Flow cytometry measurements of DNA content in primary and recurrent pterygia

PURPOSE. To evaluate DNA content and cellular proliferation rates in primar y and recurrent pterygia. METHODS. Matched pterygium and superior conjunctiva tissue were obtained in 36 eyes of 36 patients undergoing pterygium excision with conjunctival aut ografting (24 primary pterygia, 12 recurrent pterygia). Epithelial and fibr ovascular layers were separated for analysis. Matched superior conjunctiva obtained at the time of surgery were used as controls. Samples were prepare d according to Thompson's method, and flow cytometry was performed with a B ecton-Dickinson FACScan. Analysis of histograms and calculations of cell pe rcentages in cell cycle phases were carried out using CellFit software (ver sion 2.0). Mean proliferation indices (MPIs) were compared using the Wilcox on matched-pair signed-rank test. RESULTS. The MPI of pterygium fibrovascular tissue (13.4) was significantly higher than the MPI of pterygium epithelium (3.1; P = 0.0001). The MPI of pterygium fibrovascular tissue was also significantly higher than that of s uperior conjunctival fibrovascular tissue (6.0; P = 0.0001). There was no d ifference in MPI values between pterygium epithelium anti superior conjunct ival epithelium (3.55; P = 0.12). The MPI of fibrovascular tissue from recu rrent pterygium (73.75) was significantly higher than the MPI of fibrovascu lar tissue from primary pterygium (7.3; P = 0.003). CONCLUSIONS. The finding of high levels of cellular, proliferation in the s ubepithelial fibrovascular layer of pterygium confirms that pterygium is a disorder of excessive cellular proliferation and that the fibrovascular lay er is the site of cellular proliferation. Markedly raised levels of cellula r proliferation in recurrent pterygium tissue suggest a clinical correlatio n between fibrovascular tissue upregulation and pterygium recurrence after surgery.