A systematic review on ‘Foveal Crowding’ in visually impaired children and perceptual learning as a method to reduce Crowding
نویسندگان
چکیده
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 1.5-3× 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 2× larger than those seen adults with NV. The magnitude of the crowding effect is also 2× as large in individuals with CN as in individuals with NV. Finally, children with CVI experience a magnitude of the crowding effect that is 3× 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.
منابع مشابه
A Qualitative Meta-analysis of Perceptual-motor Problems in Visually Impaired People
Introduction: Perceptual motor activities improve motor skills and learning. These skills play an effective role in receiving, interpreting and responding to the sensory stimuli. This study aimed to identify perceptual-motor problems in visually impaired people. Methods: This qualitative research was conducted using a research synthesis method. Therefore, the analysis unit consisted of all the...
متن کاملPerceptual learning in children with visual impairment improves near visual acuity.
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. 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 perc...
متن کاملThe evaluation of reading problems in hearing impaired students: A systematic review of past studies
Abstract Background and Aim: The aim of this systematic review was to investigate the characteristics of deaf and hard of hearing students with reading difficulties. Methods: The research method was a systematic review of the statistical population including all internal and external researches that used the keywords of deaf and hard of hearing students and reading problems in the database...
متن کاملPerceptual learning improves contrast sensitivity, visual acuity, and foveal crowding in amblyopia.
BACKGROUND Amblyopic observers present abnormal spatial interactions between a low-contrast sinusoidal target and high-contrast collinear flankers. It has been demonstrated that perceptual learning (PL) can modulate these low-level lateral interactions, resulting in improved visual acuity and contrast sensitivity. OBJECTIVE We measured the extent and duration of generalization effects to vari...
متن کاملA systematic review and Qualitative meta-analysis on the Identification patterns in Specific Learning Disorder
An accurate identification serves as the pathway that can guide the therapist towards the ultimate goal of adopting appropriate therapeutic and rehabilitation methods. Therefore, the present study aimed to systematically review and qualitative meta-analysis on the identification patterns in Specific Learning Disorder (SLD). The data in this qualitative meta-analysis was all study related to key...
متن کامل