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Graefe's Archive For Clinical and... May 2023Amblyopia is a neurodevelopmental disorder characterized by functional deficits in the visual cortex. Functional magnetic resonance imaging (fMRI) is the most commonly... (Review)
Review
Amblyopia is a neurodevelopmental disorder characterized by functional deficits in the visual cortex. Functional magnetic resonance imaging (fMRI) is the most commonly used neuroimaging technique for investigating amblyopia. Herein, we systematically searched a PubMed database from inception to December 2021 to highlight the current progress and promises about fMRI technology in amblyopia; amblyopia's neural mechanism, the comparison of different types of amblyopia, and the evaluation of the therapeutic effect were explored. Relevant articles published in English and appropriate cross-references were considered for inclusion, including basic studies, imaging techniques, clinical diagnostic and therapeutic studies, case series, and reviews.
Topics: Humans; Amblyopia; Visual Cortex; Magnetic Resonance Imaging
PubMed: 36282454
DOI: 10.1007/s00417-022-05826-z -
Clinical & Experimental Optometry Nov 2019Aniseikonia is a difference in the perceived size or shape of images between eyes, and can arise from a variety of physiological, neurological, retinal, and optical... (Review)
Review
Aniseikonia is a difference in the perceived size or shape of images between eyes, and can arise from a variety of physiological, neurological, retinal, and optical causes. Aniseikonia is associated with anisometropia, as both anisometropia itself and the optical correction for anisometropia can cause aniseikonia. Image size differences above one to three per cent can be clinically symptomatic. Common symptoms include asthenopia, headache and diplopia in vertical gaze. Size differences of three and more impair binocular visual functions such as binocular summation and stereopsis. Above five per cent of aniseikonia, binocular inhibition or suppression tend to occur to prevent diplopia and confusion. Aniseikonia can be measured using a range of techniques and can be corrected or reduced by prescribing contact lenses or specially designed spectacle lenses. Subjective testing of aniseikonia is the only way to accurately measure the overall perceived amount of aniseikonia. However, currently it is not routinely assessed in most clinical settings. At least two-thirds of patients with amblyopia have anisometropia, thus we may expect aniseikonia to be common in patients with anisometropic amblyopia. However, aniseikonia may not be experienced by the patient under normal binocular viewing conditions if the image from the amblyopic eye is of poor quality or is too strongly suppressed for image size differences to be recognised. This lack of binocular simultaneous perception in amblyopia may also prevent the measurement of aniseikonia, as most common techniques require direct comparisons of images seen by each eye. Current guidelines for the treatment of amblyopia advocate full correction of anisometropia to equalise image clarity, but do not address aniseikonia. Significant image size differences between eyes may lead to suppression and abnormal binocular adaptations. It is possible that correcting anisometropia and aniseikonia simultaneously, particularly at the initial diagnosis of anisometropia, would reduce the need to develop suppression and improve treatment outcomes for anisometropic amblyopia.
Topics: Amblyopia; Aniseikonia; Anisometropia; Humans
PubMed: 30791133
DOI: 10.1111/cxo.12881 -
Investigative Ophthalmology & Visual... Feb 2021Amblyopes suffer a defect in temporal processing, presumably because of a neural delay in their visual processing. By measuring flash-lag effect (FLE), we investigate...
PURPOSE
Amblyopes suffer a defect in temporal processing, presumably because of a neural delay in their visual processing. By measuring flash-lag effect (FLE), we investigate whether the amblyopic visual system could compensate for the intrinsic neural delay due to visual information transmissions from the retina to the cortex.
METHODS
Eleven adults with amblyopia and 11 controls with normal vision participated in this study. We assessed the monocular FLE magnitude for each subject by using a typical FLE paradigm: a bar moved horizontally, while a flashed bar briefly appeared above or below it. Three luminance contrasts of the flashed bar were tested: 0.2, 0.6, and 1.
