Branch retinal vein occlusion decreases the potential of the inner retinal layer.

To identify the affected retinal layer in cases of branch retinal vein occlusion (BRVO), we analyzed the scotopic electroretinogram (ERG) and electrooculogram (EOG) obtained on the same day in 30 patients with unilateral BRVO. Patients with eye diseases other than unilateral BRVO were excluded. A dome-shaped Ganzfeld illuminator was used for scotopic ERG stimulation and EOG illumination under conventional recording conditions. There was no significant difference in the mean values of scotopic ERG variables between the eyes with BRVO and the normal eyes, but the EOG light peak and L/D ratio were significantly lower in the eyes with BRVO (p < 0.05). However, there was no significant difference between eyes with BRVO and normal eyes regarding the dark through value. Since the light rise potential is induced by background illumination, the low values for light peak and L/D ratio in the eyes with BRVO represent a decrease in the light rise potential compared with that of normal eyes. In addition, since the b wave amplitude of the ERG was normal in the eyes with BRVO, the scotopic ERG and EOG tests suggest that generalized mild hypoxia affects the inner retinal layer of the eyes with BRVO.