Genetic Counseling

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:

• Accurate diagnosis: To derive an accurate and specific diagnosis, the physician must be sufficiently aware of the range of human ocular pathology.

  • It is impossible to counsel or refer patients on the basis of “congenital nystagmus” or “color blindness” or “macular degeneration”; these are signs, not diagnoses.

• Complete family history: A family history will narrow the choices of possible inheritance patterns, but it may not necessarily exclude new mutational events, isolated occurrences of recessive diseases, and chromosomal rearrangements in individual circumstances.

  • The ophthalmologist should examine (or arrange to have examined) the parents, siblings, and other family members for mild manifestations of dominant diseases or characteristic carrier states in X-linked disorders.

  • Only an ophthalmologist will be cognizant of, and attentive to, the atypical findings of hereditary ocular disorders. For example, identification of 1 young adult with the findings of Usher syndrome—prelingual deafness; night blindness; visual field constriction; and, ultimately, deterioration of central vision—obligates the ophthalmologist to evaluate a younger sibling who is congenitally deaf but “historically” has no eye problems. The probability is very high that the sibling has the same disease.

• Understanding of the genetic and clinical aspects of the disorder: The ophthalmologist should appreciate, perhaps more intimately than any other physician, how some clinically similar diseases inherited in the same pattern may be the result of different and even nonallelic defects. For example, the visual implications of, and prognoses for, tyrosinase-positive and tyrosinase-negative oculocutaneous albinism are considerably different.

  • Ocular albinism is an X-linked trait and very rare in females.

  • Some entities that are clinically similar may be inherited differently and thus have a different impact on various family members.

  • In another example, pseudoxanthoma elasticum in both its autosomal dominant and recessive modes is often a late-onset disease that has serious implications for cardiovascular disease, stroke, and gastrointestinal bleeding. Informed counseling falls short if the ophthalmologist advises an affected patient only about visual disability associated with angioid streaks without attention to the complete disease and the risks to other family members.