Neovascularization in central retinal vein occlusion: electroretinographic findings
M. A. Johnson, S. Marcus, M. J. Elman and T. J. McPhee
Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Electroretinograms (ERGs) were measured in 15 patients with central retinal
vein occlusion (CRVO). Seven of the patients had neovascularization of the
iris (NVI) at the time of testing, and two developed NVI within one month
of testing; six did not have NVI or any other form of neovascularization
(NV) and were no longer considered to be at risk for NV from their present
occlusion. The ERGs were recorded as a function of the stimulus intensity
and to a 30-Hz flickering stimulus. A Naka-Rushton-type function was fit to
b-wave amplitudes, measured as a function of stimulus intensity, to
evaluate changes in ERG amplitude and sensitivity. Compared with eyes in
the no-NV group, eyes developing NVI had significantly reduced ERG
sensitivity and amplitudes. The distributions of sensitivity values in
these two groups did not overlap. All of the eyes with NV showed large a-
and b-wave and 30-Hz implicit time delays, but only one eye had a b/a-wave
amplitude ratio close to or less than 1. A comparison of ERG sensitivity,
amplitude data, and flicker timing data with retinal fluorescein
angiography in a two-alternative forced-choice analysis showed that ERG
sensitivity and amplitude loss were better than retinal fluorescein
angiography at discriminating eyes with CRVO and NVI from eyes with CRVO
without NVI.
