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L. F. Kehler, L. A. Fraine, P. H. Derr, D. Lepone, J. Patel, S. P. Donahue; An Office-Based System for Measuring Transient Pattern Reversal Visually Evoked Potentials in Children. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5892.
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Visual-evoked potentials (VEP) are used to quantify normal and abnormal visual function in children. However, most VEP techniques require substantial test time and a laboratory setting, making routine testing of young children with suspected visual system dysfunction extremely challenging. We have adapted this technology to produce a user- and patient- friendly, PC-linked system for measuring transient pattern reversal VEPs (prVEPs) in the office setting.
Thirty children aged 2-12 years with normal visual systems (uncorrected visual acuity 20/25 OU, no significant refractive error or strabismus, normal anterior and posterior segments; n=15) or known visual deficits from refractive error, amblyopia, or structural abnormalities were tested. Synchronized single-channel transient prVEPs were recorded with a modified Diopsys Enfant System (Diopsys, Inc., Pine Brook, New Jersey, USA), using three gold cup scalp electrodes, and the filtered N75-P100-N135 complex was analyzed. Children with strabismic or anisometropic amblyopia were tested with and without correction. In some children, anisometropia and uncorrected refractive error were simulated by blurring one eye to a known acuity using plus lenses. Children were tested using 5 and 10 sec stimuli at 3 various checkerboard sizes (84, 42, and 10 min of visual arc; approximate acuities 20/280, 20/140, and 20/35). Each eye was tested individually, and the test repeated with both eyes open.
In normal children, detectable standard VEP responses (mean amplitude 11.1-13.4 uV) with measureable N75 and P100 waveforms were produced using test protocols as short as 5 seconds and did not change measurably with check size. Ten-second test periods had less variability in older children, while a longer test time did not improve variability in younger children. Latencies increased nominally from 97 to 109 msec with smaller check sizes.
Transient pattern reversal VEPs that correlate well with visual function can be reliably obtained in children in the office setting using the Enfant System and this modification. Ophthalmologic applications include office diagnosis of visual dysfunction in preverbal children, monitoring visual improvement during treatment, and screening for visual system abnormalities.
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