Visual Processing Lab
(Sektion für klinische und experimentelle Sinnesphysiologie)

Johann-Joachim Flechner
Universitäts-Augenklinik
Leipziger Str. 44
39120 Magdeburg
Germany
joachim.flechner@student.uni-magdeburg.de


I am a medical student doing my doctoral thesis in the Visual Processing Lab and investigate the visual system with multifocal ERG- and VEP- recordings. Please find a brief summary of my findings in the abstract below.


Slow pattern-reversal stimulation facilitates visual field testing with mfPERG

Purpose: The use of the multifocal pattern electro-retinogram (mfPERG) for objective visual field testing is critically impaired by the small response amplitudes obtained. Therefore it was tested whether multifocal visual evoked potentials (mfVEPs) and mfPERG responses are enhanced for multifocal stimulation sequences that are slower than standard sequences. Further the responses for two different stimulation modes, namely pattern-reversal (PR) and pattern-onset (PO), were compared.

Methods: Using VERIS Science 5.1.10X (EDI, Ca, USA) we simultaneously recorded mfVEPs and mfPERGs in three different experiments stimulating at 52 separate locations comprising a visual field of 44 diameter. (1) We compared response-magnitudes to three PR- and two PO-conditions, which differed in their maximal stimulation rate. (2) We compared for equal recording durations the signal-to-noise-ratios (SNR) of four PR stimuli with different stimulation rates. (3) We assessed the efficacy of the optimal mfPERG-PR stimulus in the detection of a simulated visual field defect.

Results: (1) Both mfPERGs and mfVEPs were substantially enhanced for lower stimulation rates. The greatest effects were obtained for the mfPERG-N95 to slow pattern-reversal stimulation, which was increased by a factor of 5.20.6 compared to that for the standard condition. (2) Highest mfPERG-SNRs were obtained for a PR stimulus reverting its contrast with a probability of 50% every 53 ms. (3) mfPERG-based detection of simulated visual field defects with slow pattern-reversal yielded a median sensitivity and specificity of 96.2% and 100%, respectively. Within the central 17.5 of the visual field the respective values for mfVEPs were 95% and 92.5%.

Conclusions: The enhancement of both mfPERGs and mfVEPs for slow stimulation suggests that the underlying mechanisms are of retinal origin. Pattern-reversal stimulation with a contrast-reversal probability of 50% every 53 ms allows for simultaneous high-resolution mfPERG- and mfVEP-based visual field testing and thus helps to investigate how retinal ganglion cell dysfunction is related visual field defects.
Last update by Michael Hoffmann 03.09.2013