Deficits in the electroretinogram in neovascular age-related macular degeneration and changes during photodynamic therapy

Abstract

To describe the deficits in four electroretinography (ERG) modalities in patients with neovascular age-related macular degeneration (AMD). To describe the changes in these parameters during a course of verteporfin photodynamic therapy (PDT). Pattern (PERG), multifocal (mfERG) (19 segment simplified test protocol), flash ERG and flicker ERG were performed in patients with active neovascular AMD before PDT and compared to fellow eye controls using paired t-tests. Changes in ERG parameters during the 12 month treatment course were visualised using 95% confidence intervals of the median difference. The statistical significance of any changes was quantified using Wilcoxon signed ranks tests. Fifty patients were recruited and followed. At presentation all ERG amplitudes were reduced with greater reductions in focal as opposed to global test protocols (P < 0.05). Over the 12 month course of PDT, PERG P50 amplitude showed a general downward trend and latency remained unchanged. mfERG p1 amplitude density showed an upward trend at six months before returning to baseline by 12 months. mfERG ring 2 amplitude density was significantly increased at 12 months compared to baseline (P = 0.010). Flicker ERG latency was significantly increased at six months compared to baseline (P = 0.015). The simplified mfERG protocol was tolerated by this patient group, however, they found the full test protocol demanding. Large deficits in the retinal ERG function occur in neovascular AMD and involve retinal locations adjacent to as well as overlying choroidal neovascularisation (CNV). After PDT there is an improvement in electro-retinal function in retinal locations overlying the CNV.