Dyslexia is a neurodevelopmental reading disability estimated to affect 5–10% of the population. While there is yet no full understanding of the cause of dyslexia, or agreement on its precise definition, it is certain that many individuals suffer persistent problems in learning to read for no apparent reason. Although it is generally agreed that early intervention is the best form of support for children with dyslexia, there is still a lack of efficient and objective means to help identify those at risk during the early years of school. Here we show that it is possible to identify 9–10 year old individuals at risk of persistent reading difficulties by using eye tracking during reading to probe the processes that underlie reading ability. In contrast to current screening methods, which rely on oral or written tests, eye tracking does not depend on the subject to produce some overt verbal response and thus provides a natural means to objectively assess the reading process as it unfolds in real-time. Our study is based on a sample of 97 high-risk subjects with early identified word decoding difficulties and a control group of 88 low-risk subjects. These subjects were selected from a larger population of 2165 school children attending second grade. Using predictive modeling and statistical resampling techniques, we develop classification models from eye tracking records less than one minute in duration and show that the models are able to differentiate high-risk subjects from low-risk subjects with high accuracy. Although dyslexia is fundamentally a language-based learning disability, our results suggest that eye movements in reading can be highly predictive of individual reading ability and that eye tracking can be an efficient means to identify children at risk of long-term reading difficulties.

Background:It is well known that problems with binocular vision can cause issues for reading; less known is to what extent binocular vision improves reading performance. The purpose of this study was to explore the role of binocularity by directly comparing monocular and binocular reading in subjects with typical reading skills and normal binocular vision. A secondary purpose was to assess any asymmetry in monocular performance and its association with the sighting dominant eye. Methods: In a balanced repeated measures experiment, 18 subjects read paragraphs of text under monocular and binocular conditions. All subjects went through an optometric examination before inclusion. Reading speed and eye movements were recorded with an eye tracker. Results: The mean difference in reading speed (2.1 per cent) between monocular (dominant and non-dominant eye averaged) and binocular reading speed was not significant. A significant difference in reading speed was found between binocular and the non-dominant eye, as determined by the far sighting test (p = 0.03). Monocular reading showed significantly increased (8.9 per cent) fixation duration (p < 0.01) and longer regressive saccades by 0.43 character spaces (p < 0.01). Reading with the non-dominant eye, as determined by the near sighting test, showed increased progressive saccade length by 0.2 characters compared to the dominant eye (p = 0.03). No other significant differences between dominant and non-dominant eyes were found. The agreement between the faster reading eye and ocular dominance was 44 to 56 per cent depending on whether dominance was determined at near or far. Conclusion:The outcomes suggest that in subjects with normal binocular vision, there is no marked enhancement in reading performance by binocular vision when reading paragraphs of text. Furthermore, the monocular reading performance appears to be close to equal and any small differences in performance appear not to be strongly associated with ocular dominance.

The binocular advantage in reading performance is typically small. On the other hand research shows binocular reading to be remarkably robust to degraded stimulus properties. We hypothesized that this robustness may stem from an increasing binocular contribution. The main objective was to compare monocular and binocular performance at different stimulus contrasts and assess the level of binocular superiority. A secondary objective was to assess any asymmetry in performance related to ocular dominance. In a balanced repeated measures experiment 18 subjects read texts at three levels of contrast monocularly and binocularly while their eye movements were recorded. The binocular advantage increased with reduced contrast producing a 7% slower monocular reading at 40% contrast, 9% slower at 20% contrast, and 21% slower at 10% contrast. A statistically significant interaction effect was found in fixation duration displaying a more adverse effect in the monocular condition at lowest contrast. No significant effects of ocular dominance were observed. The outcome suggests that binocularity contributes increasingly to reading performance as stimulus contrast decreases. The strongest difference between monocular and binocular performance was due to fixation duration. The findings may pose a clinical point that it may be necessary to consider tests at different contrast levels when estimating reading performance.

Background: Visual and oculomotor problems are very common in Parkinson’s disease (PD) and by using eye-tracking such problems could be characterized in more detail. However, eye-tracking is not part of the routine clinical investigation of parkinsonism. Objective: To evaluate gaze stability and pupil size in stable light conditions, as well as eye movements during sustained fixation in a population of PD patients and healthy controls (HC). Methods: In total, 50 PD patients (66% males) with unilateral to mild-to-moderate disease (Hoehn & Yahr 1– 3, Schwab and England 70– 90% ) and 43 HC (37% males) were included in the study. Eye movements were recorded with Tobii Pro Spectrum, a screen-based eye tracker with a sampling rate of 1200 Hz. Logistic regression analysis was applied to investigate the strength of association of eye-movement measures with diagnosis. Results: Median pupil size (OR 0.811; 95% CI 0.666– 0.987; p = 0.037) and longest fixation period (OR 0.798; 95% CI 0.691-0.921; p = 0.002), were the eye-movement parameters that were independently associated with diagnosis, after adjustment for sex (OR 4.35; 95% CI 1.516– 12.483; p = 0.006) and visuospatial/executive score in Montreal Cognitive Assessment (OR 0.422; 95% CI 0.233– 0.764; p = 0.004). The area under the ROC curve was determined to 0.817; 95% (CI) 0.732– 0.901. Conclusion: Eye-tracking based measurements of gaze fixation and pupil reaction may be useful biomarkers of PD diagnosis. However, larger studies of eye-tracking parameters integrated into the screening of patients with suspected PD are necessary, to further investigate and confirm their diagnostic value.

Different degrees of eye dominance may need to be considered when comparing monocular and binocular performance or estimating binocular summation effects. The purpose of this study was to explore eye dominance under binocular viewing conditions and observe gradual differences in preference. Two binocular eye-dominance tests were evaluated and compared to the hole-in-the-card sighting test. The first experiment was based on a binocular sighting test. The second originated from the variable-angle mirror test, utilizing physiological diplopia to determine which eye dominates the binocular percept. The participants were 32 healthy subject with normal sight. For both experiments there were plausible effects of different degrees of eye dominance affecting how the subjects positioned or perceived the scene. The outcomes were supported by a statistically significant correlation with an interocular difference in sensitivity to degraded visibility. A statistically significant correlation was found between the hole-in-the-card test and the variable-angle mirror test (r = 0.527, p < 0.01). The experiments confirm the plausible occurrence of forms of eye dominance under binocular viewing conditions. The correlation with the hole-in-the-card test was weak to moderate, due to factors that appear to be related to testing and viewing conditions. Interocular differences in sensitivity to blur appear to be a useful factor in further grading of eye dominance.