RESULTS
All participants, controls and those with amblyopia, showed a typical FLE. However, the FLE magnitude of participants with amblyopia was significantly shorter than that of the control participants, for both their amblyopic eye (AE) and fellow eye (FE). A nonsignificant difference was found in FLE magnitude between the AE and the FE.
CONCLUSIONS
We demonstrate a reduced FLE both in the AE as well as the FE of patients with amblyopia, suggesting a global visual processing deficit. We suggest it may be attributed to a more limited spatiotemporal extent of facilitatory anticipatory activity within the amblyopic primary visual cortex.
Topics: Adult; Aged; Amblyopia; Female; Humans; Male; Middle Aged; Retina; Visual Acuity; Visual Cortex; Young Adult
PubMed: 33599734
DOI: 10.1167/iovs.62.2.23 -
European Journal of Ophthalmology Jan 2022The most common cause of vision impairment in children is amblyopia. It is defined as impaired visual acuity in one or both eyes that is present with no demonstrable...
The most common cause of vision impairment in children is amblyopia. It is defined as impaired visual acuity in one or both eyes that is present with no demonstrable abnormality of the visual pathway and is not immediately resolved by wearing glasses. After the World Health Organization (WHO) recognized COVID-19 as a global pandemic on March 11, 2020, widespread changes and restrictions to social and sanitary practices have presented significant issues in access to eye care during the COVID-19 pandemic. A reduction of more than 80% in pediatric eye care volume up to its total cessation has been observed in different departments. In this scenario, reduced or absent eyesight, due to delay in timely treatment of amblyopic conditions, could create major, long-lasting effects on all aspects of life, including daily personal activities, interacting with the community, school and work opportunities and the ability to access public services. Processes coming out of lockdown should be gradually easing restrictions giving priority to ophthalmology and eye care facilities so that amblyopia does not remain unattended and irreversible as in adults due to lack of timely treatments. If not reversible, this process could lead to a dramatic increase in disability and unsustainable social costs for many governments.
Topics: Adult; Amblyopia; COVID-19; Child; Communicable Disease Control; Disease Outbreaks; Humans; Myopia; Pandemics; SARS-CoV-2
PubMed: 34751045
DOI: 10.1177/11206721211053175 -
Strabismus Mar 2023The objective of this review was to estimate the prevalence of strabismus and amblyopia in Africa. A systematic online literature search was conducted for articles on... (Meta-Analysis)
Meta-Analysis
The objective of this review was to estimate the prevalence of strabismus and amblyopia in Africa. A systematic online literature search was conducted for articles on strabismus and amblyopia in Africa. Meta-analysis was performed, using the Freeman-Tukey double arcsine transformation, to estimate the prevalence of strabismus and amblyopia in Africa. Subgroup analyses were conducted according to age, gender, study year, and type of amblyopia. Meta-regression was used to evaluate the influence of predetermined factors on the prevalence of amblyopia. 8 (1 population-based & 7 school-based) and 21 (3 population-based & 18 school-based) studies on strabismus and amblyopia with sample sizes of 22,355 and 46,841, respectively, were included in the review. Overall prevalence of strabismus in Africa was estimated to be 0.8% (95% CI: 0.4% - 1.4%); exotropia was 0.2% (95% CI: 0.1% - 0.5%) and esotropia was 0.5% (95% CI: 0.1% - 1.2%). Overall prevalence of amblyopia was estimated to be 0.6% (95% CI: 0.3% - 0.9%); refractive and strabismic amblyopia were 1.1% (95% CI: 0.2% - 2.5%) and 0.4% (95% CI: 0.2% - 0.6%), respectively. Prevalence estimate of amblyopia in males was 1.8% (95% CI: 0.7% - 3.3%) and in females was 1.3% (95% CI: 0.4% - 2.6%). There was a significant association between the prevalence of amblyopia and the type of amblyopia (p = .007) and the study year (p = .006). Although there appears to be a relatively low prevalence of strabismus and amblyopia in Africa, there is a dearth of well-designed population-based studies on strabismus and amblyopia in Africa, resulting in the lack of epidemiological information on strabismus and amblyopia within the general African population. Information about the prevalence of strabismus and amblyopia across Africa can inform policy making and design and implementation of public health intervention program.
