Comparison of the Roles of Lymphatic Vessels and Blood Vessels in the Recurrence of Pterygia: A Retrospective Study

Purpose: Increased conjunctival arteries and lymphangions accelerate the cellular immune response in recurrent pterygium, however, which plays a more important role warrants further investigation. The aim of the study is to compare the roles of lymphatic and blood vessels in pterygium recurrence. Methods: Histological sections from 48 excised recurrent pterygia (including 14 Grade 1, 20 Grade 2, and 14 Grade 3 tissues) were examined. Histological sections from seven nasal epibulbar conjunctival segments served as normal controls. Blood and lymphatic vessels were evaluated and compared according to blood microvessel density (BMD), blood vascular area (BVA), lymphatic microvessel density (LMD), and lymph-vascular area (LVA). Furthermore, the following relationships were analyzed: LMD and pterygium recurrence time (RT), LVA and RT, BMD and RT, BVA and RT. Results: Compared to LVA, LMD, BVA, and BVD values in normal control tissues, these values were markedly enhanced in recurrent pterygia tissues. The LMD/BMD and LVA/BVA ratios were significant increased in Grade 2 and 3 recurrent pterygia, suggesting that development of conjunctival lymphangions was not proportional to blood vessel growth. LMD, LVA and BVA were significantly correlated with RT for all grades of pterygia, while BMD was the only factor correlated with RT in Grade 1 pterygia. Moreover, no significant correlation was found between BMD and RT in Grade 2 and 3 pterygia. Conclusion: Compared to blood vessels, lymphangions might have a greater impact on pterygium recurrence.