Multifocal Electroretinography Deficits in Neovascular Age Related Macular Degeneration

Abstract

Abstract: : Purpose: Subfoveal choroidal neovascularisation (CNV) is a major cause of visual loss in age–related macular degeneration (AMD) but the impact on specific function within the retina remains unclear. This study investigates the functional deficits in the multifocal ERG in eyes with neovascular AMD compared to age–matched controls. Methods:New patients attending a regional medical retina service with active subfoveal predominantly classic CNV secondary to AMD were recruited and the affected eye studied (CNV group). Patients attending for treatment of CNV secondary to AMD were recruited and their fellow eyes studied as controls if these eyes had no CNV and normal visual acuity and the patient was age matched (control group). Function was tested by refraction protocol logMAR visual acuity (VA) recorded at 1 metre, contrast sensitivity (Pelli–Robson), and multifocal electroretinography (mfERG). 19 segment mfERGs over the central 20 degrees (radius) were recorded using a Roland Consult Retiscan system and DTL thread electrodes. First order mfERG responses were described by the P1 amplitude of three rings. Each parameter was quantified within groups using the median and 95% confidence intervals. A Mann Whitney U test for independent groups was used to compare parameters between groups. Results:16 eyes were recruited to the CNV group and 14 controls. The two groups were age matched (median age: CNV 77.8 years, control 77.7 years). Visual acuity, contrast sensitivity and mfERG ring 1 amplitude were all significantly reduced in the CNV group compared to the control group (p<0.05). There was no significant difference in mfERG amplitude in rings 2 and 3 between CNV and control groups. In the CNV group there was no significant association between VA or CS and mfERG amplitude in any ring. Conclusion: As described by previous studies (Palmowski et al. 2002, Huang et al. 2000), mfERGs are reduced in the central retinal region in patients with predominantly classic CNV secondary to AMD. However pre–treatment mfERG deficits do not appear to be correlated with VA or contrast sensitivity. The value of mfERG as a predictor of treatment outcome and its relationship to other measures of retinal function requires further study.

Keywords: age–related macular degeneration • electroretinography: clinical • choroid: neovascularization