Abnormalities in Distribution and Transformation of Visual Iinputs in Children with CVI

摘要

Purpose: Cerebral visual impairment (CVI) is a common visual disorder in children. In this study we report 10 children with subnormal or absent visual orienting behaviors in whom cortical activation was demonstrated by VEP and reflexive eye movements were present. Methods Testing included assessment of visual acuity Teller Acuity Cards or Snellen optotype), transient visual evoked potentials (VEPs) to check reversal and pattern-onset stimuli, eye movement recordings (EOG or IR video-oculography) and neuroimaging studies (CT or MRI). Results: All of the children had abnormal visual behaviors ranging from complete lack of visually guided eye movements to reading disability. Visual acuities ranged from 20/20 to 20/2700. In general, reflexive eye movements were present (VOR and OKN) whereas visually guided eye movements (smooth pursuit and saccade gains) were variably reduced. The eye examinations were otherwise normal. Neurodevelopment was uniformly delayed. Neuroimaging revealed delayed myelination or dysmyelination in 8 children; the remaining 2 children had hydrocephalus or diffuse polymicrogyria sparing the occipital cortex. Transient VEPs were normal or mildly abnormal in terms of amplitude, latency and waveform. Conclusion: We report 10 subjects with normal or mildly abnormal visual cortical activation and the presence of VOR and OKN who demonstrate variable deficits or absence of visually guided eye movements. These findings are consistent with abnormalities in the distribution and transformation of visual inputs into accurate smooth pursuit and targeted saccades.