Corneal Degenerations

Degenerations are defi ned as the gradual deterioration of a tissue or an organ that was previously normal with frequent loss of functional activity. Corneal degenerations are characterized by the deposition of material, thinning of tissue, and vascularization. Contrary to corneal dystrophies, they are not hereditary and could be unilateral. Moreover, because of the continuous exposure to environmental conditions, the cornea might undergo changes related to UV stimulation, and in some cases, oxidative stress might be responsible for the onset of degenerative processes [ 1 , 2 ]. Corneal degenerations are characterized by a late onset; they can occur in several local diseases with mainly unilateral involvement or result from underlying systemic disorders or age-related processes. In the latter cases, they are bilateral even if asymmetric. Corneal degenerations can be classifi ed with relation to corneal changes. Generally, forms with abnormal peripheral corneal thinning and those with material deposition are recognized. The thinning processes are mainly of unknown etiology even if some general coexisting disorders were reported. In degenerations characterized by material deposition, the local and systemic causes underlying the corneal involvement could usually be identifi ed [ 1 ].