Visuele ontwikkeling. Refractive errors. Van het netvlies naar de hersenschors. Visueel systeem: prenatale ontwikkeling

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1 Visuele ontwikkeling Van het netvlies naar de hersenschors STAAFJES: perifeer zicht zien in het duister KEGELTJES: Centrale visus Kleurzicht Rechtstreeks uit het hersenweefsel Prosencefalon - optische blaasjes Optische zenuw later dan het oog Myelinisatie start bij chiasma opticum Visueel systeem: prenatale ontwikkeling Refractive errors The average refractive error in children from birth to 1 year of age is about 2 diopters (D) of hyperopia. Astigmatism up to 2 D is common in children under 3 years of age. Low amounts of anisometropia are common and variable in infants. 5

2 Retina Foveal region gets to be thinner ( 1000лm лm ) by 4 yrs. Cones density/area increases by age. More peripheral retina develops faster than foveal area. X,Y,W ganglion cells. Visual acuity the spatial resolving capacity of the visual system. Spatial resolution= angular resolution =describes the resolving power of the eye. Resolving poweris the ability of the components of an imaging device( e.g: eye) to measure the angular separationof the points in an object. Visual acuity Visual acuity is limited by diffraction, aberrations and photoreceptor density in the eye. a number of factors also affect visual acuity such as refractive error, illumination, contrast and the location of the retina being stimulated. Visual acuity Target detection requires only the perception of the presence or absence of an aspect of the stimuli. Landolt C and the Illiterate E are forms of detection used in visual acuity measurement in the clinic. Visual acuity 6/6 (20/20) Target recognition tasks

3 logmar logmar Vernier acuity Vernier acuity is the ability by a person to detect the proper alignment of two line segments Grating acuity aspect of visual acuity involving the ability to distinguish the elements of a fine grating composed of alternating dark and light stripes or squares. Angular acuity= Reading a letter Morphoscopic acuity=reading a letter in a line. Crowding phenomena=

4 Development of visual acuity Visual acuity contrast sensitivity Birth 6/300 unknown 3 months 6/ /60 6/60 1 yr 6/24 6/9 2 yrs 6/ /9 6/6 3 yrs 6/9 ---6/6 6/6 Saccadic system Smooth pursuit system Optokinetic nystagmus Visual milestones Babies are not born with all the visual abilities they need in life. The ability to focus their eyes, move them accurately, and use them together as a team must be learned. Eye and vision problems in infants can cause developmental delays. Not every child is the same and some may reach certain milestones at different ages. Birth-4 mo Up to about 3 months of age, babies' eyes do not focus on objects more than 2-3 meters from their faces. By eight weeks, babies begin to focus their eyes on the faces of a parent or other person near them. But they still cannot follow. For the first two months of life, an infant's eyes are not well coordinated, However, if an eye appears to turn in or out constantly, an evaluation is warranted. Babies should begin to follow moving objects with their eyes and reach for things at around four months of age. 5-8 months During these months, control of eye movements and eyebody coordination skills continue to improve. Depth perception is not present at birth. It is not until around the fifth month that the eyes are capable of working together to form a three-dimensional view of the world and begin to see in depth. it is generally believed that babies have good color vision by five months of age. Most babies start crawling at about 8 months old, which helps further develop eye-hand-foot-body coordination. Early walkers who did minimal crawling may not learn to use their eyes together as well as babies who crawl a lot.

5 9-12 months At around 9 months of age, babies begin to pull themselves up to a standing position. By 10 months of age, a baby should be able to grasp objects with thumb and forefinger. By twelve months of age, most babies will be crawling and trying to walk. Parents should encourage crawling rather than early walking to help the child develop better eye-hand coordination. Babies can now judge distances fairly well and throw things with precision months By two years of age, a child's eye-hand coordination and depth perception should be well developed. Children this age are highly interested in exploring their environment and in looking and listening. They recognize familiar objects and pictures in books and can scribble with pencil months At around 9 months of age, babies begin to pull themselves up to a standing position. By 10 months of age, a baby should be able to grasp objects with thumb and forefinger. By twelve months of age, most babies will be crawling and trying to walk. Parents should encourage crawling rather than early walking to help the child develop better eye-hand coordination. Twee visuele systemen ontwikkelen Primair/retinocorticaal visueel systeem Subcorticaal/retinotectaal visueel systeem Babies can now judge distances fairly well and throw things with precision. 28 The retinotectal system 29 30

6 12 32 Retinotectaal systeem CORTEX : functionele gebieden Zien wat je eigenlijk niet ziet Orienteringsgedrag

