SNP Shot: Genomic Insights

Microphthalmia is a birth defect where one or both eyes are abnormally small. While sometimes the eye may appear absent, some eye tissue is usually present. This severe form of microphthalmia is different from anophthalmia, where the eye completely fails to develop. However, these terms are often used interchangeably. The impact on vision due to microphthalmia varies.

Individuals with microphthalmia may also experience coloboma. Colobomas involve missing tissue in eye structures, appearing as notches or gaps in the iris (colored part of the eye), the retina (light-sensitive tissue at the back of the eye), the choroid (blood vessel layer beneath the retina), or the optic nerves (transmitting visual information to the brain). Colobomas can occur in one or both eyes and affect vision depending on their size and location.

Other eye abnormalities can also be present with microphthalmia, such as cataracts (clouding of the lens) and a narrowed palpebral fissure (narrowed eye opening). Some individuals may also have microcornea, where the cornea (the clear front part of the eye) is small and abnormally curved.

In approximately one-third to one-half of cases, microphthalmia is part of a larger syndrome affecting other body parts. These are called syndromic cases. When microphthalmia occurs on its own, it's classified as nonsyndromic or isolated.

Inheritance:

Isolated microphthalmia can be inherited in an autosomal recessive manner, meaning both parents carry a mutated gene copy but usually don't show symptoms. In some instances, parents may have milder eye abnormalities. When microphthalmia is part of a genetic syndrome or chromosomal issue, it can run in families following the inheritance pattern of that specific condition (which might be autosomal recessive or another pattern). Often, microphthalmia is not inherited, and only one person in the family is affected.