The microphthalmia in Soft-Coated Wheaten Terriers is a congenital ocular malformation associated with a mutation (K12del) in the RBP4 gene, which disrupts the transport of vitamin A essential for eye development. The disease follows a particular inheritance pattern dependent on a maternal effect, where the genotype of the mother directly influences embryonic development. It results in an abnormally reduced development of one or both eyes in the puppy.
This test is also mandatory for the Jack Russell Terrier as part of the Flemish government's official breeding program (see official program).
