Topological-histological investigation of the pterygium

Abstract

Background: It is a wide-spread assumption, never proven scientifically, that the pterygium is a duplication of the conjunctiva, with an intervening gap at the limbus. We therefore conducted a histological reinvestigation, primarily to clarify the topological relation between normal bulbar tissue and lesion.

Methods: Excised pterygia were prepared for light microscopy and embedding in paraffin. Two pterygia were serially sectioned, and samples of 49 others were removed, sectioned and stained (stains: H&E, alcian blue, toluidine blue, PAS; antibody: cytokeratin 18).

Results: The pterygium is an epithelium-covered protuberance of connective tissue, projecting over the normal surface of the eyeball; it consists of a base, which extends in the direction of growth, and lateral lobes. It is therefore impossible to insert a probe all the way under a pterygium. The bulbar tissue adjacent to the pterygial protuberance can likewise be histologically altered. That is, a narrow layer of connective tissue, well supplied with capillaries, may be present in the corneal section of the pterygium between Bowman's layer and the epithelium.

Conclusion: Histological alterations of the stroma predominate quantitatively over those of the epithelium. The topographical anatomy of the lesion and the fact that bulbar tissue is modified along with the pterygium 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 reduced.