GDF6 and microphthalmia: Mutations in numerous genes including RAX, PAX6, SOX2, OTX2, VSX2, RARB, BMP7, BCOR, BMP4, FOXE3, STRA6, SMOC1, SHH, SNX3, MFRP, PRSS56, GDF3, GDF6, TENM3, C12orf57, YAP1, ABCB6, ATOH7, VAX1, NDP, ALDH1A3 and SMARCA4 have all been described in association with microphthalmia, and some, including RAX, PAX6, SOX2, OTX2, RARB, BMP7, BCOR, BMP4, FOXE3, STRA6, SMOC1, GDF6 and ALDH1A3 have also been described in association with anophthalmia [3–5].