CONTROVERSIES IN OPHTHALMOLOGY Predictive DNA testing in ophthalmology

A28 year old man with retinitis pigmentosa (RP) presents with his 4 year old daughter who is afraid of the dark and is bed wetting. He would like his daughter to have a DNA test to determine whether she has RP. The man was diagnosed with RP at age 7 years after his parents noted nyctalopia and he had a confirmatory electroretinogram (ERG). The man’s father was diagnosed at age 30 years, while the man’s younger sister was diagnosed at age 5 years. The man also has a son age 7 years, who seems to have normal vision. None of the adults with RP had visual fields good enough to hold a driver’s licence. The pedigree is shown in Figure 1. With many patients aware of the publication of the human gene map, clinicians are frequently asked about DNA testing. Could we organise the DNA test? Which genes could we test? Where could it be done? How much would it cost? How accurate are the results? With any investigation we should ask “How will it change the management of the child?” Should we suggest using a night light or not? Are there any ethical concerns about doing the DNA test? Isn’t it simpler to organise an ERG?