Relationship of visual cortex function and visual acuity in anisometropic amblyopic children

Integrative neurovascular coupling and neurotransmitter analyses in anisometropic and visual deprivation amblyopia children

The association between visual abnormalities and impairments in cerebral blood flow and brain region potentially results in neural dysfunction of amblyopia. Nevertheless, the differences in the complex mechanisms of brain neural network coupling and its relationship with neurotransmitters remain unclear. Here, the neurovascular coupling mechanism and neurotransmitter activity in children with anisometropic amblyopia (AA) and visual deprivation amblyopia (VDA) was explored. The neurovascular coupling of 17 brain regions in amblyopia children was significantly abnormal than in normal controls. The classification abilities of coupling units in brain regions differed between two types of amblyopia. Correlations between different coupling effects and neurotransmitters were different. The findings of this study demonstrate a correlation between the neurovascular coupling and neurotransmitter in children with AA and VDA, implying their impaired neurovascular coupling function and potential molecular underpinnings. The neuroimaging evidence revealed herein offers potential for the development of neural therapies for amblyopia.

Structural and functional alterations in the brains of patients with anisometropic and strabismic amblyopia: a systematic review of magnetic resonance imaging studies

Amblyopia is the most common cause of vision loss in children and can persist into adulthood in the absence of effective intervention. Previous clinical and neuroimaging studies have suggested that the neural mechanisms underlying strabismic amblyopia and anisometropic amblyopia may be different. Therefore, we performed a systematic review of magnetic resonance imaging studies investigating brain alterations in patients with these two subtypes of amblyopia; this study is registered with PROSPERO (registration ID: CRD42022349191). We searched three online databases (PubMed, EMBASE, and Web of Science) from inception to April 1, 2022; 39 studies with 633 patients (324 patients with anisometropic amblyopia and 309 patients with strabismic amblyopia) and 580 healthy controls met the inclusion criteria (e.g., case-control designed, peer-reviewed articles) and were included in this review. These studies highlighted that both strabismic amblyopia and anisometropic amblyopia patients showed reduced activation and distorted topological cortical activated maps in the striate and extrastriate cortices during task-based functional magnetic resonance imaging with spatial-frequency stimulus and retinotopic representations, respectively; these may have arisen from abnormal visual experiences. Compensations for amblyopia that are reflected in enhanced spontaneous brain function have been reported in the early visual cortices in the resting state, as well as reduced functional connectivity in the dorsal pathway and structural connections in the ventral pathway in both anisometropic amblyopia and strabismic amblyopia patients. The shared dysfunction of anisometropic amblyopia and strabismic amblyopia patients, relative to controls, is also characterized by reduced spontaneous brain activity in the oculomotor cortex, mainly involving the frontal and parietal eye fields and the cerebellum; this may underlie the neural mechanisms of fixation instability and anomalous saccades in amblyopia. With regards to specific alterations of the two forms of amblyopia, anisometropic amblyopia patients suffer more microstructural impairments in the precortical pathway than strabismic amblyopia patients, as reflected by diffusion tensor imaging, and more significant dysfunction and structural loss in the ventral pathway. Strabismic amblyopia patients experience more attenuation of activation in the extrastriate cortex than in the striate cortex when compared to anisometropic amblyopia patients. Finally, brain structural magnetic resonance imaging alterations tend to be lateralized in the adult anisometropic amblyopia patients, and the patterns of brain alterations are more limited in amblyopic adults than in children. In conclusion, magnetic resonance imaging studies provide important insights into the brain alterations underlying the pathophysiology of amblyopia and demonstrate common and specific alterations in anisometropic amblyopia and strabismic amblyopia patients; these alterations may improve our understanding of the neural mechanisms underlying amblyopia.

Amblyopia: progress and promise of functional magnetic resonance imaging

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.

