Comparison of Functional Impairment Using Multifocal Visual Evoked Potentials (mfVEP) and Frequency Doubling Perimetry (FDT–2)

Abstract

Abstract: : Purpose: To compare visual function abnormalities detected by mfVEP and FDT–2 testing. Methods: Fifteen patients with glaucomatous optic neuropathy were enrolled; 10 patients without an achromatic automated perimetry (AAP) defect, and 5 patients with a defect were identified. Glaucomatous optic neuropathy (GON) was defined as cup/disc asymmetry ≥0.2, peripapillary nerve fiber layer defect, or focal rim thinning, notching, or excavation. A visual field was defined as abnormal if the glaucoma hemifield test (GHT) was outside normal limits and there was a cluster of 3 contiguous abnormal points on the pattern deviation plot, with at least 1 point at the p<0.005 level. All patients underwent AAP (SITA–standard, program 24–2), frequency doubling perimetry (FDT–2, program N–24 threshold), and mfVEP testing. The mfVEPs were obtained using VERIS (EDI), three channels of recording, and monocular/interocular probability plots analyzed with custom software (1,2). For the mfVEP and FDT–2 tests, a hemifield was defined as abnormal if 2 or more contiguous points had p<0.01, or if 3 or more contiguous points had p<0.05 with at least one of these points with p<0.01. Results: The 5 patients (20 hemifields) with AAP defects had a total of 11 abnormal hemifields. A FDT–2 abnormality was detected in 8/11 hemifields (72.7%) and a mfVEP abnormality in 9/11 hemifields (81.8%). When a FDT–2 abnormality was detected, there was a corresponding mfVEP abnormality in 7/9 (77.8%) hemifields. When a mfVEP abnormality was noted, there was a corresponding FDT–2 defect in 7/11 (63.6%) hemifields. In the 10 patients without an AAP defect, a FDT–2 abnormality was noted in 10/40 (25.0%) hemifields and a mfVEP abnormality was noted in 17/40 (42.5%) hemifields. There was agreement for both tests for 27/40 (67.5%) hemifields. Conclusions: FDT–2 and mfVEP tests can detect visual field abnormalities when AAP shows no defect. There was good agreement among the measures for eyes with an AAP defect. There was modest agreement between FDT–2 and mfVEP for eyes without AAP defects. 1. Hood et al (2002) AO. 2. Hood and Greenstein (2003) Prog Ret Eye Res.

Keywords: visual fields • electrophysiology: clinical • detection