Cone ERG subnormality to red flash in central retinal vein occlusion: a predictor of ocular neovascularisation?

In patients with unilateral central retinal vein occlusion (CRVO), we retrospectively examined whether cone electroretinogram (ERG) subnormality to red flash (ratio of the b-wave amplitude in the CRVO eye to that in the normal fellow eye < 1) found at the time of diagnosis of the CRVO was a predictor of later ocular neovascularisation. Ganzfeld ERG cone and rod responses had initially been obtained in a consecutive series of 21 patients with unilateral CRVO. Patients were re-evaluated 6-55 months later to determine whether ocular neovascularisation had developed. Of the 21 CRVO eyes, 6 (29%) were subnormal to red in the affected compared with the normal fellow eye. At follow-up, all 6 (100%) patients had developed ocular neovascularisation compared with 1 (7%) of the 15 patients who were supernormal to red (p = 0.00013). Cone ERG subnormality to red flash in CRVO eyes compared with normal fellow eyes may be a predictor of later development of ocular neovascularisation.