradiation. It is possible that any comorbidity that is inflammatory in nature may add synergistically to other forms of KC-related inflammation and exacerbate its pathogenetic processes. For example, some features of inflammation in ocular rosacea and associated corneal thinning and distortion could have some possible relevance to KC. An analogy is drawn with osteoarthritis, which also involves significant inflammatory processes but, like KC, does not meet all the classic criteria for an inflammatory disease. Classifying KC as quasi-inflammatory (inflammatory-related) rather than a noninflammatory disease appears to be more appropriate and may help focus attention on the possibility of developing effective anti-inflammatory therapies for its management.