Investigation of Altered Spontaneous Brain Activities in Patients With Moyamoya Disease Using Percent Amplitude of Fluctuation Method: A Resting-State Functional MRI Study

Background: Moyamoya disease (MMD) is a chronic progressive cerebrovascular abnormality characterized by chronic occlusion of large intracranial vessels with smoky vascular development at the base of the skull. In patients with MMD, abnormal spontaneous brain activity would be expected. Purpose: To assess the brain activity changes in patients with MMD by resting-state functional MRI (rs-fMRI), using the percent amplitude of fluctuation (PerAF) analysis method. Materials and Methods: A total of 17 patients with MMD (3 males and 14 females) and 17 healthy control (HC) subjects with matched gender and age were recruited for this study. We used rs-fMRI to scan all the patients with MMD. Spontaneous neural activity was evaluated using the PerAF approach. The receiver operating characteristic (ROC) curve analysis was used to assess the ability of the PerAF to distinguish patients with MMD from HCs. The Hospital Anxiety and Depression Scale (HADS) tests were performed to assess the emotional status of patients with MMD and retinal nerve fiber layer thickness (RNFLT) was measured using high-resolution optical coherence tomography (hr-OCT). The relationship between the HADS scores, RNFLT values, and the PerAF signals was assessed using the Pearson's correlation analysis. Results: Compared with HCs, the PerAF signals in patients with MMD were decreased in the Frontal_Sup_Medial_R and Precentral_L, whereas those in the Caudate_L were increased. The areas under the ROC curves indicated that signals in these brain regions could distinguish between patients with MMD and HCs. The PerAF value of Frontal_Sup_Medial_R was positively correlated with the left and right eye RNFLT values and negatively correlated with the HADS scores. Conclusion: In patients with MMD, reduced PerAF signals in the Frontal_Sup_Medial_R, Precentral_L, and Caudate_L may be associated with psychiatric diseases including anxiety and depression and decreased RNFLT may be associated with ophthalmic complications due to the compression of terminal branches of the internal carotid artery in the retinal fiber layer. The PerAF can be used as an effective indicator of ocular complications of MMD and to study the neural mechanism underpinning emotional complications in patients with MMD.

Altered Effective Connectivity of Children and Young Adults With Unilateral Amblyopia: A Resting-State Functional Magnetic Resonance Imaging Study

The altered functional connectivity (FC) in amblyopia has been investigated by many studies, but the specific causality of brain connectivity needs to be explored further to understand the brain activity of amblyopia. We investigated whether the effective connectivity (EC) of children and young adults with amblyopia was altered. The subjects included 16 children and young adults with left eye amblyopia and 17 healthy controls (HCs). The abnormalities between the left/right primary visual cortex (PVC) and the other brain regions were investigated in a voxel-wise manner using the Granger causality analysis (GCA). According to the EC results in the HCs and the distribution of visual pathways, 12 regions of interest (ROIs) were selected to construct an EC network. The alteration of the EC network of the children and young adults with amblyopia was analyzed. In the voxel-wise manner analysis, amblyopia showed significantly decreased EC between the left/right of the PVC and the left middle frontal gyrus/left inferior frontal gyrus compared with the HCs. In the EC network analysis, compared with the HCs, amblyopia showed significantly decreased EC from the left calcarine fissure, posterior cingulate gyrus, left lingual gyrus, right lingual gyrus, and right fusiform gyrus to the right calcarine fissure. Amblyopia also showed significantly decreased EC from the right inferior frontal gyrus and right lingual gyrus to the left superior temporal gyrus compared with the HCs in the EC network analysis. The results may indicate that amblyopia altered the visual feedforward and feedback pathway, and amblyopia may have a greater relevance with the feedback pathway than the feedforward pathway. Amblyopia may also correlate with the feedforward of the third visual pathway.

