Eye Tracking-Based Characterization of Fixations during Reading in Children with Neurodevelopmental Disorders.

An efficient mode of evaluation for eye movements is the use of objective eye tracking systems combined with subjective tests (NSUCO or DEM), which are easily applicable across all age groups and in eye care clinical settings. The objective of this study was to characterize fixations during reading in two groups: a group of children with neurodevelopmental disorders (NDDG, 24 children, age: 6-12 years) and a group of children with oculomotor anomalies but without NDD (OAG, 24 children, age: 6-12 years). The results obtained were compared with those from a control group (CG, 20 children, age: 6-12 years). Specifically, the outcomes obtained with two subjective score systems, the Northeastern State University College of Optometry's Oculomotor (NSUCO) test and the Developmental Eye Movement (DEM) test, were compared with the objective analysis obtained through a commercially available eye tracker (Tobii Eye X, Tobii, Stockholm, Sweden). Specialized analysis software, namely Clinical Eye Tracker 2020 (Thomson Software Solutions, Welham Green, UK), was used. It was found that children with NDD had impaired oculomotor skills. A higher number of regressions, more fixations, and longer durations of fixations appear to be characteristic signs of this population group. Additionally, children with NDD took longer to complete the DEM test, as well as exhibiting more errors. The use of objective videoculographic systems for eye tracking and subjective tests like the NSUCO or DEM are good tools to assess saccadic movements, allowing the detection of oculomotor abnormalities in children with NDD.

Objective and Subjective Evaluation of Saccadic Eye Movements in Healthy Children and Children with Neurodevelopmental Disorders: A Pilot Study.

The objective of this study was to characterize saccades in children with neurodevelopmental disorders (NDDG, 17 children, age: 7-12 years) and compare them with a control group (CG, 15 children, age: 7-12 years), comparing the outcomes obtained with a subjective score system (Northeastern State University College of Optometry's Oculomotor test, NSUCO) with the objective analysis obtained through a commercially available Eye Tracker (Tobii Eye X, Tobii, Stockholm, Sweden) and a specialized software analysis (Thomson Software Solutions, Welham Green, UK). Children from the NDDG obtained significantly lower NSUCO scores (p < 0.001) compared with CG. Concerning eye tracking analyses, we found a significantly higher number of hypometric saccades in NDGG (p ≤ 0.044). Likewise, we found a significantly higher percentage of regressions in the NDDG for a time interval of presentation of stimuli of 1 s (p = 0.012). Significant correlations were found between different NSUCO scores and percentage of regressions, number of saccades completed and number of hypometric saccades. The presence of hypometric saccades and regressions seems to be a differential characteristic sign of children with neurodevelopmental disorders that can be detected using an objective eye tracking analysis, but also using the subjective test NSUCO that can be easily implemented in all clinical settings.

Distribution of Visual and Oculomotor Alterations in a Clinical Population of Children with and without Neurodevelopmental Disorders.

A prospective, non-randomized comparative study was conducted to compare the distribution of oculomotor and visual alterations in children with neurodevelopmental disorders and healthy children without such disorders. Sixty-nine children (aged 6-13 years) were enrolled and divided into three groups: a control group (CG) of 23 healthy children; a group of 18 healthy children with oculomotor abnormalities (OAG); and a group of 28 children with a neurodevelopmental disorder (NDDG), with 15 cases of dyslexia, 7 cases of developmental coordination disorder (DCD) and 6 cases of attention deficit/hyperactivity disorder (ADHD). Significantly worse near stereopsis was found in NDDG compared with CG (p < 0.001) and OAG (p = 0.001). Likewise, a significantly lower amplitude of accommodation was found in NDDG compared with CG in both the right (p = 0.001) and left eyes (p < 0.001). No statistically significant differences between groups were found in the measurement of near and distance phoria (p ≥ 0.557), near point of convergence (p = 0.700) and fusional vergences (p ≥ 0.059). Significantly impaired oculomotor test scores were found in NDDG compared with CG (p < 0.001), with no significant differences between OAG and NDDG (p ≥ 0.063). The comparison between the three types of neurodevelopmental disorders included revealed the presence of a significantly lower amplitude of accommodation in children with DCD compared with dyslexics. Furthermore, less exophoria at near was present in children with dyslexia compared with children with ADHD (p = 0.018) and DCD (p = 0.054). In conclusion, children with dyslexia, ADHD and DCD show an altered oculomotor pattern and a more reduced amplitude of accommodation, not always compatible with the diagnostic criteria of an accommodative insufficiency. Accommodative and binocular vision problems are not always present in these children and cannot be considered an etiologic factor.

Clinical Characterization of Oculomotricity in Children with and without Specific Learning Disorders.

Children with specific learning disorders have been associated with oculomotor problems, with their analysis even suggested to be a potential diagnostic tool. A prospective non-randomized comparative study evaluating 59 children (6-13 years old) divided into three groups was conducted: a control group (CG) including 15 healthy emmetropic children; a group of 18 healthy children with oculomotor abnormalities (OAG); and a group of 26 children diagnosed with specific learning disorders (LDG). In all groups, besides a complete eye exam, oculomotricity was characterized with two clinical tests: Northeastern State University College of Optometry's Oculomotor (NSUCO) and Developmental Eye Movement (DEM) tests. Concerning the NSUCO test, lower ability, precision, and head/body movement associated scorings were obtained for both smooth pursuits and saccades in OAG and LDG when compared to the CG (p < 0.001). Likewise, significantly longer time needed to read the horizontal sheet of the DEM test and a higher DEM ratio were found in OAG and LDG compared to CG (p ≤ 0.003). No differences between LDG and OAG were found in the performance with the two oculomotor tests (p ≥ 0.141). Oculomotor anomalies can be present in children with and without specific learning disorders, and therefore cannot be used as diagnostic criteria of these type of disorders.

Diagnosis of oculomotor anomalies in children with learning disorders.

This systematic review presents the existing scientific evidence for oculomotor anomalies in children with three different types of learning disorders - namely, dyslexia, dyspraxia and attention deficit-hyperactivity disorder (ADHD). This review was registered in the PROSPERO database (registration number: 139317). The QUADAS-2 tool was used to systematically evaluate the quality of the diagnostic tests used in the evaluated studies and to confirm whether the oculomotor alterations observed in the different groups of children with various learning disorders had a consistent diagnostic basis. Using this tool, the design of the articles was well elaborated, although concerns exist regarding the selection of patients and the diagnostic criteria for the binocular conditions. All the studies reviewed conclude that a pattern of oculomotor anomalies exist in the groups of children with these three types of learning disorders compared to healthy children. However, there is a concern regarding the diagnostic methodology, as no clear range of normality for the parameters used to characterise ocular motility was identified and no gold standard or reference test has been defined. In future studies, this range of normality must be developed for different oculomotor skills, and a reference test (possibly video-oculography) for the measurement of these skills must be established.