Topics: Male; Female; Humans; Amblyopia; Visual Acuity; Strabismus; Esotropia; Prevalence; Africa
PubMed: 36576233
DOI: 10.1080/09273972.2022.2157023 -
International Ophthalmology Mar 2023To analyze the top 100 most cited papers related to amblyopia. (Review)
Review
AIM
To analyze the top 100 most cited papers related to amblyopia.
METHODS
A bibliographic search in the Institute for Scientific Information Web of Knowledge across 55 years was performed.
RESULTS
Eighty-nine of the 100 papers were published in first-quartile journals. Half (50) of the senior authors were from the USA. Most papers dealt with clinical science (72) and included original research (84). Forty-two of the articles related to all three types of amblyopia (refractive, strabismic and deprivation). Thirty-four related to both strabismic and refractive amblyopia. Around two-thirds of the papers dealt with treatment (34) and pathophysiology (30). Almost a quarter (23%) of the papers were multicenter studies. Nearly half (48) of the papers were published between 2000 and 2010. The Pediatric Eye Disease Investigator Group (PEDIG) published the highest number of studies (11), which dealt more with treatment (p = 0.01) and had higher average number of citations per years (p = 0.05). A larger number of articles on the treatment of amblyopia are newer (p = 0.01). There was no correlation between the time of their publication and the number of citations (p = 0.68, r = 0.042).
CONCLUSIONS
Half of the papers were published between 2000 and 2010 and were spearheaded by PEDIG. Most papers dealt with treatment and pathophysiology. This study provides an important historical perspective, emphasizing the need for additional research to better understand this preventable and curable childhood vision impairment.
Topics: Child; Humans; Amblyopia; Refraction, Ocular; Vision Tests
PubMed: 36057007
DOI: 10.1007/s10792-022-02487-z -
Journal of Binocular Vision and Ocular... 2020Amblyopia is a common perceptual disorder resulting from abnormal visual input during development. The clinical presentation and visual deficits associated with... (Review)
Review
Amblyopia is a common perceptual disorder resulting from abnormal visual input during development. The clinical presentation and visual deficits associated with amblyopia are well characterized. Less is known however, about amblyopia's impact on the central nervous system (CNS). While early insights into the neuropathophysiology of amblyopia have been based on findings from animal models and postmortem human studies, recent advances in noninvasive magnetic resonance imaging (MRI) techniques have enabled the study of amblyopia's effects . We review recent retinal and neuroimaging research documenting amblyopia's structural and functional impact on the CNS. Clinical imaging provides some evidence for retinal and optic nerve abnormalities in amblyopic eyes, although the overall picture remains inconclusive. Neuroimaging studies report clearer changes in both structure and function of the visual pathways. In the optic nerves, optic tracts, and optic radiations of individuals with amblyopia, white-matter integrity is decreased. In the lateral geniculate nuclei, gray matter volume is decreased and neural activity is reduced. Reduced responses are also seen in the amblyopic primary visual cortex and extrastriate areas. Overall, amblyopia impacts structure and function at multiple sites along the visual processing hierarchy. Moreover, there is some evidence that amblyopia's impact on the CNS depends on its etiology, with different patterns of results for strabismic and anisometropic amblyopia. To clarify the impact of amblyopia on the CNS, simultaneous collection of retinal, neural, and perceptual measures should be employed. Such an approach will help (1) distinguish cause and effect of amblyopic impairments, (2) separate the impact of amblyopia from other superimposed conditions, and (3) identify the importance of amblyopic etiology to specific neural and perceptual deficits.
