Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to microphthalmia ?
    ### Response:
    Microphthalmia may be caused by changes in many genes involved in the early development of the eye, most of which have not been identified. The condition may also result from a chromosomal abnormality affecting one or more genes. Most genetic changes associated with isolated microphthalmia have been identified only in very small numbers of affected individuals.
    