An allelic test with Gja8 knockout (−/−) mice revealed that, in contrast to normal eye size of Nm2249/+ heterozygous mutant mice (Figure 1A), mutant mice (Nm2249/−) with one Nm2249 allele and one Gja8 knockout allele had phenotypes similar to Nm2249/Nm2249 homozygous mutant mice (Figure 1E), including microphthalmia and small lenses with dense nuclear cataracts. This evidence concerns the gene GJA8 and microphthalmia.