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Paula Y. Sacai, Adriana Berezovsky, Nivea N. Cavascan, Solange R. Salomao; Grating Acuity Deficit Measured by Sweep-VEP in Preverbal/Non-verbal Children with Nystagmus. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1571.
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Childhood nystagmus can be either isolated or associated with ocular and/or neurological disorders. The fixation instability caused by nystagmus directly contributes to decreased visual acuity. This study aimed to investigate grating acuity deficits (GAD) measured by the sweep visual evoked potentials technique (sweep-VEP) in preverbal and non-verbal children with nystagmus.
A consecutive group of 296 children with nystagmus (161 males - 54%), with ages ranging from 2 months to 141 months (mean=24.9±28.0, median= 13.9), had their grating acuity assessed by sweep-VEP. Nystagmus cases were assigned into one of the following categories: 19 (6.4%) isolated (normal fundus, no neurological disease, with or without strabismus/amblyopia); 125 (42.2%) with ocular diseases (albinism, Leber’s amaurosis, cone dystrophy, aniridia, bilateral cataracts, ROP, optic nerve hypoplasia etc); 103 (34.8%) with cortical visual impairment (CVI) and 49 (16.6%) with a combination of neurological and ocular conditions. GAD was calculated in logMAR by subtracting acuity thresholds from mean visual acuity value using age norms from our own laboratory. Two age groups were assembled: children <24 mos. (N=207) and children ≥24 mos. (N=89). One-way analysis of variance (ANOVA) was used to compare GAD among the four categories. The t-test was used to compare GAD between younger and older children within each of the four categories.
GAD was significantly more severe (p<0.05) in the CVI group (mean=0.79±0.26) when compared to the combined (mean=0.65±0.28), to the ocular (mean=0.54±0.31) and to the isolated (0.22±0.21) groups. Both for the younger[y] and older[o] age groups, the isolated nystagmus group had significantly smaller (P<0.05) GAD (mean[y]=0.19±0.22; mean[o]=0.31±0.17) when compared to ocular group (mean[y]=0.49±0.29; mean[o]=0.71±0.31), to the combined group (mean[y]=0.57±0.26; mean[o]=0.85±0.25) and to the CVI group (mean[y]=0.74±0.22; mean[o]=0.85±0.30). Significantly larger GADs (P<0.05) were found in the older group when compared to the younger for ocular, CVI and combined categories.
Deficits in grating acuity were detected in children with nystagmus regardless its main etiological cause (isolated, ocular and/or neurological conditions). More severe deficits in older children might be due to delays in diagnosis and treatment of their baseline conditions.
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