RESUMO
PURPOSE: Ultraviolet rays, dust, and the human papilloma virus are well known as extrinsic risk factors in pterygium pathogenesis, but the intrinsic factors and nasal predominance related to the development of pterygium have not been fully ulucidated. Herein, we sought to determine whether the relative ischemic state of nasal bulbar conjunctiva affects the development of nasal predominance in pterygium pathogenesis. METHODS: Anterior segment fluorescein angiography was performed and the anterior bulbar conjunctival temperature was obtained to identify the presence of nasal ischemia. Tear samples were collected from both a normal and a patient group. The difference in SDF-1 (stromal cell-derived factor-1) was determined through ELISA and Western blot anyalyses. The excised pterygium tissues were immunohistochemically stained by antibodies for HIF-1 (hypoxia-inducible factor-1), SDF-1, and CXCR4. RESULTS: Results of the anterior segment fluorescein angiography showed that, the vascularity of the nasal limbus was lowest among each groups and the nasal filling time was significantly delayed in the patient group. The temperature of the nasal bulbar conjunctiva was lower than that of the temporal bulbar conjunctiva. The concentration of SDF-1 in tears was significantly higher in the patient group. In the immunohistochemical stain, HIF-1, SDF-1, and CXCR4 were revealed at epithelial basal cells or vascular endothelia in the stroma and the stained areas corresponded to each other. CONCLUSIONS: From the above results, we assumed that low nasal vascularity and temperature resulted in relative ischemic state and this hypoxic injury may be a major risk factor in pterygium development through the mobilization of endothelial progenitor cells by HIF-1 induced SDF-1 overexpression.