The childhood condition of visual difficulties caused by brain damage, commonly termed cortical or cerebral visual impairment (CVI), is well established but has no internationally accepted definition. Clarification of its core features is required to advance research and clinical practice. This systematic review aimed to identify the definitions of childhood CVI in the original scientific literature to describe and critically appraise a consensual definition of the condition. MEDLINE, EMBASE, PsychINFO, CINAHL and AMED databases were searched in January 2017. Studies were included if they (1) were published original research, (2) contained a childhood CVI sample, (3) contained a definition of CVI and (4) described their CVI identification/diagnostic method. Thematic analysis identified concepts within definitions and narrative synthesis was conducted. Of 1150 articles, 51 met inclusion criteria. Definitions were subdivided according to detail (descriptive definition, description not reaching definition status and diagnostic/operationalising criteria). Three themes concerning visual deficits, eye health and brain integrity were identified (each containing subthemes) and analysed individually across definitions. The most common themes were ‘visual impairment’ (n=20), ‘retrochiasmatic pathway damage’(n=13) and ‘normal/near normal eye health’ (n=15). The most consensual definition identified here may not be the best quality for advancing our understanding of CVI. We argue for the alternative definition: CVI is a verifiable visual dysfunction which cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment. We propose reporting guidelines to permit comparison across studies and increase the evidence base for more reliable clinical assessment and diagnosis.

Background: To quantify development of gaze stability throughout life during short and long fixational tasks using eye tracking technology. Methods: Two hundred and fifty-nine participants aged between 5 months and 77 years were recruited along the study. All participants underwent a complete ophthalmological assessment. Fixational behavior during long and short fixational tasks was analyzed using a DIVE (Device for an Integral Visual Examination), a digital test assisted with eye tracking technology. The participants were divided into ten groups according to their age. Group 1, 0–2 years; group 2, 2–5 years; group 3, 5–10 years; group 4, 10–20 years; group 5, 20–30 years; group 6, 30–40 years; group 7, 40–50 years; group 8, 50–60 years; group 9, 60–70 years; and group 10, over 70 years. Results: Gaze stability, assessed by logBCEA (log-transformed bivariate contour ellipse area), improved with age from 5 months to 30 years (1.27 vs. 0.57 deg² for long fixational task, 0.73 vs. −0.04 deg² for short fixational task), while fixations tend to be longer (1.95 vs. 2.80 msec for long fixational tasks and 0.80 vs. 1.71 msec for short fixational tasks). All fixational outcomes worsened progressively from the fifth decade of life. Log-transformed bivariate contour ellipse area (0.79, 0.83, 0.91, 1.42 deg² for long fixational task and 0.01, 0.18, 0.28, 0.44 deg² for short fixational task, for group 7, 8, 9, and 10 respectively). Stimuli features may influence oculomotor performance, with smaller stimuli providing prolonged fixations. Conclusions: Fixational behavior can be accurately assessed from 5 months of age using a DIVE. We report normative data of gaze stability and duration of fixations for every age group. Currently available technology may increase the accuracy of our visual assessments at any age.

Although steady fixation is a key aspect of a proper visual function, it is only subjectively assessed in young and uncooperative children. In the present study, we characterize the development of fixational behavior throughout childhood in a large group of healthy children 5 months of age and up, recruited in five geographically diverse sites. In order to do it, we examined 802 healthy children from April 2019 to February 2020. Their oculomotor behavior was analyzed by means of an automated digital system, based on eye-tracking technology. Oculomotor outcomes were gaze stability, fixation stability and duration of fixations (for both long and short fixational tasks), and saccadic reaction time. Ninety-nine percent of all recruited children were successfully examined. Fixational and saccadic performance improved with age throughout childhood, with more pronounced changes during the first 2 years of life. Gaze and fixation tended to be more stable with age (p < 0.001 for most the outcomes), and saccades tended to be faster. In a multivariate analysis, including age and ethnicity as independent variables and adjusting by data quality, age was related with most fixational outcomes. Our automated digital system and eye-tracking data allow us to quantitatively describe the development of oculomotor control during childhood, assess visual fixation and saccadic performance in children 5 months of age and up, and provide a normative reference of fixational outcomes for clinical practice.