Electroretinography in central retinal vein occlusion. Correlation of electroretinographic changes with pupillary abnormalities.

In 149 eyes with central retinal vein occlusion (CRVO), we prospectively investigated the role of routine, clinical electroretinography (ERG) in differentiating ischemic (60 eyes) from nonischemic CRVO (89 eyes). Single-flash photopic and scotopic ERGs were recorded. Data for the amplitudes and implicit times of a- and b-waves and for the b-/a-wave amplitude ratio were analyzed in detail. The study revealed that the best ERG parameter (for both photopic and scotopic ERG) for differentiating ischemic from nonischemic CRVO was a subnormal b-wave amplitude (reduced to less than or equal to 60% or by greater than or equal to 1 SD from the normal mean value, or less than or equal to 64%-69% of that in the fellow normal eye), with a sensitivity of 80%-90% and a specificity of 70%-80%. ERG findings were correlated with the relative afferent pupillary defect (RAPD). An RAPD of greater than or equal to 0.7 log units showed a sensitivity of 88% and a specificity of 90% in differentiating ischemic from nonischemic CRVO. ERG and RAPD findings showed a good correlation. The combined ERG and RAPD tests could differentiate 97%-100% of ischemic from nonischemic CRVO cases, with a specificity of about 70%.