Reliability of the Implicit Time of Flicker Erg B-Wave as an Objective Diagnostic Tool for Retinopathies

Flicker ERG represents an objective method to evaluate photoreceptors functional state. Aim of the present work was to assess which of its two parameters – implicit time or amplitude – could better discriminate between normal and pathologic subjects affected by different types of retinopathies. Two groups of patients were enrolled. The first group included 34 eyes of 17 patients with no eye pathologies; the second group included 23 eyes of 12 patients with different retinopathies. The Retimax Advanced Plus® was used to generate a flash, the intensity of which was calibrated according to the ISCEV standard. Both the implicit time and the amplitude of the flicker ERG B wave were recorded, and related to the pathological state of the retina. The average value of the amplitude was significantly decreased in retinopathic patients (29.42 ± 12.05 mV) with respect to normal patients (53.57 ± 19.24 mV), however with a high variability and a wide zone of overlapping between normal and pathologic patients. Implicit time values had a much lower variability, with no overlapping between the two groups of patients: average normal values were 31.70 ± 1.40 ms for healthy patients and 39.48 ± 2.13 ms for retinopathic patients. Our results indicate that the implicit time value of the flicker ERG B-wave can be a quantifiable objective measurement of photoreceptor damage in different types of retinal diseases. Therefore, it can be a valuable alternative for their diagnosis and follow up, which nowadays is still mainly based on morphologic criteria.