![]() mfERG waveforms illustrate the classic appearance of hydroxychloroquine toxicity with a severe depression of the paracentral waveforms. A 73-year-old asymptomatic female with an eight-year history of hydroxychloroquine use (at 7.5 mg/kg/day) presents with acuity of 20/20, a normal fundus appearance, Amsler grid and color vision. Using a cross-correlation technique, the software determines the retinal response from each of the 103 segments of the retina.įigure 2. ![]() They all follow the same pseudorandom sequence, with each hexagon starting at a slightly different position in this sequence. During stimulation the hexagons on the screen independently change every 13 milliseconds. The resulting electrical activity is recorded by an electrode, then amplified and analyzed. During multifocal ERG testing, the patient views a rapidly changing sequence on the monitor. A typical multifocal ERG protocol takes about 20 minutes to complete both eyes individually. The hardware is united by VERIS software (Electro-Diagnostic Inc., San Mateo, Calif.). While we have used it to confirm non-organic visual loss, we have found it more relevant in the diagnosis of focal cone dystrophy and other similar disorders where mfERG is often the only abnormal test.Ī typical multifocal ERG recording requires electrodes, an amplifier, a computer, a stimulating monitor and a monitoring camera. We find it most useful in assessing patients with visual acuity loss and a dearth of clinical findings. This precision helps correlate electrophysiologic findings with visual field testing. Unlike the focal ERG, mfERG also indicates the precise distribution of the retinal dysfunction. In general, an abnormal mfERG indicates that the foveal cones and/or bipolar cell layers are dysfunctional and the source of vision loss. determination of hydroxychloroquine toxicity (Plaquenil toxicity).distinguishing between optic nerve and retinal disease and.We have found mfERG most useful in the diagnosis of : For ease of pattern recognition, the software then generates a3-D waveform of the response density reflecting a much higher response in the normal foveal center. Using a cross-correlationtechnique, the software determines the electrical response of each of 131 segments in the posterior pole. The patient views a monitor displaying a rapidly changing sequence of hexagons. The typical mfERG setup includes a contact lens electrode on the cornea connected to an electrically isolated amplifier. We describe the principles behind this new technology and present clinical examples so that the reader can better understand when to refer a patient for this specialized testing.įigure 1. This test helps us discriminate between optic-nerve and retinal disease, detect early hydroxychloroquine toxicity, diagnose and distinguish between the various white dot syndromes and follow patients with inherited retinal diseases who have extinguished Ganzfeld ERGs. ![]() Multifocal electroretinography (mfERG) is most useful in solving the common puzzle of a patient with poor vision who has a normal appearing retina. ![]()
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