Altered spontaneous brain activity in patients with strabismic amblyopia: A resting-state fMRI study using regional homogeneity analysis

The present study aimed to compare the regional homogeneity (ReHo) of resting-state brain function between subjects with strabismic amblyopia and normal controls. A total of 12 adult patients with strabismic amblyopia and 34 age- and gender-matched normal controls were enrolled in the present study. All patients were subjected to resting-state magnetic resonance imaging using a Siemens Trio 3.0T magnetic resonance scanner. ReHo values of the whole brain were calculated and standardized. An independent-samples t-test was used to analyze the differences in ReHo values between the two groups. Patients with strabismic amblyopia exhibited reduced ReHo values in certain parts of the occipital lobe, including the lingual gyrus, cuneus and superior occipital gyrus. Increased ReHo values were observed in the precuneus and certain parts of the prefrontal cortex of patients with strabismic amblyopia, including the superior frontal gyrus and middle frontal gyrus. The ReHo index of the precuneus was negatively correlated with age. However, there was no correlation between the ReHo values and the visual acuity of patients with strabismic amblyopia. ROC curve analysis demonstrated that the greatest area under curve (AUC) value was in the medial prefrontal cortex (AUC=0.864). The results of the present study suggested that visual information processing may be impaired in visual areas V1 and V2. Furthermore, adult patients with strabismic amblyopia exhibited brain plasticity that compensated for visuomotor coordination and visuospatial imagery deficits.

Altered cortical morphology of visual cortex in adults with monocular amblyopia

BACKGROUND

The neural mechanism of amblyopia and its impact on the adult brain remain unclear. This hinders effective treatment for adults with this disease.

PURPOSE

To investigate neuroanatomical differences in cortical morphometry between amblyopic adults and healthy controls, and to explore the structural covariance of abnormal morphometric changes.

STUDY TYPE

Prospective.

POPULATION

Twenty-one amblyopic adults and 34 healthy controls.

FIELD STRENGTH/SEQUENCE

3T MRI, T₁ -weighted, MPRAGE sequence.

ASSESSMENT

All participants completed ophthalmologic exams to confirm the diagnosis of amblyopia or its absence in the healthy controls, including tests of ocular motility and dilation, fundus exam, autorefraction and synoptophore tests. Cortical volume, thickness, and surface area measurements were obtained using FreeSurfer software.

STATISTICAL TESTS

Statistical differences of MRI measures between amblyopic adults and healthy controls were identified using a general linear model with intracranial volume and age as covariates. Monte Carlo simulations were used to correct for multiple comparisons. The structural covariance of abnormal morphometric changes and the relationship between morphometric abnormalities and visual acuity of the amblyopic eye were examined.

RESULTS

Compared with healthy controls, amblyopic adults showed reduced cortical volume in left lateral occipital cortex, and decreased cortical thickness in bilateral inferior temporal gyrus and left precentral gyrus (P < 0.05; Monte Carlo corrected). Structural covariance between cortical volume of left lateral occipital cortex and cortical thickness of right inferior temporal gyrus in amblyopic adults was significantly less than in healthy controls (z = 1.73; P < 0.05).

DATA CONCLUSION

Our study identified morphological abnormalities in occipital cortex and in temporal and frontal cortex which are projection fields of visual cortex important for processing of visual form and object location information, and disrupted structural covariance of visual cortex with other brain regions in amblyopic patients.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:1405-1412.

Visual cortex neural activity alteration in cervical spondylotic myelopathy patients: a resting-state fMRI study

PURPOSE

We sought to investigate visual cortex neural activity and functional connectivity (FC) alterations in cervical spondylotic myelopathy (CSM) patients using resting-state fMRI (rs-fMRI) and to explore the relationships of these alterations with visual disorder.

METHODS

Twenty-seven CSM patients and 11 healthy controls were recruited as the study and control groups. The amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo) values were calculated to represent neural activity, seed-based correlation analysis (SCA) was performed to analyze the FC of visual cortex, and the outcomes were compared between groups. The preoperative best-corrected visual acuity (pre-BCVA) and postoperative BCVA (post-BCVA) of study groups were measured. Correlation analyses of the ALFF/ReHo values with the preoperative and postoperative BCVAs were performed. Correlations of the bilateral BCVAs with the ipsilateral and contralateral visual cortex neural activities were performed.

