Microphthalmia (MAC) is a genetic disease that results in abnormally small eyes at birth due to a vitamin A deficiency during gestation. Malformations of different parts of the eye can eventually lead to vision loss. These eye abnormalities are evident soon after birth and can be observed by a veterinarian during an eye exam which can determine the level of vision impairment. This disease is inherited in a recessive manner with what is known as maternal effect. This means that a dog must have two copies of the mutation and be born to a mother that also has two copies of the mutation to suffer symptoms of the disease. This is due to the fact that the vitamin A supply to the fetus is impaired by the affected mother. Dogs with two copies of the mutation born to a mother that carries one copy of the mutation will likely not develop symptoms of this disease.
- Soft-Coated Wheaten Terrier
A (CLEAR/NORMAL): These dogs have two copies of the normal gene and will neither develop microphthalmia nor pass this mutation to their offspring.
B (CARRIER/NOT AFFECTED): These dogs have one copy of the normal gene and one copy of the mutation associated with this disease. They will not develop microphthalmia but will, if bred, pass the mutation to 50% of its offspring, on average.
C (AT RISK/AFFECTED): These dogs have two copies of the mutation associated with this disease and are susceptible to developing microphthalmia if they are born to a mother that carries two copies of the mutation.