BACKGROUND: In order to assess the influence of optical factors on the multifocal visual evoked potential (mfVEP), we obtained mfVEPs with optimal refraction and compared them to recordings with various degrees of dioptrical defocus. METHODS: Monocular mfVEPs were recorded from the right eye in eight normal subjects. Dartboard stimuli with 60 sectors arranged in six concentric annuli spanning 60 degrees were generated with a VERIS system and presented on a computer monitor. Two pairs of electrodes were placed 3 cm above and below and 3 cm to the right and left of the inion. Two sets of mfVEP records per subject were obtained, one with best-corrected visual acuity and another when the stimulus was defocused by +1.0, +2.0 or +3.0 D. A signal-to-noise ratio (SNR) measure was calculated for every response from the two channels. RESULTS: The effect of defocus depended on eccentricity: when defocus was at +2.0 D and higher, reducing visual acuity to <0.3, the central mfVEP responses were reduced to approximately 60%, while defocus had no marked effect at eccentricities >7 degrees. CONCLUSIONS: The results suggest that, in contrast to the mfERG, the mfVEP requires optimal refraction to correctly assess the cortical responses.
BACKGROUND: In order to assess the influence of optical factors on the multifocal visual evoked potential (mfVEP), we obtained mfVEPs with optimal refraction and compared them to recordings with various degrees of dioptrical defocus. METHODS: Monocular mfVEPs were recorded from the right eye in eight normal subjects. Dartboard stimuli with 60 sectors arranged in six concentric annuli spanning 60 degrees were generated with a VERIS system and presented on a computer monitor. Two pairs of electrodes were placed 3 cm above and below and 3 cm to the right and left of the inion. Two sets of mfVEP records per subject were obtained, one with best-corrected visual acuity and another when the stimulus was defocused by +1.0, +2.0 or +3.0 D. A signal-to-noise ratio (SNR) measure was calculated for every response from the two channels. RESULTS: The effect of defocus depended on eccentricity: when defocus was at +2.0 D and higher, reducing visual acuity to <0.3, the central mfVEP responses were reduced to approximately 60%, while defocus had no marked effect at eccentricities >7 degrees. CONCLUSIONS: The results suggest that, in contrast to the mfERG, the mfVEP requires optimal refraction to correctly assess the cortical responses.
Authors: Paulo Fernandes; Cesarina Ferreira; Joana Domingues; Ana Amorim-de-Sousa; Miguel Faria-Ribeiro; António Queirós; José M González-Meijome Journal: Doc Ophthalmol Date: 2022-04-02 Impact factor: 1.854
Authors: Wendy W Harrison; Marcus A Bearse; Jason S Ng; Shirin Barez; Marilyn E Schneck; Anthony J Adams Journal: Doc Ophthalmol Date: 2009-03-26 Impact factor: 2.379
Authors: Jacob Lahr; Jessica Peter; Michael Bach; Irina Mader; Christoph Nissen; Claus Normann; Christoph P Kaller; Stefan Klöppel Journal: Front Hum Neurosci Date: 2014-09-08 Impact factor: 3.169