Topics: Amblyopia; Anisometropia; Central Nervous System; Humans; Magnetic Resonance Imaging; Strabismus; Tomography, Optical Coherence
PubMed: 33206009
DOI: 10.1080/2576117X.2020.1841710 -
Developmental Psychobiology May 2022Past research has reported deficits on reaching and grasping tasks in adults with amblyopia and degraded stereoacuity, but less is known about visuomotor deficits in...
Past research has reported deficits on reaching and grasping tasks in adults with amblyopia and degraded stereoacuity, but less is known about visuomotor deficits in children-specifically, for complex tasks that require movement sequencing. This study therefore compared the visuomotor performance in 21 children with abnormal binocular vision (patient group) due to amblyopia and/or strabismus to that of 236 children with normal binocular vision development (control group) ages 5-14 years. Visual acuity, stereoacuity, and hand-movement kinematics on a bead-threading task were assessed. The patient group showed significantly longer durations than the control group on grasp, thread, and total movement durations. Both groups of participants were then split into immature (ages 5-9 years) and mature (ages 10-14 years) groups based on the maturation age for these parameters in control children. Grasp duration was longer in both mature and immature patient groups; thread and total movement durations were longer in the mature patient group only. Grasp duration was the most disrupted kinematic parameter in children with disrupted binocular vision due to amblyopia and/or strabismus, regardless of age. The level of stereoacuity loss rather than the depth of visual acuity loss was associated with the severity of visuomotor deficits.
Topics: Adolescent; Adult; Amblyopia; Child; Child, Preschool; Humans; Psychomotor Performance; Strabismus; Vision, Binocular; Visual Acuity
PubMed: 35452551
DOI: 10.1002/dev.22270 -
European Journal of Ophthalmology Jul 2023Amblyopia is the decreased best-corrected visual acuity (BCVA) in one or both eyes caused by the abnormal processing of visual input during development. One common cause... (Review)
Review
Amblyopia is the decreased best-corrected visual acuity (BCVA) in one or both eyes caused by the abnormal processing of visual input during development. One common cause of amblyopia is anisometropia, which has attracted widespread attention. Many structural changes occur in the primary and extrastriate visual areas of the cerebral cortex, as well as in the eyes, in patients with anisometropic amblyopia. Understanding these mechanisms has provided a favorable theoretical basis for treating anisometropic amblyopia. This article reviews the functional and anatomical changes and progress toward the treatment of anisometropic amblyopia.
Topics: Humans; Amblyopia; Visual Acuity; Eye; Anisometropia
PubMed: 36448184
DOI: 10.1177/11206721221143164 -
Survey of Ophthalmology 2023Amblyopia is a global public health issue with extensive, multifaceted impacts on vision and quality of life (QoL) for both patients and families. Geographical variation... (Review)
Review
Amblyopia is a global public health issue with extensive, multifaceted impacts on vision and quality of life (QoL) for both patients and families. Geographical variation exists in the management of amblyopia, with traditional mainstay treatments, optical correction, and fellow eye occlusion most successful when implemented at an early age. In recent years, however, studies demonstrating meaningful improvements in older children and adults have challenged the concept of a complete loss of visual processing plasticity beyond the critical period of visual development, with growing evidence supporting the potential efficacy of emerging, more engaging, binocular therapies in both adults and children. Binocular approaches aim to restore deficits in amblyopia that extend beyond monocular visual acuity impairment, including binocular fusion and visuomotor skills. In view of this, incorporating outcome measures that evaluate the visual performance and functional ability of individuals with amblyopia will provide a clearer understanding of the effect of amblyopia on QoL and a more comprehensive evaluation of amblyopia therapies.
Topics: Adult; Child; Humans; Amblyopia; Quality of Life; Vision, Binocular; Visual Acuity
PubMed: 36681277
DOI: 10.1016/j.survophthal.2023.01.001