Individual components of the ERG waveform (a-wave, composite b - wave,
cone b - wave
and rod b - wave) reveal
relative contributions of different retinal cells to the overall functional activity of the retina.
If the disease is uncommon, as with the progressive
rod -
cone degeneration (PRCD) form of Progressive Retinal Atrophy in Australian Shepherds, or if use of a test
and careful breeding decisions have markedly reduced the frequency of a formerly common mutation (think what could be done with CEA in Collies,) testing could then be confined to only those dogs with known family history of the disease or with
relatives that have been DNA tested as carriers.