Attitudes to predictive DNA testing for myocilin glaucoma: experience with a large Australian family

Glaucoma is a major cause of visual impairment and blindness in developed countries. Half of those with glaucoma are unaware that they have the disease. Mutations in the myocilin (MYOC) gene are responsible for 3 to 5% of primary open angle glaucoma, thus predictive DNA testing in family members of some glaucoma pedigrees is possible. We wished to determine the attitudes of affected and unaffected family members to the use of predictive DNA testing in glaucoma.

We surveyed the attitudes of family members from one such pedigree to determine the acceptability of predictive DNA testing. We studied 72 members of a large family in which the MYOC mutation, THR377MET, segregates. Family members were examined over an 8-year period as part of research initiated to identify the gene. Once the mutation was identified, we offered participants the result of their DNA test after a genetic counseling session. Family members were subsequently given a questionnaire about the counseling and DNA result.

Most wished to know their result after counseling; 26 of 27 (96%) felt the genetic counseling session was necessary, but participants' attitudes varied as to whether they preferred this in person, by phone, or letter. Forty three patients were resurveyed 5 years after their initial counseling session. No adverse problems relating to the predictive testing were reported, though two had been asked about DNA testing by insurance companies; 5 of 24 (21%) individuals who had been informed they did not carry the mutation were unsure if they carried the mutation 5 years after counseling, while all 19 mutation carriers (who were being examined annually) correctly recalled their mutation status.

This study suggests that predictive glaucoma testing in appropriate circumstances is acceptable to patients and their families.