Which finding in the ERG trace would indicate the presence of progressive retinal atrophy?

The presence of progressive retinal atrophy (PRA) is characterized by the degeneration of the photoreceptors in the retina, particularly the rod and cone cells. In an electroretinogram (ERG), which measures the electrical responses of various retinal cell types to light stimulation, a reduced amplitude of the response indicates that the functionality of these photoreceptors is compromised.

In cases of PRA, the decreased amplitude reflects a diminished ability of the retina to respond to light due to the loss of photoreceptors. As the condition progresses, the amplitude of the ERG trace tends to further decline, corroborating the diagnosis of PRA. Therefore, identifying a reduced amplitude on the ERG is significant for diagnosing this specific retinal condition, as it directly correlates with the extent of photoreceptor degeneration.

Normal or high amplitude would suggest intact retinal cells, while fluctuating amplitude may indicate other types of retinal issues rather than progressive retinal atrophy. Thus, the finding of reduced amplitude is a clear indication of the presence of PRA.