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D. Nagy, E. Zrenner, H. Jaegle; Direct Fundus-Controlled Multifocal ERG: First Evaluation of a Novel Technique. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5976.
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The multifocal electroretinogram (mfERG) was introduced into clinical application about 10 years ago and has been established as a useful diagnostic tool in retinal diseases. Still, there are limitations of its use due to - among others - technical problems, like monitoring of fixation. Here we present a novel technique, which combines a fundus camera with a stimulation screen allowing for fixation-controlled mfERG.
MfERGs were measured in ten healthy subjects (5 female and 5 male, mean age: 30, range: 14 to 46 years) using the direct fundus-controlled multifocal ERG (Roland Consult GmbH, Germany). The stimulating device was connected to a RetiPort system. ERGs were recorded twice from the right eye of every patient using a scaled stimulus array consisting of 7, 19, 37 or 61 hexagons covering a visual field of approx. 40x40 deg. Each recording was devided into segments, which were repeated on a subjective assessment of response quality. Responses were amplified (low pass: 10 Hz, high pass: 100 Hz) and analyzed according to ring averages of the first order kernel responses. Amplitude and implicit time were analyzed for each setting. Finally, fundus photographs were taken from each subject.
For all conditions normal response topographies were obtained. The P1 amplitude varied between 42.1 and 165.0 nV/deg2 in the central hexagon depending on the total number of hexagons in the stimulus and between 15.0 and 32.5 nV/deg2 in the outermost ring. The P1 implicit time changed from ca. 43.0 ms in the center to 37.4 ms in the outer ring and was similar for all recording conditions. We found significant variability in the response amplitude of the central hexagon between consecutive runs (difference between runs: 2.5 to 96.2%) but a good reproducibility for the outer rings. Smallest variability between repeated recordings was found for 61 hexagons.
Our study showed that the fundus-controlled multifocal ERG is a convenient and precise technique for monitoring fixation during measurement. Although we found a great variability of response amplitudes in the central hexagon, this may be improved in the future by head stabilization and automatic fixation detection. One major advantage of the system is the continuous fundus imaging while mfERGs are recorded, which makes it an ideal device for ERGs in patients with macular disease.
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