Genetic counseling imparts knowledge of human disease, including a genetic diagnosis and its ocular and systemic implications. The genetic counseling process helps individuals, couples, and families understand the risk of occurrence or recurrence of the disorder within the family. It provides information about appropriate use and implications of available genetic testing, along with interpretation of results and reproductive options, as well as facts about therapies, research, and resources. Psychosocial issues are also an integral part of the discussion. Genetic counseling is nondirective and addresses ethical issues as well as ethnic and cultural diversity with sensitivity. All genetic counseling is predicated on the following essential requirements:
Issues in Genetic Counseling
It is important to remember that an individual affected by a heritable condition may have a homozygous recessive trait. Thus, the ophthalmologist should search for parental consanguinity or ambiguous parentage (nonpaternity, incest, occult adoption) or for a new mutation and should inquire about advanced paternal (or maternal grandparental) age. Heterogeneity may complicate the diagnosis. Somatic mutations also occur, as with segmental neurofibromatosis or unilateral unifocal retinoblastoma. Nonpenetrance or mild expressivity in other family members should be excluded through diligent examination. Chromosomal abnormalities and phenocopies caused by infections or drugs may account for the isolated affected person. Nonetheless, the ophthalmologist’s obligation to explain the disorder begins with an accurate diagnosis and establishment of the mode of heritability.
The genetic counseling process is nondirective; the genetic counselor informs rather than advises. It is inappropriate, perhaps even unethical, for a counselor to tell the patient what to do (eg, not to have any children). Counselors recognize the ability of individuals and families to make appropriate decisions for themselves concerning their own health and reproductive choices in accordance with their personal beliefs and opinions, and they support them in the decision-making process.
In some instances, genetic testing for ocular disorders may provide individuals with information about their specific genetic mutation. While such testing can assist in the diagnosis and potentially give patients options to participate in clinical trials of new treatments, it may also identify carrier status and mutations in asymptomatic individuals who have known familial mutations, facilitating early diagnosis and subsequent intervention when available. The implications of these results require careful consideration and counseling, because the information can affect not just the individuals who underwent testing but other family members as well. Genetic testing requests need to be carefully evaluated for compliance with existing guidelines and position statements covering the related ethical issues. For example, genetic testing for an adult-onset condition in a child, on the parents’ request when there is no immediate medical benefit for the child, is not indicated.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.