RESULTS

The ALFF/ReHo values were decreased in the occipital lobe and increased in the cerebellar posterior lobe in the study group (P < 0.05). Increased FC was demonstrated between Brodmann's area 17 and posterior cingulate lobe (P < 0.05). Postoperatively, the BCVAs were ameliorated in 22 oculi dexter (ODs) and 20 oculi sinister (OSs) in the study group. Positive correlations between neural activity in the visual cortex and the preoperative and postoperative BCVAs were detected in the study group. The bilateral BCVAs were positively correlated with either the ipsilateral or contralateral visual cortex neural activity.

CONCLUSION

Both ALFF/ReHo value changes and positive correlations of these changes with BCVA were demonstrated in CSM. The FC between the visual cortex and posterior cingulate lobe was also increased in CSM.

Altered spontaneous brain activity patterns in strabismus with amblyopia patients using amplitude of low-frequency fluctuation: a resting-state fMRI study

OBJECTIVE

Previous studies have demonstrated that strabismus or amblyopia can result in markedly brain function and anatomical alterations. However, the differences in spontaneous brain activities of strabismus with amblyopia (SA) patients still remain unclear. This current study intended to use the amplitude of low-frequency fluctuation (ALFF) technique to investigate the intrinsic brain activity changes in SA subjects.

PATIENTS AND METHODS

A total of 16 patients with SA (6 males and 10 females) and 16 healthy controls (HCs; 6 males and 10 females) similarly matched in age, gender, and education status were recruited and examined with the resting-state functional MRI. The spontaneous brain activity changes were investigated using the ALFF technique. The receiver operating characteristic curve was performed to classify the mean ALFF signal values of the SA patients from HCs. The correlations between the ALFF values of distinct brain regions and the clinical manifestations in SA patients were evaluated in terms of the Pearson's correlation analysis.

RESULTS

Compared with HCs, SA patients had significantly decreased ALFF in the left cerebellum posterior lobe, left middle frontal gyrus, and bilateral thalamus. In contrast, SA patients showed increased ALFF values in the right superior frontal gyrus, right precuneus, left cuneus, and bilateral precentral gyrus. Nonetheless, there was no linear correlation between the mean ALFF values in brain regions and clinical features.

CONCLUSION

Diverse brain regions including vision-related and motion-related areas exhibited aberrant intrinsic brain activity patterns, which imply the neuropathologic mechanisms of oculomotor disorder and vision deficit in the SA patients.

Abnormal Spontaneous Brain Activity in Patients With Anisometropic Amblyopia Using Resting-State Functional Magnetic Resonance Imaging

PURPOSE

To explore the abnormality of spontaneous activity in patients with anisometropic amblyopia under resting-state functional magnetic resonance imaging (Rs-fMRI).

METHODS

Twenty-four participants were split into two groups. The anisometropic amblyopia group had 10 patients, all of whom had anisometropic amblyopia of the right eye, and the control group had 14 healthy subjects. All participants underwent Rs-fMRI scanning. Measurement of amplitude of low frequency fluctuations of the brain, which is a measure of the amplitudes of spontaneous brain activity, was used to investigate brain changes between the anisometropic amblyopia and control groups.

RESULTS

Compared with an age- and gender-matched control group, the anisometropic amblyopia group showed increased amplitude of low frequency fluctuations of spontaneous brain activity in the left superior temporal gyrus, the left inferior parietal lobe, the left pons, and the right inferior semi-lunar lobe. The anisometropic amblyopia group also showed decreased amplitude of low frequency fluctuations in the bilateral medial frontal gyrus.

