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S Parks, D Keating, AL Evans; The Wide Field Multifocal ERG: A Review of 2151 Investigations . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1794.
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Purpose: Multifocal electroretinography is a powerful technique for imaging retinal function. However in routine clinical practice recordings can sometimes be difficult to perform and data sets can be compromised. This retrospective study reports the application of wide field multifocal electroretinography in clinical practice. Methods: In addition to conventional electrophysiology, 2151 wide field mfERG investigations were performed over a four-year period. A custom electrophysiological system was used to stimulate 90 degrees of the visual field. Wide field stimulation was achieved by using a digital polysilicon projection system. The stimulus array contained 61 empirically scaled hexagons (scaled with eccentricity to account for photoreceptor topography, photo-adaptive response profile and projection luminance gradient). Each hexagon alternated between black and white (97% contrast) controlled by a binary m-sequence. A maximum length sequence was chosen that when decimated would ensure orthogonality not only between elements but also between higher order contributions to degree three. An amplifier gain of 100,000 with an ADC digitisation rate of 1200Hz and a 4-channel dual high/low pass filter of 1-300 Hz and 10-100Hz were used. The recording period comprised sixteen intervals of 30 seconds providing a total recording time of 8 minutes. Real time analysis included a reliability index of incoming data based on the raw data source fluctuations, which scores the quality of the acquired data. A confirmed analysis cohort was assessed to provide details on the general tolerance of the investigation and in the improvements in diagnostic convergence over conventional electrophysiology. Results: Of the 2151 investigations 86 (4%) had reliability index in one or both eyes below the tolerance of 70%. 14 (0.6%) investigations were terminated before completion due to poor patient compliance. 1694 (79%) investigations confirmed or improved localisation of pathology to a retinal defect. 313 (15%) provided complementary information to discount an outer / mid retinal cause for visual dysfunction. In 44 (2%) investigations results remained inconclusive. Conclusion: Wide field multifocal electroretinography is well tolerated in a routine ophthalmic clinical service setting. In addition, these results indicate it is an important addition to the electrophysiological investigations available for the early detection and monitoring of visual dysfunction.
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