A comparison of pattern and multifocal electroretinography in the evaluation of age-related macular degeneration and its treatment with photodynamic therapy

Abstract

This study compares pattern electroretinography (PERG) and multifocal electroretinography (mfERG) measures in 13 patients with predominantly classic choroidal neovascularisation (CNV) associated with age-related macular degeneration (ARMD, 9/13 unilateral, 4/13 bilateral), assesses the usefulness of each test in monitoring disease progression, and identifies electrophysiological predictors of outcome following treatment with photodynamic therapy (PDT). PERG and mfERGs were recorded at presentation, 2 weeks post-treatment, and at 3 monthly intervals for 2 years. The PERG was detectable in 8/13 patients with unilateral disease; the mfERG was detectable in 12/13 patients. P50 and N95 amplitudes increased in 6/8 patients and mfERG p1 increased in 7/13 patients at 2 years. PERG amplitudes correlated strongly with mfERG amplitudes in patients with unilateral disease. PERG P50 and mfERG p1 amplitude correlated with visual acuity at 2 years (R = 0.68, R = 0.82, respectively). The largest PERG P50 and mfERG p1 amplitude difference between treated and fellow eyes of all the groups on initial visit was associated with a poor visual outcome (P50 64% difference; p1 29% difference) whereas those with the smallest P50 and p1 amplitude difference was associated with improved vision at 2 years (P50 30% difference; p1 21% difference). The PERG and mfERG provide an objective measure of central retinal function in the progression of ARMD. A detectable PERG on presentation was the single best indicator of improved function and visual acuity at 2 years. The mfERG demonstrated disease progression from central retina into the paramacular regions over 2 years. Patients with poor visual outcomes had the largest inter-ocular amplitude difference on presentation, suggesting that such patients may have a worse prognosis following treatment.