CONCLUSIONS

This study demonstrated abnormal spontaneous brain activities in patients with anisometropic amblyopia under Rs-fMRI, and these abnormalities might contribute to the neuropathological mechanisms of anisometropic amblyopia. [J Pediatr Ophthalmol Strabismus. 2017;54(5):303-310.].

Structural asymmetry of cortical visual areas is related to ocular dominance

The grey matter of the human brain is asymmetrically distributed between the cerebral hemispheres. This asymmetry includes visual areas, but its relevance to visual function is not understood. Voxel-based morphometry is a well-established technique for localization and quantification of cerebral grey matter on the basis of MR images. This method has been used previously for interhemispheric comparison, but without examining the functional implications of the identified anatomical asymmetries of the visual system. The aim of the present study was to relate anatomical interhemispheric asymmetries to asymmetries of visual function. We examined grey matter asymmetries of visual areas in a large population (n=56) of ophthalmologically and neurologically healthy individuals. We used state-of-the-art 3 T MRI and voxel-based morphometry to relate the visual parameters, (a) ocular dominance, (b) interocular difference in visual acuity and (c) visual attention (i.e. deviation on a line-bisection task), to interhemispheric differences in grey matter volume. As most visual input from one eye is processed in the contralateral hemisphere, ocular features may also depend on cerebral lateralization. Several lateralized visual areas were identified, both right>left and left>right. When correlating the asymmetries to the functional parameters, we found a significant correlation to ocular dominance (P<0.05), whereas visual acuity and visual attention showed no such relationship. The lateral occipital complex was identified to be significantly larger in the left hemisphere for right-eyed participants and vice versa. These results suggest a cerebral basis for ocular dominance.

Comparison of the Wave Amplitude of Visually Evoked Potential in Amblyopic Eyes between Patients with Esotropia and Anisometropia and a Normal Group

BACKGROUND

We compared the wave amplitude of visually evoked potential (VEP) between patients with esotropic and anisometropic amblyopic eyes and a normal group.

METHODS

The wave amplitude of VEP was documented in 2 groups of persons with amblyopia (15 with esotropia and 28 with anisometropia) and 1 group of individuals with normal visual acuity (n, 15). The amplitude of P100 was recorded monocularly with different spatial frequencies.

RESULTS

Our statistical analysis revealed that the wave amplitude in the 2 groups with amblyopia was significantly decreased compared to that in the normal group (P<0.001). There was a significant difference regarding the amplitude in high spatial frequencies in both high- and low-contrast conditions between the groups with esotropia and anisometropia and the normal group (P<0.001). There were also significant differences in large check-size stimuli and low-contrast condition between the amblyopic groups with esotropia and anisometropia and the normal group (P=0.013 and P=0.044, respectively). In large check-size stimuli and high-contrast condition, a significant difference was indicated only in the comparison between the esotropic amblyopic eyes and the normal eyes (P=0.036).

CONCLUSION

The wave amplitude parameter of VEP was influenced by both types of amblyopia, but it seems that this parameter was more sensitive to esotropic amblyopia than anisometropic amblyopia. This outcome may reflect a non-parallel pattern of cortical responses in the comparison of the 2 types of amblyopia with each other and with the control group, which may be beneficial for the diagnosis and treatment of amblyopia.

Association of Optic Radiation Integrity with Cortical Thickness in Children with Anisometropic Amblyopia

