Boot, F.H.

Visual processing dysfunctions in children with intellectual disabilities (Doctoral Thesis)

2013-01-23T00:00:00Z

Bij kinderen met een verstandelijke beperking verwacht je een verhoogd risico op visuele verwerkingsproblemen door hun hersenschade of hersenontwikkelingsstoornis. Hierbij hoeft er op oogheelkundig niveau geen pathologie aanwezig te zijn, wat in de huidige kliniek cerebrale visuele inperking (CVI) wordt genoemd. CVI kan tot uiting komen in stoornissen van de visuele functies die leiden tot perceptie, de zogenoemde hogere visuele functies. Voorbeelden van hogere visuele functies zijn het detecteren van beweging, het herkennen van vormen en ruimtelijke oriëntatie. Huidige diagnostiek van hogere visuele dysfuncties, en dus CVI, vindt plaats door middel van neuropsychologische testmethodes. Het nadeel van deze testmethodes is dat zij alleen inzetbaar zijn bij kinderen met een ontwikkelingsleeftijd >4 jaar. Dit betekent dat hogere visuele functies bij kinderen met een verstandelijke beperking, maar ook bij gezonde kinderen <4 jaar met een typische ontwikkeling, tot op heden niet of moeilijk getest kunnen worden. Het gevolg is dat de prevalentie van CVI in deze groepen waarschijnlijk onderschat wordt en dat kinderen mogelijk niet de juiste visuele ondersteuning en stimulatie krijgen. In de huidige praktijk is het bestuderen van oogbewegingen en kijkgedrag een directe manier om visuele verwerking en oogmotoriek te beoordelen. Een vertraagde visuele verwerking wordt als een verhoogd risico op CVI gezien en het beoordelen van oogbewegingen kan dus worden gebruikt als een screeningsmethode voor CVI. Het nadeel is echter dat dit is gebaseerd op observaties zonder kwantitatieve uitkomstmaat. Voor dit proefschrift wordt er daarom voor het eerst gebruik gemaakt van een geautomatiseerde methode, waarbij oogbewegingen objectief worden gemeten. Op een tv scherm worden visuele stimuli gepresenteerd, terwijl infrarood camera’s de oogbewegingen detecteren. Instructies en feedback van de deelnemer zijn niet nodig, waardoor ook kinderen met een verstandelijke beperking kunnen worden onderzocht. Op basis van oogbewegingreacties kan er onderscheid worden gemaakt tussen normale visuele verwerking, vertraagde visuele verwerking en stoornissen in de oogmotoriek. De resultaten van deze studie laten zien dat er een verhoogd risico bestaat van visuele verwerkingsproblematiek bij kinderen met een verstandelijke beperking, waarvan de ernst toeneemt met de mate van de verstandelijke beperking. Daarbij bestaat er een verscheidenheid aan visuele dysfuncties binnen deze groep. Kinderen met een ontwikkelingsstoornis en/of verstandelijke beperking zouden op jonge leeftijd al moeten worden gescreend en zo nodig naar onderzoekcentra voor slechtzienden worden verwezen voor verder onderzoek.

Factors related to impaired visual orienting behavior in children with intellectual disabilities (Article)

2012-05-07T00:00:00Z

It is generally assumed that children with intellectual disabilities (ID) have an increased risk of impaired visual information processing due to brain damage or brain development disorder. So far little evidence has been presented to support this assumption. Abnormal visual orienting behavior is a sensitive tool to evaluate impaired visual information processing. Therefore, the main objective of this study was to investigate possible correlations between the children's characteristics (age, gender, level of ID, mobility, gestational age, cerebral palsy, Down syndrome, visual acuity, strabismus, nystagmus, and epilepsy), and abnormal visual orienting behavior. We quantified data on visual orienting behavior, in terms of visual processing time and ocular motor fixations, in 88 children with ID aged 4-14 years. These visual parameters were combined with data collected from the children's medical records (predictors) and were put in a Pearson bivariate correlation analysis. A predictor was included for multiple regression analysis if the Pearson's correlation coefficient had a level of significance of p<0.05. As shown by multiple regression analysis, age, level of ID, and Down syndrome significantly affected visual processing time. Mobility, strabismus, and nystagmus significantly affected fixation quality.Using a systematic approach, we confirmed the hypothesis that children with ID have an increased risk of impaired visual information processing which is related to a low IQ.

