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Mei Ying Boon, Harry Leung, Catherine Suttle, Chi D Luu, Tiong Peng Yap, Stephen Hing; Suprathreshold VEPs as an indicator of abnormal cortical processing in nonstrabismic amblyopes. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4120.
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© ARVO (1962-2015); The Authors (2016-present)
Letter visual acuity(VA) is used to guide amblyopia management. Recurrence of, and persistent amblyopia after treatment indicates a need for a better means of assessing visual system status. Visual evoked potentials(VEPs) may allow better objective assessment of cortical abnormality/recovery during treatment than VA. We propose that an abnormal response to suprathreshold low spatial frequency stimuli may be a useful indicator of visual system abnormality. Thus, the purpose is to characterise VEPs in response to such stimuli in children with amblyopia.
Children with non-strabismic amblyopia and controls were recruited. Over 1-3 visits, at least 4 months apart, right(OD), left(OS) and binocular(OU) VEPs in response to suprathreshold stimuli (high contrast, 2 cycles per degree, sine-wave gratings, pattern onset/offset on a calibrated monitor) were recorded. Data were divided into groups based on the child’s VA and stage of recovery, in order of decreasing severity: bilateral (OD&OS>0.2 logMAR VA), unilateral (OD or OS>0.2), nearly recovered (OD&OS 0.08-<0.2), recovered (OD&OS≤0.06) amblyopes, controls (OD&OS≤0.06). To check if VEP component predicts group membership, ordinal logistic generalized estimating equations (GEEs) (dependent variable (DV):group, within-subjects variable:visit, predictors:VEP measures of C1, C2, C3 amplitude/latency, age) were run. To check for between group differences in VEP measures with controls as the reference group, linear GEEs (DV:VEP component, within-subjects variable:visit, predictors:group, age) were run.
18 bilateral (mean±SD 6.4±2.1 years old), 28 unilateral (6.7±1.4), 6 nearly recovered (5.7±0.9), 4 recovered (7.2±0.63) amblyopes and 11 controls (9.1±1.5) participated. Only OU C3 amplitude (Exp(β)=1.05, p=0.02) and age (Exp(β)=1.49, p=0.03) were predictors of being in a less severe group. Bilateral, unilateral, recovered amblyopia group membership were predictive of significantly lower C3 amplitude than controls (Fig. 1): Exp(β)=1.4E-6, p=0.02; Exp(β)=2.8E-7, p=0.004; Exp(β)=4.0E-8, p=0.005 respectively. Monocular and OU results were similar.
C3 amplitude is associated with age and severity of amblyopia. Bilateral, unilateral and recovered amblyopia are associated with lower C3 amplitudes than controls. Further research is required to understand why nearly recovered amblyopes had higher C3 amplitudes than recovered.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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