Previous studies have indicated regional abnormalities of both gray and white matter in amblyopia. However, alterations of cortical thickness associated with changes in white matter integrity have rarely been reported. In this study, structural magnetic resonance imaging and diffusion tensor imaging (DTI) data were obtained from 15 children with anisometropic amblyopia and 15 age- and gender-matched children with normal sight. Combining DTI and surface-based morphometry, we examined a potential linkage between disrupted white matter integrity and altered cortical thickness. The fractional anisotropy (FA) values in the optic radiations (ORs) of children with anisometropic amblyopia were lower than in controls (P < 0.05). The cortical thickness in amblyopic children was lower than controls in the following subregions: lingual cortex, lateral occipitotemporal gyrus, cuneus, occipital lobe, inferior parietal lobe, and temporal lobe (P < 0.05, corrected), but was higher in the calcarine gyrus (P < 0.05, corrected). Node-by-node correlation analysis of changes in cortical thickness revealed a significant association between a lower FA value in the OR and diminished cortical thickness in the following subregions: medial lingual cortex, lateral occipitotemporal gyrus, lateral, superior, and medial occipital cortex, and lunate cortex. We also found a relationship between changes of cortical thickness and white matter OR integrity in amblyopia. These findings indicate that developmental changes occur simultaneously in the OR and visual cortex in amblyopia, and provide key information on complex damage of brain networks in anisometropic amblyopia. Our results also support the hypothesis that the pathogenesis of anisometropic amblyopia is neurodevelopmental.

P100 Wave Latency in Anisometropic and Esotropic Amblyopia versus Normal Eyes

Purpose:

To evaluate cortical activity using pattern visual evoked potentials (PVEPs) in patients with mild and moderate amblyopia (esotropic and anisometropic).

Methods:

PVEP was recorded in 43 unilateral amblyopic patients, including 15 esotropic (ET) and 28 anisometropic (AM) patients, selected from three different medical centers in the city of Shiraz, Iran and compared to that obtained from 15 age and sex matched normal subjects who served as controls. Visual acuity (VA) in amblyopic eyes was equal to or less than 0.7 LogMAR. The latency of P100 was recorded monocularly using two check sizes of 15 and 60 min of arcs at two different levels of contrasts (30% and 100%).

Results:

P100 latency in amblyopic eyes was significantly increased compared to the normal group (P < 0.001). There was a significant difference (P < 0.001) in P100 latency in anisometropic and esotropic amblyopic eyes as compared to normal subjects, using high spatial frequency and with both levels of contrast. A significant difference was observed with large check sizes and high contrast between anisometropic amblyopic and normal eyes (P = 0.03). However, there was no significant difference between these two groups and the control group with other stimuli.

Conclusion:

The neural response based on p100 latency in PVEP was different between amblyopic groups and normal subjects. PVEP may be valuable for diagnosis, prognosis and treatment of amblyopia.

BOLD fMRI and DTI in strabismic amblyopes following occlusion therapy

Evaluation of brain cluster activation using the functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) was sought in strabismic amblyopes. In this hospital-based case-control cross-sectional study, fMRI and DTI were conducted in strabismic amblyopes before initiation of any therapy and after visual recovery following the administration of occlusion therapy. FMRI was performed in 10 strabismic amblyopic subjects (baseline group) and in 5 left strabismic amblyopic children post-occlusion therapy after two-line visual improvement. Ten age-matched healthy children with right ocular dominance formed control group. Structural and functional MRI was carried out on 1.5T MR scanner. The visual task consisted of 8 Hz flickering checkerboard with red dot and occasional green dot. Blood-oxygen-level-dependent (BOLD) fMRI was analyzed using statistical parametric mapping and DTI on NordicIce (NordicNeuroLab) softwares. Reduced occipital activation was elicited when viewing with the amblyopic eye in amblyopes. An 'ipsilateral to viewing eye' pattern of calcarine BOLD activation was observed in controls and left amblyopes. Activation of cortical areas associated with visual processing differed in relation to the viewing eye. Following visual recovery on occlusion therapy, enhanced activity in bilateral hemispheres in striate as well as extrastriate regions when viewing with either eye was seen. Improvement in visual acuity following occlusion therapy correlates with hemodynamic activity in amblyopes.

Distinct patterns of spontaneous brain activity between children and adults with anisometropic amblyopia: a resting-state fMRI study

PURPOSE

To detect the altered spontaneous brain activity patterns in children and adults with anisometropic amblyopia using resting-state functional magnetic resonance imaging (rs-fMRI) technique combined with the amplitude of low-frequency fluctuation (ALFF) method.

