LONGITUDINAL STUDY OF RPE65-ASSOCIATED INHERITED RETINAL DEGENERATIONS

PURPOSE: To study the disease course of RPE65-associated inherited retinal degenerations (IRDs) as a function of the genotype, define a critical age for blindness, and identify potential modifiers. METHODS: Forty-five patients with IRD from 33 families with biallelic RPE65 mutations, 28 stemming from a genetic isolate. We collected retrospective data from medical charts. Coexisting variants in 108 IRD-associated genes were identified with Molecular Inversion Probe analysis. RESULTS: Most patients were diagnosed within the first years of life. Daytime visual function ranged from near-normal to blindness in the first four decades and met WHO criteria for blindness for visual acuity and visual field in the fifth decade. p.(Thr368His) was the most common variant (54%). Intrafamilial variability and interfamilial variability in disease severity and progression were observed. Molecular Inversion Probe analysis confirmed all RPE65 variants and identified one additional variant in LRAT and one in EYS in two separate patients. CONCLUSION: All patients with RPE65-associated IRDs developed symptoms within the first year of life. Visual function in childhood and adolescence varied but deteriorated inevitably toward blindness after age 40. In this study, genotype was not predictive of clinical course. The variance in severity of disease could not be explained by double hits in other IRD genes

LONGITUDINAL STUDY OFRPE65-ASSOCIATED INHERITED RETINAL DEGENERATIONS

Purpose: To study the disease course ofRPE65-associated inherited retinal degenerations (IRDs) as a function of the genotype, define a critical age for blindness, and identify potential modifiers. Methods: Forty-five patients with IRD from 33 families with biallelicRPE65mutations, 28 stemming from a genetic isolate. We collected retrospective data from medical charts. Coexisting variants in 108 IRD-associated genes were identified with Molecular Inversion Probe analysis. Results: Most patients were diagnosed within the first years of life. Daytime visual function ranged from near-normal to blindness in the first four decades and met WHO criteria for blindness for visual acuity and visual field in the fifth decade. p.(Thr368His) was the most common variant (54%). Intrafamilial variability and interfamilial variability in disease severity and progression were observed. Molecular Inversion Probe analysis confirmed allRPE65variants and identified one additional variant inLRATand one inEYSin two separate patients. Conclusion: All patients withRPE65-associated IRDs developed symptoms within the first year of life. Visual function in childhood and adolescence varied but deteriorated inevitably toward blindness after age 40. In this study, genotype was not predictive of clinical course. The variance in severity of disease could not be explained by double hits in other IRD genes

A systematic review on 'Foveal Crowding' in visually impaired children and perceptual learning as a method to reduce Crowding

Contains fulltext : 102577.pdf (publisher's version ) (Open Access)Background - This systematic review gives an overview of foveal crowding (the inability to recognize objects due to surrounding nearby contours in foveal vision) and possible interventions. Foveal crowding can have a major effect on reading rate and deciphering small pieces of information from busy visual scenes. Three specific groups experience more foveal crowding than adults with normal vision (NV): 1) children with NV, 2) visually impaired (VI ) children and adults and 3) children with cerebral visual impairment (CVI). The extent and magnitude of foveal crowding as well as interventions aimed at reducing crowding were investigated in this review. The twofold goal of this review is : [A] to compare foveal crowding in children with NV, VI children and adults and CVI children and [B] to compare interventions to reduce crowding. Methods - Three electronic databases were used to conduct the literature search: PubMed, PsycINFO (Ovid), and Cochrane. Additional studies were identified by contacting experts. Search terms included visual perception, contour interaction, crowding, crowded, and contour interactions. Results - Children with normal vision show an extent of contour interaction over an area 1.5-3x as large as that seen in adults NV. The magnitude of contour interaction normally ranges between 1-2 lines on an acuity chart and this magnitude is even larger when stimuli are arranged in a circular configuration. Adults with congenital nystagmus (CN) show interaction areas that are 2x larger than those seen adults with NV. The magnitude of the crowding effect is also 2x as large in individuals with CN as in individuals with NV. Finally, children with CVI experience a magnitude of the crowding effect that is 3x the size of that experienced by adults with NV. Conclusions - The methodological heterogeneity, the diversity in paradigms used to measure crowding, made it impossible to conduct a meta-analysis. This is the first systematic review to compare crowding ratios and it shows that charts with 50% interoptotype spacing were most sensitive to capture crowding effects. The groups that showed the largest crowding effects were individuals with CN, VI adults with central scotomas and children with CVI. Perceptual Learning seems to be a promising technique to reduce excessive foveal crowding effects.14 p

