Microphthalmia in the Irish Soft Coated Wheaten Terrier is a congenital eye disorder caused by a K12del mutation in the RBP4 gene, which disrupts the transport of vitamin A essential for eye development. The condition only manifests when both the dam and the offspring are homozygous for this mutation. Affected dogs show significantly underdeveloped eyes (one or both), sometimes accompanied by hematological abnormalities. This test is also mandatory for the Jack Russell Terrier as part of the Flemish government's official breeding program (see official program).
