Objective visual field determination in forensic ophthalmology with an optimized 4-channel multifocal VEP perimetry system: A case report of a patient with retinitis pigmentosa

Department of Ophthalmology, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054, Erlangen, Germany.
Documenta Ophthalmologica (Impact Factor: 1.63). 08/2011; 123(2):121-5. DOI: 10.1007/s10633-011-9283-0
Source: PubMed


We present the case of a 59-year-old male patient with progressive vision impairment and consecutive visual field narrowing ("tunnel view") for 7 years and a known retinitis pigmentosa for 5 years. The remaining Goldmann perimetric visual field at time reported was less than 5°. A request for blindness-related social benefits was rejected because an ophthalmologic expert assessment suggested malingering. This prompted us to assess an objective determination of the visual field using multifocal VEPs. Objective visual field recordings were performed with a four-channel multifocal VEP-perimeter using 58 stimulus fields (pattern reversal dartboard stimulus configuration). The correlated signal data were processed using an off-line method. At each field, the recording from the channel with the maximal signal-to-noise ratio (SNR) was retained, thus resulting in an SNR optimized virtual recording. Analysis of VEP signals was performed for each single field and concentric rings and compared to an average response measured in five healthy subjects. Substantial VEP responses could be identified in three fields within the innermost ring (eccentricity, 1.7°) for both eyes, although SNR was generally low. More eccentric stimuli did not elicit reliable VEP responses. The mfVEP recording was correlated with perimetric visual field data. The current SNR optimization by using the channel with the largest SNR provides a good method to extract useful data from recordings and may be appropriate for the use in forensic ophthalmology.

Download full-text


Available from: Jan Kremers
  • [Show abstract] [Hide abstract]
    ABSTRACT: There is evidence that multifocal visual evoked potentials (VEPs) can be used as an objective tool to detect visual field loss. The aim of this study was to correlate multifocal VEP amplitudes with standard perimetry data and retinal nerve fibre layer (RNFL) thickness. Multifocal VEP recordings were performed with a four-channel electrode array using 58 stimulus fields (pattern reversal dartboard). For each field, the recording from the channel with maximal signal-to-noise ratio (SNR) was retained, resulting in an SNR optimised virtual recording. Correlation with RNFL thickness, measured with spectral domain optical coherence tomography and with standard perimetry, was performed for nerve fibre bundle related areas. The mean amplitudes in nerve fibre related areas were smaller in glaucoma patients than in normal subjects. The differences between both groups were most significant in mid-peripheral areas. Amplitudes in these areas were significantly correlated with corresponding RNFL thickness (Spearman R=0.76) and with standard perimetry (R=0.71). The multifocal VEP amplitude was correlated with perimetric visual field data and the RNFL thickness of the corresponding regions. This method of SNR optimisation is useful for extracting data from recordings and may be appropriate for objective assessment of visual function at different locations. This study has been registered at (NCT00494923).
    No preview · Article · Nov 2011 · The British journal of ophthalmology
  • [Show abstract] [Hide abstract]
    ABSTRACT: OBJECTIVE: To assess different effects of image degradation that could result from optic media opacities on multifocal retinal (mfERG) and cortical responses (mfVEP). METHODS: Monocular flash-mfERGs and pattern-reversal mfVEPs were recorded. MfERG-P1 amplitudes and implicit times and mfVEP root-mean-square values (RMS) and delays were compared for different filter conditions (none, 8% luminance, 50% luminance, 50% luminance plus blur) in a total of ten participants with normal vision. RESULTS: Reducing stimulus luminance down to 50% and 8% reduced mfERG amplitudes to 86% and 42%, respectively, with no significant effect on mfVEP amplitude. Implicit times were increased for mfERGs by 0.9ms and 6.0ms, respectively, and for mfVEPs by 1.0ms and 6.3ms, respectively. For '50% luminance plus blur' mfERG amplitudes were significantly reduced centrally and enhanced peripherally and delayed by 1.3ms. MfVEPs were reduced close to noise level independent of eccentricity. CONCLUSIONS: Degradation of the retinal image is a potential source of discrepancies between mfERGs and mfVEPs. Image blur suppresses the mfVEP at all locations and changes mfERG topography, resulting in a selective loss of central responses. SIGNIFICANCE: Considering optic media opacities is of importance for the correct interpretation of mfERG and mfVEP recordings, particularly in elderly patients.
    No preview · Article · Jan 2013 · Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Multifocal visual electrophysiology, consisting of multifocal electroretinography (mfERG) and multifocal visual evoked potential (mfVEP), can objectively evaluate retina function and retina-cortical conduction pathway status by stimulating many local retinal regions and obtaining each local response simultaneously. Having many advantages such as short testing time and high sensitivity, it has been widely used in clinical ophthalmology, especially in the diagnosis of retinal disease and glaucoma. It is a new objective technique in clinical forensic medicine involving visual function evaluation of ocular trauma in particular. This article summarizes the way of stimulation, the position of electrodes, the way of analysis, the visual function evaluation of mfERG and mfVEP, and discussed the value of multifocal visual electrophysiology in forensic medicine.
    No preview · Article · Aug 2013 · Fa yi xue za zhi
Show more