SOX2 and microphthalmia: Severe SOX2 mutations (whole gene deletion/nonsense) which most likely produce complete loss-of-function alleles almost uniformly result in anophthalmia/microphthalmia (47 out of 50 cases [11]), suggesting that these mutations result in a major disruption of eye development, while missense mutations are more likely to be associated with non-microphthalmia phenotypes (11 of 21 cases [11,12]).