7 VISUELE BAAN Creatief kijken 37 Zodoende leidt een letsel in de bovenste linker hersenkwab achteraan tot. gezichtsveldverlies rechts onder in beide ogen. Primair visueel systeem Op de visuele hersenschors mooie weergave van het netvlies Geeft omtrek, bestaan van een voorwerp aan Info aan verderop liggende gebieden is nodig voor interpretatie 6/6 6/18 These simulated visual acuities show how detail is lost with reduced acuity Postgraduaat /120 6/500

8 These simulated contrast sensitivities show that the detail is present, but the picture is washed out Creatief kijken 44 Newborn babies have a preference for the way living things move Postgraduaat

9 Form coherence stimulus Postgraduaat Motion coherence stimulus Creatief kijken 52 Postgraduaat

10 Zien en doen is een mirakel Postgraduaat Postgraduaat 2010 Color perception Bilateral representation Representation in V1 and V4 Children with CVI and CP prefer Color over grey Moving over nonmoving stimuli Color over moving stimuli Color/movement conjunctions over color or movement alone Postgraduaat

11 Maturatie bij kinderen Maturatie van de visus Attention From 2 months onward Object perception From 4 months (cfr BSID-II) Line orientation (?) Colour perception (?) Facial recognition From birth Motion perception biological motion from 8 months onward Visuomotor integration From 2 months onward Newborn babies have a preference for the way living things move Belangrijke basisvaardigheden Detectie Aandacht Herkenning Interpretatie Gevolgen uitval visueel-cognitief Dorsale stroom (parietaal) Gestoorde simultaanperceptie Problemen met waarnemen van bewegende voorwerpen Problemen met bewegen in 3D Gestoorde ooghandcoordinatie Crowding

12 Gevolgen uitval visueel-cognitief Ventrale stroom rechts Gestoorde orientatie (topografische agnosie) Gestoorde herkenning van (mimiek van) gezichten Ventrale stroom links Gestoorde vormherkenning Gestoord lezen Oorzaken Tekort aan zuurstof/bloedsvoorziening voor, rond of kort na de geboorte Craniaal trauma Infecties van de hersenen en hersenvliezen Stofwisselingsstoornissen Gestoorde aanleg van de hersenen Syndromen (VeloCardioFaciaal Syndroom, Williams) 68 Diagnosestelling anno 2009 Oogheelkundig onderzoek Kinderneurologisch onderzoek Neuropsychologisch onderzoek IQ profiel Visueel profiel Gestandaardiseerde neuropsychologische testbatterijen Structureel hersenonderzoek Hersenfunctie-onderzoek Oogartsonderzoek Van het oog tot voor de cortex Lichtreflex Breking van de lens Bijziend/ verziend Fundus Oogzenuw: verdunning geeft aanleiding tot verminderde gezichtsscherpte Gezichtsscherpte en gezichtsveld Kleurenzicht Contrastgevoeligheid 69 Detectie Orientatie!

13 Visual crowding Geassocieerde oogproblemen (65%) occurs when a visual object (such as a letter) is surrounded by other similar objects. As a result, these objects are harder to identify. Verminderde gezichtsscherpte Geeft weer in hoeverre het visueel systeem in staat is om details waar te nemen Nl 10/10; slechtziend 3/10; blind 1/20 Vergelijking raster - optotypes Gezichtsveld Deel van de buitenwereld dat we kunnen zien als we een punt fixeren Geassocieerde oogproblemen Scheelzien Functioneel ElektroRetinoGram (netvlies) VEP (hersenactiviteit) Schokkende oogbewegingen (nystagmus) CORRECTIE INDIEN MOGELIJK Kinderneurologisch onderzoek Neurologisch onderzoek Somatisch onderzoek Globale ontwikkeling Motorische vaardigheden Grof Fijn Oogvolgbewegingen NMR van de hersenen Beschadiging van de witte stof Cysten of zones van weefselverlies in de grijze stof Grootte van de hersenkamers Stoornis in de aanleg van de hersenen 77

14 CVI-kliniek Newly defined sum score Kinderneurologisch onderzoek Oogonderzoek Neuropsychologische testing L-94 Computertaakjes met hoge visueel perceptuele belasting Gezichtsherkenningstaak 09/12/2011 Cerebral Visual Impairment 80

15 TVPS- DTVP Figure ground Form coherence stimulus Motion coherence stimulus Visual closure Form constancy Visual memory 86 VBA data (term (10) ~ preterm (20)) Is interventie zinvol? Geen leeftijdsgrens Kinderen voordeel van de twijfel geven Doel = vergroten wendbaarheid van het visueel systeem Stimuleren Faciliteren Compenseren 09/12/2011 Cerebral Visual Impairment 89

16 Begeleidingsmogelijkheden Thuisbegeleiding Ganspoel Spermalie GON-begeleiding vanuit type 6 Buitengewoon onderwijs type 6 specifiek volgens individuele mogelijkheden/moeilijkheden ISBN: