Observations of gaze dysfunction in CP have been described using a variety of terms: uncoordinated saccades and pursuit
53 ; paroxysmal ocular deviations
53 ; stability of fixation inability
53 ; struggling with fixation and eye movement
67 ; complete disruption of ocular motor organization
52 ; dyskinetic eye movement disorder
67 ; and ocular motor apraxia.
52 Jan et al.
67 reported that one or more of these deficits was present in all 14 children chosen for study because of severe, dyskinetic CP. Salati et al.
53 stated a prevalence ≥78% in children chosen for study using the broader definition of CVI, 77% of whom were categorized as having spastic or mixed, moderate-to-severe quadriplegia.
The results of our study indicate lower prevalences of gaze dysfunction: an average 22% in children with quadriplegic CP; an average 18% in children of CP levels 3 to 5; and an average 8% for levels 1 to 2. Irrespective of discrepancies in prevalence, conjugate gaze deficits deserve better recognition as significant components of visual impairment in children with CP, as they often masquerade as CVI. We were struck by the number of children in our cohort who had normal or mildly subnormal visual acuity, but who, on review of outside medical records, had been labeled as having “cortical blindness.” Parents, therapists, and other healthcare professionals described them variously as: “visually inattentive,” “unable to see or follow,” “no eye contact,” “looks away,” “looks over,” or “uses only peripheral vision.” Careful clinical observation and eye movement recordings revealed combined saccadic and smooth pursuit gaze apraxia/palsy, and fixation impersistence. The children with these deficits who retained head and neck control used horizontal or vertical head thrusts to facilitate gaze shifts. Restraining head motion tended to exacerbate the impairments by prolonging latencies, reducing saccade amplitudes, and reducing pursuit/OKN velocity matching. The deficits impaired both horizontal and vertical gaze, but were often more pronounced for vertical target steps and target motion.