PDGFRA and Corneal astigmatism: We genotyped 13 SNPs in the PDGFRA gene region: nine tagging SNPs (rs11133315, rs6554162, rs2303429, rs7656613, rs1547905, rs3816888, rs17739921, rs1826426, and rs6554170) and four SNPs reportedly associated with corneal astigmatism in previous studies (rs7673984, rs4864857, rs6554163 and rs7677751)9–12.