Quantification of visual orienting responses to coherent form and motion in typically developing children aged 0-12 years (Article)

2012-05-01T00:00:00Z

PURPOSE. Brain damage or brain development disorders can affect (the maturation of) visual processing functions, such as form and motion detection. The aim of our study was to investigate visual orienting responses of children to a coherent form and motion stimulus as a measure for maturation of visual information processing. METHODS. The 213 typically developing children aged 0-12 years included in this study were shown a 100% coherent form and motion expansion stimulus on a remote eye tracking monitor. Orienting eye movements were quantified in terms of ocular motor reaction time to fixation (RTF). Children were divided in age groups, and their performance was compared to 30 healthy adults with a mean age of 24.49 years (SD 3.62 years). RESULTS. The RTF values of coherent form in children up to six years old were significantly higher compared to the adult group (P < 0.05, Dunnett post-hoc test). For motion, mature levels were reached at eight years old. RTF values depended on stimulus type (F1,168= 240.8, P < 0.001) and age (F11,168= 25.8, P < 0.001), and there was a significant age by stimulus type interaction (F11,168 = 2.2, P < 0.05). CONCLUSIONS. Remote eye tracking may provide objective insight into the maturation of visual information processing of coherent form and motion without complex instructions or active cooperation. The quantification of typical visual orienting behavior in childhood may be used as a reference for children with brain dysfunction.

Effects of visual processing and congenital nystagmus on visually guided ocular motor behaviour (Article)

2011-04-01T00:00:00Z

Aim: The aim of this study was to compare visually guided ocular motor behaviour in children with visual processing and/or motor deficits with an age-matched comparison group and an adult group. Method: Visual stimuli were shown to 28 children with visual processing and/or motor deficits (11 females, 17 males; mean age 7y 5mo, SD 2y 9mo, range 2-14y;) and an age-matched comparison group of 213 typically developing children (115 females, 98 males; mean age 5y 8mo, SD 3y 5mo, range 0-12y). The adult group consisted of nine females and two males with (mean age of 24y 4mo, SD 4y 8mo). Individuals who had a likely diagnosis of cerebral visual impairment (CVI), an opticopathy with unknown location, nystagmus, glaucoma, or a cataract were included in the study. Exclusion criteria were a visual acuity below 0.2, a developmental age under 1year, and the presence of brain tumours, autism, and anxiety disorders. Orientating eye movements to large cartoons were quantified using the reaction time to fixation (RTF) and gaze fixation area (GFA). A Mann-Whitney U test was used to compare the differences between groups and Bonferroni post-hoc testing was used to analyse age dependence of RTF and GFA values within the comparison group. Results: Individuals with CVI showed significantly prolonged RTF values; those with congenital nystagmus showed significantly increased GFA values. In the comparison group, RTF was significantly longer in children under the age of 2years than in children aged 4years and older (290 and 200ms respectively; p<0.001). No developmental change was found for GFA values. Interpretation: Increased RTF values in individuals with CVI relate to visual processing deficits. The data suggest that visually guided ocular motor responses mature during the first 3years of life. © The Authors. Journal compilation

Cerebral Visual Impairment: Which perceptive visual dysfunctions can be expected in children with brain damage? A systematic review (Article)

2010-11-01T00:00:00Z

The current definition of Cerebral Visual Impairment (CVI) includes all visual dysfunctions caused by damage to, or malfunctioning of, the retrochiasmatic visual pathways in the absence of damage to the anterior visual pathways or any major ocular disease. CVI is diagnosed by exclusion and the existence of many different causes and symptoms make it an overall non-categorized group. To date, no discrimination is made within CVI based on types of perceptive visual dysfunctions. The aim of this review was to outline which perceptive visual dysfunctions are to be expected based on a number of etiologies of brain damage and brain development disorders with their onset in the pre-, peri- or postnatal period. For each period two etiologies were chosen as the main characteristic brain damage. For each etiology a main search was performed. The selection of the articles was based on the following criteria: age, etiology, imaging, central pathology and perceptive visual function test. The perceptive visual functions included for this review were object recognition, face recognition, visual memory, orientation, visual spatial perception, motion perception and simultaneous perception. Our search resulted in 11 key articles. A diversity of research history is performed for the selected etiologies and their relation to perceptive visual dysfunctions. Periventricular Leukomalacia (PVL) was most studied, whereas the main tested perceptive visual function was visual spatial perception. As a conclusion, the present status of research in the field of CVI does not allow to correlate between etiology, location and perceptive visual dysfunctions in children with brain damage or a brain development disorder. A limiting factor could be the small number of objective tests performed in children experiencing problems in visual processing. Based on recent insights in central visual information processing, we recommend an alternative approach for the definition of CVI that is based on functional visual processing, rather than anatomical landmarks. This could be of benefit in daily practice to diagnose CVI.