Assessment of near visual acuity in 0–13 year olds with normal and low vision: a systematic review

Contains fulltext : 168206.pdf (publisher's version ) (Open Access)BACKGROUND: The inclusion for rehabilitation of visually impaired children is partly based on the measurement of near vision, but guidelines for near visual acuity assessment are currently lacking. The twofold purpose of this systematic review was to: (i) provide an overview of the impact of the chart design on near visual acuity measured, and (ii) determine the method of choice for near vision assessments in children of different developmental ages. METHODS: A literature search was conducted by using the following electronic databases: PubMed, Cochrane Library, and EMBASE. The last search was run on March 26th 2016. Additional studies were identified by contacting experts and searching for relevant articles in reference lists of included studies. Search terms were: vision test(s), vision assessment(s), visual acuity, chart(s) and near. RESULTS: For children aged 0-3 years the golden standard is still the preferential looking procedure. Norms are available for this procedure for 6-36 month old children. For 4-7 year olds, we recommend using the LEA symbols, because these symbols have been properly validated and can be used in preliterate children. Responses can be verbal or by matching the target symbol. In children aged 8-13 years, the recommended method is the ETDRS letter chart, because letter acuity is more predictive for functional vision and reading than symbol acuity. In 8-13 year olds, letter acuity is 0.1-0.2 logMAR poorer than symbol acuity. CONCLUSIONS: Chart design, viewing distance, and threshold choice have a serious impact on near visual acuity measurements. Near visual acuity measured with symbols is lower than near visual acuity measured with gratings, and near visual acuity measured with letters is lower than near visual acuity measured with symbols. Viewing distance, chart used, and letter spacing should be adapted to the child's development and reported in order to allow comparisons between measurements

Eye Movements, Strabismus, Amblyopia and Neuro-Ophthalmology Perceptual Learning in Children With Infantile Nystagmus: Effects on 2D Oculomotor Behavior

Citation: Huurneman B, Boonstra FN, Goossens J. Perceptual learning in children with infantile nystagmus: effects on 2D oculomotor behavior. Invest Ophthalmol Vis Sci. 2016;57: 2016;57:4229-4238. DOI:10.1167/ iovs.16-19555 PURPOSE. To determine changes in oculomotor behavior after 10 sessions of perceptual learning on a letter discrimination task in children with infantile nystagmus (IN). METHODS. Children with IN (18 children with idiopathic IN and 18 with oculocutaneous albinism accompanied by IN) aged 6 to 11 years were divided into two training groups matched on diagnosis: an uncrowded training group (n ¼ 18) and a crowded training group (n ¼ 18). Target letters always appeared briefly (500 ms) at an eccentric location, forcing subjects to quickly redirect their gaze. Training occurred twice per week for 5 consecutive weeks (3500 trials total). Norm data and test-retest values were collected from children with normal vision (n ¼ 11). Outcome measures were: nystagmus characteristics (amplitude, frequency, intensity, and the expanded nystagmus acuity function); fixation stability (the bivariate contour ellipse area and foveation time); and saccadic eye movements (latencies and accuracy) made during a simple saccade task and a crowded letter-identification task. RESULTS. After training, saccadic responses of children with IN improved on the saccade task (latencies decreased by 14 6 4 ms and gains increased by 0.03 6 0.01), but not on the crowded letter task. There were also no training-induced changes in nystagmus characteristics and fixation stability. Although children with normal vision had shorter latencies in the saccade task (47 6 14 ms at baseline), test-retest changes in their saccade gains and latencies were almost equal to the training effects observed in children with IN. CONCLUSIONS. Our results suggest that the improvement in visual performance after perceptual learning in children with IN is primarily due to improved sensory processing rather than improved two-dimensional oculomotor behavior

Practice makes perfect:Crowdingtraining improves visual functions in children with visual impairment

