Light rise of the EOG compared with light rise of the photopic flash ERG

Abstract

Abstract: : Purpose:To determine if the magnitude of the rise in B–wave amplitude of the ISCEV standard flash photopic ERG occurring during light adaptation is related to the light rise in the corneo–retinal potential as seen in the standard EOG procedure, in a variety of pathological disorders usually investigated by EOG/ERG. Methods:17 subjects referred for electro–diagnostic tests including EOG/ERG, had the standard photopic flash ERG performed twice, once at the end of the EOG procedure (after 15 minutes light adaptation) at 68cd/m², and again after 20 minutes dark adaptation. Provisional diagnoses for these subjects included retinitis pigmentosa (6), Usher’s syndrome (2), adult vitelliform dystrophy (2), CSNB (1), pattern dystrophy (1), toxic retinopathy (1), none (4) (of which 2 had nyctalopia, 1 constricted field, 1 poor VA). For each eye the ratio of the photopic ERG B–wave amplitude after light adaptation, to the amplitude before adaptation was calculated (ERG light rise), and compared with the EOG light rise (Arden ratio) for the same eye. Results:ERG light rises had a mean ratio of 2.12 (SD 0.72 range 1.0–4.1), and EOG light rise had a mean Arden ratio of 1.72 (SD 0.43 range 1.0–2.4). However, there was no significant correlation between the two ratios (Pearson coefficient r² = 0.015). Interestingly, two subjects had no ERG light rise, even though there was an EOG light rise, albeit subnormal (∼1.4). Conclusions:The rise in photopic ERG B–wave amplitude occurring during light adaptation appears to be independent of the EOG light rise, suggesting different underlying physiological mechanisms.

Keywords: electroretinography: clinical • electrophysiology: clinical • retinal pigment epithelium