Abstract
Purpose: :
The aim of the present study was to determine the visual acuity in children with Cerebral Palsy (CP) and relate it to the degree of motor impairment in children with all subtypes of CP.
Methods: :
Visual acuity was determined using Snellen's charts, Spatial sweep Visual Evoked Potential (VEP) and Flash VEP. Motor impairment was rated according to the Gross Motor Function Classification System (GMFCS) in five levels of severity.
Results: :
Visual acuity using Snellen's chart was difficult to determine in patients with severe CP (GMFCS 4–5) compared to those with less severe CP (GMFCS 1–3)– p value: 0.0104 Fischer exact two tailed test. Thus, monocular visual acuity was determined using spatial sweep VEP in 22 patients aged from 1 year– 15 years. A one–way ANVOA was performed to look for significant differences in visual acuity between the five GMFCS levels and linear regression was also done to look for a correlation between visual acuity loss and the GMFCS ratings. Differences between the five levels of GMFCS rating were not statistically significant (p value: 0.9746). Also, Flash VEP was used to investigate for anterior visual pathway disease particularly in patients whose spatial sweep VEP was inconclusive or not obtainable. The amplitude and latencies of Flash VEP were studied as a function of GMFCS ratings and linear regression was performed.
Conclusions: :
It is difficult to estimate visual acuity using standard clinical methods in children with CP particularly those with severe motor impairment. However, on spatial sweep VEP and Flash VEP no correlation between visual acuity loss and severity of motor impairment was found. Thus, we conclude that many children with severe cerebral palsy are misdiagnosed as having low visual acuity based on standard clinical exam. Thus, treatment for strabismus, nystagmus should not be deferred in children with CP without using specialized electrodiagnostic techniques to determine the visual acuities.
Keywords: electrophysiology: clinical • visual acuity • neuro-ophthalmology: cortical function/rehabilitation