The phenotype of aniridia could be explained by the haploinsufficiency of the PAX6 protein, in which the mutated PAX6 protein does not have any transcriptional activity and the remaining single normal copy of PAX6 is not enough to produce a sufficient threshold level of biologically active PAX6 protein to initiate the transcription of its target genes [11,27,28]. This evidence concerns the gene PAX6 and isolated aniridia.