Many gene mutations impact the normal formation of the eye. Colobomas reflect incomplete closure of the primitive eye cup during development and they can appear in various ocular structures. In the condition described here, the optic nerve that carries visual impulses from the eye to the brain is incompletely formed. Its function is impaired to a variable degree which causes decreased vision.
The malformation in the optic nerve is sometimes but not always associated with a small eye and/or a small cornea (windshield of the eye). It is a congenital, nonprogressive condition and usually is found in both eyes. Visual acuity varies widely depending upon the structures that are involved. Since the disorganized tissue is inside the eye, simple inspection usually does not reveal any abnormality which may lead to a delayed diagnosis in children.
Optic nerve colobomas are often the result of a gene mutation. They occur in an autosomal dominant pattern as the malformation is passed directly from parent to child. An affected parent transmits the mutation with a 50% probability to each child.
The diagnosis is usually made by an ophthalmologist by a detailed examination of the eye. It is a stable condition but there is no treatment for a malformed optic nerve. Low vision devices can be helpful for patients who have some vision.