Clinical heterogeneity of dominant optic atrophy : the contribution of visual function investigations to diagnosis

The variability of the visual function impairment in dominant optic atrophy (DOA) makes it difficult to diagnose the disease within genealogies. Physiologic investigations were conducted on a family with DOA to evaluate methods of detecting clinical and subclinical signs in obligate heterozygotes, in order to identify affected subjects within the genealogy and to formulate the individual and reproductive risks. Investigations included tests for color vision, contrast sensitivity function (CSF), kinetic and static computerized perimetry, transient pattern reversal visual evoked potentials (VEPs) and steady-state flash VEPs. Eight subjects from the pedigree were diagnosed as having DOA. Two of them were unaware of their affection, and six showed wide clinical variability. CSF paralleled the central visual impairment, but was also slightly impaired in the two unaware subjects. Static computerized perimetry disclosed mild sensitivity defects in the central visual fields in these two patients. VEPs showed heterogeneous results as well, ranging from normal findings to severely altered tracings. This investigation suggests that combined clinical and functional evaluation is necessary to diagnose DOA. Particularly, the combined use of computerized perimetry, CSF, and VEPs allowed the identification of cases at a subclinical stage.