PURPOSE: A prospective interventional pilot study was performed to estimate the effect of ranibizumab injection on the clinical and histological picture of primary pterygium.METHODS: Five patients with primary pterygia received a single subconjunctival injection of ranibizumab (0.3 mg), whereas 5 nontreated pterygia served as controls. The treated pterygia were surgically removed 3 days, 1 week, 2 weeks, 1 month, and 2 months after the injection, respectively. Digital photographs of the pterygia were taken immediately before injection, 1 week after, and on the day of operation.RESULTS: Ranibizumab was well tolerated by all patients, and no side effects were reported. However, it had no effect on the extent of vascularization of pterygium, regardless of the interval between injection and operation. No regression of pterygium vessels was noted in any of the patients. Immunohistochemical analysis also showed no particular differences in the number of vessels stained positive for vascular endothelial growth factor A, in the intensity of vessel staining among the treated pterygia, and between the treated and the nontreated pterygia.CONCLUSIONS: Subconjunctival ranibizumab at a single dose of 0.3 mg was not associated with any side effects but had no effect on the extent of vascularization of primary pterygium in our study.