Why CVI stands out as the most impaired group
In a direct comparison of school-age children, those with CVI had more impaired search performance than children with ADHD, dyslexia, or typical development, even when their basic visual acuity was normal [1]. The difficulty was greatest in crowded and unstructured displays—scenes with many competing objects and no clear organizing pattern [1]. This fits the idea that the problem is not in seeing the target but in selecting it from everything else.
Gaze-based measurements showed what that looks like in practice: children with CVI searched over larger areas and needed more time to recognize a target, particularly after their eyes had already landed on it [1]. In other words, the eyes arrived but the recognition did not follow promptly. The authors interpret this tendency to overlook a target while fixating on it as pointing toward higher-order visual function deficits—problems with interpreting and selecting what is seen, rather than with the eyes themselves [1].
How ADHD and dyslexia differ from CVI and from each other
A scoping review of 35 studies covering children aged 6–12 found that all three clinical groups show some degree of impaired visual search compared with typically developing children, but the profile of impairment is not the same [2]. In ADHD, the characteristic pattern is poor accuracy rather than slow reaction time—children make more mistakes without necessarily taking longer [2]. In dyslexia, children tend to be both slower and less accurate, with the exact pattern depending on the type of stimulus used [2].
The review also notes that mechanisms beyond visual selective attention may shape these patterns: a speed–accuracy trade-off or an executive functioning deficit in ADHD, and a phonological deficit in dyslexia, could influence how children approach a search task [2]. These are proposed explanations rather than settled causes, and the review itself describes the data on ADHD and dyslexia as technically inconclusive for clean clinical discrimination [2].
The same search difficulty appears in preschoolers and has a neural signature
Visual search problems in CVI are not limited to school-age children. In a paper–pencil cancellation task, preschoolers aged 3–5 with CVI were less accurate, took longer, left larger gaps between targets, and revisited clusters of targets more often than both neurotypical children and children only at risk of CVI [4]. That study used a modified approach to extract search efficiency from the path a child took through the page, and it concluded that first signs of both global and local visual selective attention deficits can be detected this early [4].
A separate study using a virtual-reality search task with EEG recordings found that individuals with CVI had lower success rates, longer reaction times, larger search areas, and more gaze error than neurotypical controls [5]. The CVI group also lacked a strong, well-defined drop in posterior alpha-band brain activity after a stimulus appeared—a signal involved in coordinating visual processing—and the size of that missing drop was associated with worse search performance and with smaller volume of specific visual thalamic nuclei [5]. This suggests that search difficulties in CVI are linked to altered brain rhythms and early neurological injury, though the study did not include children with ADHD or dyslexia, so it cannot speak to how those groups differ neurally [5].
Can search performance actually distinguish these children in the clinic?
The practical goal behind this research is differential diagnosis, and the evidence so far is promising but not yet clean. The direct comparison study describes its gaze-based method as feasible, valid, and promising for distinguishing CVI from ADHD and dyslexia [1]. The scoping review is more cautious, noting sparse data on children with an official CVI diagnosis and technically inconclusive data on ADHD and dyslexia, which together make it complex to discriminate between these populations in clinical practice based on visual search alone [2].
Parent-reported visual problems show a similar overlap. Parents report more visual problems in children with CVI than in all other groups, unaffected by visual acuity, but they also report more visual problems in children with ADHD or dyslexia than in neurotypical children on most higher-order visual function categories [3]. Children with ADHD had significantly more parent-reported behavioral problems, yet parents of children with CVI also reported more behavioral problems than parents of neurotypical children [3]. Because of this overlap, the authors propose a shortened screening list to improve differentiation between CVI and ADHD or dyslexia based on everyday visual problems [3]. The takeaway is that search tasks and eye tracking add useful information, but no single measure yet separates these groups on its own.
Sources used in this answer
Eyes on CVI: Eye movements unveil distinct visual search patterns in Cerebral Visual Impairment compared to ADHD, dyslexia, and neurotypical children
Children with CVI had more impaired visual search than children with ADHD, dyslexia, or typical development, especially in crowded and unstructured displays, and gaze analysis showed they searched larger areas and needed more time to recognize a target after first fixating on it.
Visual selective attention and visual search performance in children with CVI, ADHD, and Dyslexia: a scoping review
A scoping review of 35 studies found all three groups have some visual search impairment compared with typical children, with CVI tending toward slower and less accurate responses, ADHD toward poor accuracy rather than reaction time, and dyslexia toward slower and less accurate responses depending on stimulus type.
Parent-reported problems in children with Cerebral Visual Impairment: Improving the discriminative ability from ADHD and dyslexia using screening inventories
Parents reported more visual problems in children with CVI than in all other groups regardless of visual acuity, but also more visual problems in children with ADHD or dyslexia than in neurotypical children on most higher-order visual function categories, complicating screening differentiation.
Exploring visual search performance in preschool children with Cerebral Visual Impairment: A modified approach
Preschoolers aged 3–5 with CVI showed lower accuracy, longer completion times, greater inter-target distances, and more cluster revisits on a paper–pencil search task than both CVI-risk and neurotypical children.
Visual search performance in cerebral visual impairment is associated with altered alpha band oscillations
Individuals with CVI showed impaired visual search in a virtual-reality task along with a lack of strong posterior alpha desynchronization, and the magnitude of that alpha deficit was associated with worse search performance and smaller volume of specific visual thalamic nuclei.