Assessment of Gaze Fixations and Shifts in Children with Cerebral Palsy: A Comparison of Computer- and Object-Based Approaches

Background/Objectives: Gaze behaviours, such as fixation on single objects, and switching gaze between two objects are important for signaling messages, making choices or controlling a computer for children with cerebral palsy (CP) and similar movement disabilities. Observing these behaviours can be challenging for clinicians, with a lack of agreement on how they can be objectively quantified or rated. Methods: This study compares two methods of eliciting and observing gaze behaviours: a computer presentation using an eye tracker and an object presentation scored by two independent observers in order to explore the utility of each to clinicians working in this area. Children with CP (n = 39) attempted single-target fixation (STF) and target-target fixation shift (TTFS) tasks using both presentations and the results were compared. Results: Six children were unable to calibrate the eye tracker to the accuracy level required. Significantly higher scores for both STF (81.3% object presentation and 30.3% computer presentation, p < 0.01) and TTFS (70.1% and 26.9%, p < 0.01) were seen on the object presentation, with children's performance not predicted by developmental age, severity of CP or presence or absence of strabismus. It is not possible to definitively state which method gives the "correct" result; however, the difference in reported success rate merits further discussion. Conclusions: Whilst eye tracking may present an "entry barrier" for some children in terms of its accuracy and calibration requirements, object presentation carries with it the risk of over-interpreting children as having fixated. Conversely, eye tracking may be better at recording fixations in children with strabismus, where object-based paradigms may offer more flexible administration for clinicians. The variability in children's performance on both presentations underlines the risk of assuming these skills to be present and the importance of assessing gaze behaviours in individual children.