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T.A. Watson, D. Orel–Bixler, G. Haegerstrom–Portnoy; VEP Acuity Predicts Future Behavioral Acuity in Children With Cortical Visual Impairment . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3477.
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© ARVO (1962-2015); The Authors (2016-present)
Cortical visual impairment (CVI) is bilateral visual impairment caused by damage to the posterior visual pathway, the visual cortex or both. CVI is the leading cause of bilateral vision impairment in children in the Western world. The prognosis in CVI is variable with some children recovering significant vision function over time and others remaining stable. The purpose of this study was to determine if a visual evoked potential (VEP) measure of visual acuity is predictive of the future acuity of the child measured behaviorally.
The visual acuity of 28 children with CVI was assessed using the sweep VEP and a behavioral measure on two occasions. 16 of the 28 children were tested with UCB preferential grating cards and 12 were tested with single symbols. At the time of the first test, the children ranged in age from 1.25 to 11.1 years (mean: 5.4 years). The time between measures ranged from 0.9 to 13.2 years (mean: 6.6 years). Improvement in vision function was defined as a 0.2 log MAR improvement of behavioral visual acuity.
Significant improvement in behavioral visual acuity was found in 23 of 28 children. The average improvement for the whole group was 0.46 log unit (from Snellen equivalent of 20/350 to 20/120). The average improvement for those that met the criterion of 0.2 log MAR improvement in visual acuity was 0.62 log unit (from Snellen equivalent of 20/445 to 20/107). At the initial test, the behavioral measures were significantly worse than the VEP measures of acuity (mean of 20/350 vs. 20/113; p<0.0001). The initial VEP measure was not statistically different from the later behavioral measure (p=0.4). The average difference between the initial VEP acuity and the later behavioral acuity for all 28 children was only –0.03 log unit (mean change from 20/113 to 20/120) and was only 0.04 log unit for those 23 that improved (from 20/117 to 20/107). Therefore, the initial VEP acuity was predictive of the later behavioral visual acuity.
82% of children with CVI showed significant improvement of visual acuity over time measured behaviorally. Even though the initial VEP measure of acuity was much better than the initial behavioral measure, the initial VEP measure was numerically predictive of the behavioral acuity measured on average 6.6 years later.
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