Wu et al. (2017) found that long-term exposure to ultraviolet radiation caused the upregulation of these factors, which may result in pterygium. VEGF was demonstrated to be the most potent factor (Detorakis and Spandidos, 2009). Fukuhara et al. (2013) showed that VEGF expression was increased in the vascular endothelial component of pterygium compared with the normal conjunction. Here, VEGFA is linked to pterygium.