Conjunctivochalasis is the precursor to pterygium

摘要

Pterygium is a fibrovascular proliferative condition of the ocular surface with no known pathological mechanism. This condition affects vision due to dry eyes, astigmatism or physical occlusion of the visual axis for severe cases. The only definitive treatment for this condition is surgical excision. Interestingly, it is a lesion that may be related to UV radiation and elaboration of proteases. Conjunctivochalasis is a dry eye related condition that is exemplified by excessive conjunctiva or the mucous membrane of the front of the eye around the cornea. Both pterygium and conjunctivochalasis are associated with elaboration of matrix metalloproteinases as well as inflammatory cytokines. We propose that under specific conditions, conjunctivochalasis in the nasal part of the conjunctiva can progress to pterygium. The progression of conjunctivochalasis to pterygium may be related to special kinds of oxidative or inflammatory damage that affects only the part of the loose conjunctival tissue adjacent to the cornea. Protease expressed may then breakdown the conjunctival and corneal epithelium causing the head of pterygium to be very adherent to the cornea. This explains the fact that surgically excised pterygium tissue has stromal tissue enclosed by epithelia on both surfaces. In addition, it explains the existence of a surgical plane when an instrument is passed under the neck of the pterygium tissue but not at the apex. The implications of this hypothesis are first, treatment should be directed to the protection of conjunctivochalasis before it transforms to pterygium. This may be achieved by anti-inflammatory measures, anti-protease treatment, or preventing the triggering of the changes at the head of pterygium, such as avoidance of sunlight. Second, during resection of pterygium, it may not be necessary to resect the pterygium too extensively away from the cornea, since this effectively removes relatively normal conjunctiva.