Topological-histological investigation of the pterygium

Background: It is a widespread assumption, never proven scientifically, tha t the pterygium is a duplication of the conjunctiva, with an intervening ga p at the limbus. We therefore conducted a histological reinvestigation, pri marily to clarify the topological relation between normal bulbar tissue and lesion. Methods: Excised pterygia were prepared for light microscopy and e mbedding in paraffin. Two pterygia were serially sectioned, and samples of 49 others were removed, sectioned and stained (stains: H&E, alcian blue, to luidine blue, PAS; antibody: cytokeratin 18). Results: The pterygium is an epithelium-covered protuberance of connective tissue, projecting over the n ormal surface of the eyeball; it consists of a base, which extends in the d irection of growth, and lateral lobes. It is: therefore impossible to inser t a probe all the way under a pterygium. The bulbar tissue adjacent to the pterygial protuberance can likewise be histologically altered. That is, a n arrow layer of connective tissue, well supplied with capillaries, may be pr esent in the corneal section of the pterygium between Bowman's layer and th e epithelium. Conclusion: Histological alterations of the stroma predominat e quantitatively over those of the epithelium. The topographical anatomy of the lesion and the fact that bulbar tissue is modified along with the pter ygium should be taken into account when excision is undertaken. We predict that if all the altered tissue is removed, the rate of recurrence will be r educed.