Crowding is a visual perceptual phenomenon that refers to impaired ability to recognize a suprathreshold object when it is presented in the vicinity of other objects. Crowding therefore poses a limit on object recognition. The phenomenon is regarded to be one of the reasons why young children need large textbook letters. Several studies have provided evidence that crowding imposes a bottleneck on reading speed, and reading long words. Thus, crowding influences visual perception and object recognition in young children. Recent studies show that crowding is stronger in children with visual impairment than in children with normal vision. But which factors are responsible for these strong crowding effects? And how can we reduce crowding in children with visual impairment for whom low visual acuity in itself already poses a bottleneck on object recognition? This review article tries to answer these questions. This knowledge is useful for educational psychologists, because crowding can interfere with the acquisition of academic skills and reading. Keywords: crowding, learning, visual impairment, visual acuity, visual attention.<br/

Perceptual Learning in Children With Visual Impairment Improves Near Visual Acuity

<p>PURPOSE. This study investigated whether visual perceptual learning can improve near visual acuity and reduce foveal crowding effects in four-to nine-year-old children with visual impairment.</p><p>METHODS. Participants were 45 children with visual impairment and 29 children with normal vision. Children with visual impairment were divided into three groups: a magnifier group (n = 12), a crowded perceptual learning group (n = 18), and an uncrowded perceptual learning group (n = 15). Children with normal vision also were divided in three groups, but were measured only at baseline. Dependent variables were single near visual acuity (NVA), crowded NVA, LH line 50% crowding NVA, number of trials, accuracy, performance time, amount of small errors, and amount of large errors. Children with visual impairment trained during six weeks, two times per week, for 30 minutes (12 training sessions).</p><p>RESULTS. After training, children showed significant improvement of NVA in addition to specific improvements on the training task. The crowded perceptual learning group showed the largest acuity improvements (1.7 logMAR lines on the crowded chart, P <0.001). Only the children in the crowded perceptual learning group showed improvements on all NVA charts.</p><p>CONCLUSIONS. Children with visual impairment benefit from perceptual training. While task-specific improvements were observed in all training groups, transfer to crowded NVA was largest in the crowded perceptual learning group. To our knowledge, this is the first study to provide evidence for the improvement of NVA by perceptual learning in children with visual impairment. (http://www.trialregister.nlnumber,NTR2537.)</p>

Measurement of fine-motor skills in young children with visual impairment

Insight into the typical motor development of children with visual impairment (VI) is necessary in order to recognise whether children with VI are at risk of motor developmental problems, and to evaluate the effectiveness of exercise interventions. In 2003 the ManuVis was published with reference values for children with VI of ages from 6 to 11 years. This paper reports on a follow-up study of the ManuVis focused on: a) comparison of fine motor skills between children with VI and normal sighted (NS) children; b) sampling norm-references for children with VI in the 4-11 years age range to increase validity; and c) test-retest and inter-rater reliability. In total 256 children with VI and 162 NS children were included in the study. The results demonstrated that children with VI needed significantly more time than NS children to perform all test items, especially at younger ages. Performance time decreased in both children with VI and NS children from the younger to the older age groups, but NS children reached their minimum at a younger age. Test-retest reliability on the items varied from moderate to excellent and inter-rater reliability was excellent. The results suggest that children with VI have slower and more prolonged motor learning than NS children. The ManuVis differentiates between typical and atypical fine-motor performance of children with VI between 4 and 9 years of age, and is useful for monitoring fine-motor skills in children with VI from 4 years to (at least) 11 years.<br/

Test-retest and inter- and intrareliability of the quality of the upper-extremity skills test in preschool-age children with cerebral palsy

Objective: To investigate the test-retest, inter-, and intraobserver reliability of the Quality of Upper Extremity Skills Test (QUEST) in young children with cerebral palsy (CP). Design: For test-retest reliability, a test-retest design was used; for the intra- and interobserver reliability, the videotaped test was scored on 2 occasions by 1 observer and by various observers. Setting: Groups of preschool-age children in 2 general rehabilitation centers. Participants: Twenty-one children with CP (12 boys, 9 girls) aged 2 to 4.5 years (mean, 39mo). Interventions: Not applicable. Main Outcome Measure: Spearman correlation coefficient. Results: The data indicated that test-retest reliability was strong (rho range,.85-.94). Intraobserver agreement (rho range,.63-.95) and agreement between various observers (rho range,.72-.90) were moderate to strong. Conclusions: Test-retest and inter- and intraobserver reliability of the QUEST in preschool-age children with CP is good