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W. V. Good, C. Hou, A. M. Norcia; Quantitative Assessment of Contrast Sensitivity in Young Children With Cortical Visual Impairment. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2492.
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© ARVO (1962-2015); The Authors (2016-present)
Cortical visual impairment (CVI) is the leading cause of bilateral vision impairment in children in Western countries. The effects of CVI on contrast sensitivity (CS) are unknown. The purpose of this study was to evaluate CS quantitatively in young children with CVI, compared with age-matched normal control children and with full term, healthy infants 5-7 months of age.
The sweep visual evoked potential was used to measure contrast sensitivity in 34 children (ages 5 months to 5 years) with CVI, in 16 age-matched normal controls, and in 53, healthy 5-7 month-old infants. The carrier consisted of a 1 c/deg vertical sinusoidal grating shown at 3.75Hz on/off presentation at a space-average luminance of 109 cd/m2. For children with CVI, and for age-matched control children, contrast was increased from 10% to 80% in 10-logarithmic steps during each 10-second trial, and multiple trials were signal-averaged. In healthy 5-7 month-old infants, contrast was swept from 0.5 to 20%. Response amplitudes were measured and thresholds were estimated by extrapolation of the VEP response function to zero amplitude. Threshold comparisons were made with healthy, full term, 5-7 month-old infants. Signal amplitude comparisons were made with age-matched control children.
30 of 34 children with CVI had measurable contrast thresholds ranging from 5% to 30%. The median threshold for these 30 children with CVI was 10.6%, approximately 8 times worse than 1.3% median threshold for 5-7 month-old healthy infants in this study. Compared with age-matched control children, children with CVI showed significant suprathreshold response losses; i.e., diminished signal amplitudes in the visible sweep range.
Contrast sensitivity and VEP response amplitudes are strongly affected by cortical visual impairment (CVI). This finding is important for health care providers, since it demonstrates that children with CVI should be taught and placed in high-contrast environments.
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