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V. C. Greenstein, H. M. Eggers, A. S. Wenick, D. C. Hood; Multifocal Visual Evoked Potentials in Strabismic Amblyopes: Decreased Amplitudes and Shortened Latencies. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4890.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate how strabismic amblyopia affects the amplitude and latency of the multifocal visual evoked potential (mfVEP).
Twelve patients (19-70 yrs) with strabismic amblyopia were enrolled in the study. Ten had esotropia, one consecutive exotropia and one orthotropia. Visual acuity in the amblyopic eye ranged from log MAR 0.3 to 1.3. Fixation was evaluated using micro-perimetry and visuoscopy. Monocular mfVEPs were obtained from each eye using a 60 sector, pattern-reversal dartboard array (44.5 deg ). Recording electrodes were placed at the inion (I) and I+4 cm, and at two lateral locations up 1 cm and over 4 cm from I. Monocular and interocular analyses of amplitude and latency were performed and probability plots were derived [1-3]; results were compared to 100 normal controls . A mfVEP hemifield was defined as abnormal based on the following cluster test: if 2 or more contiguous points had p<0.01, or 3 or more contiguous points had p<0.05 and at least one of these points had p<0.01.
Ten patients had steady to unsteady foveal fixation, and 2 patients with log MAR 1.0 and 0.7 had unsteady eccentric fixation 1-2 deg. nasal to the fovea. For the mfVEP, 11 amblyopic eyes and 6 fellow eyes had significant clusters of mfVEP responses with markedly decreased amplitudes. For 9 of the amblyopic eyes, both mfVEP hemifields were abnormal using the cluster test. Only one patient had normal mfVEP hemifields in the amblyopic eye (log MAR 0.2). Monocular latencies were significantly decreased (i.e. shortened) for amblyopic eyes compared to values for a group of 23 age-similar control eyes (P<.0001). Ten amblyopic eyes and 9 fellow eyes had decreased or shorter latencies. Only one of the amblyopic eyes, and 3 of the fellow eyes showed an increase in latency.
The mfVEP, which primarily reflects activity in V1, reveals visual field deficits in the amblyopic and fellow eyes of strabismic amblyopes and a paradoxical shortening of response latency.1. Hood et al. 2002, AO; 2. Hood and Greenstein 2003, PRER; 3. Hood et al. 2005, DOOP; 4. Fortune et al. 2004, DOOP.
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