METHODS

Thirty-two monocular anisometropic amblyopia and 34 normal-sight controls were divided into child group and adult group. Rs-fMRI was performed in all participants and analysis of ALFF value within the whole brain was conducted in each subject. ALFF value differences between the patients and controls in the two groups were compared via an independent two-sample t test.

RESULTS

The amblyopic children mainly exhibited increased ALFF in part of the bilateral calcarine (BA17), the left middle occipital gyrus (BA18/19), and the left postcentral gyrus (BA2). By contrast, the amblyopic adults showed decreased ALFF in the bilateral precuneus cortex (part of BA7), and the standardized ALFF value of bilateral precuneus were correlated with the amount of anisometropia of the amblyopic adults.

CONCLUSIONS

Rs-fMRI is an effective noninvasive technique for exploring brain activity of the anisometropic amblyopia. Our findings demonstrated that brain activity changed both in amblyopic children and adults under the resting state, and revealed the differences in spontaneous activity patterns between the amblyopic children and adults.

Amblyopia treatment strategies and new drug therapies

Amblyopia is a unilateral or bilateral reduction of visual acuity secondary to abnormal visual experience during early childhood. It is one of the most common causes of vision loss and monocular blindness and is commonly associated with strabismus, anisometropia, and visual deprivation (in particular congenital cataract and ptosis). It is clinically defined as a two-line difference of best-corrected visual acuity between the eyes. The purpose of this study was to understand the neural mechanisms of amblyopia and summarize the current therapeutic strategies. In particular, the authors focused on the concept of brain plasticity and its implication for new treatment strategies for children and adults with amblyopia.

One Year of Pediatric Ophthalmology and Strabismus Research in Review

PURPOSE

To highlight recent advances in amblyopia and strabismus.

DESIGN

Literature review.

METHODS

A literature search of articles published in the English language was performed in PubMed or MEDLINE between May 2012 and April 2013 using the terms amblyopia or strabismus. Articles deemed relevant were selected.

RESULTS

The review highlights articles that increase our understanding of strabismus and amblyopia as well as newer treatment strategies.

CONCLUSIONS

The review highlights some new information and possible future advances in amblyopia and strabismus.

Perceptual learning treatment in patients with anisometropic amblyopia: a neuroimaging study

AIMS

To investigate the neuromechanisms of perceptual learning treatment in patients with anisometropic amblyopia using functional MRI (fMRI) and diffusion tensor imaging (DTI) techniques.

METHODS

20 patients with monocular anisometropic amblyopia participated in the study. Both fMRI and DTI data were acquired for each patient twice: before and after 30 days' perceptual learning treatment for the amblyopic eye. During fMRI scanning, patients viewed the stimuli with either the sound or amblyopic eye. Changes of cortical activation after treatment were evaluated. In the DTI exams, the fractional anisotropy (FA) values, apparent diffusion coefficient (ADC) values, the voxel numbers of optic radiations (ORs), and the number of tracks were compared between the ipsilateral and the contralateral ORs and also between the previous and posterior scans.

RESULTS

Remarkable increased activation via the amblyopic eyes was found in Brodmann Area (BA) 17-19, bilateral temporal lobes, and right cingulate gyrus after the perceptual learning treatment. No significant changes were found in the FA values, ADC values, voxel numbers, and the number of tracks after the treatment.

CONCLUSIONS

These results indicate that perceptual learning treatment for amblyopia had a positive effect on the visual cortex and temporal lobe visual areas in patients with anisometropic amblyopia.

BOLD responses to different temporospatial frequency stimuli in V1 and V2 visual cortex of anisometropic amblyopia

PURPOSE

Functional magnetic resonance imaging (fMRI) is the most advanced neuroimaging technique. The aim of this study was to investigate the blood oxygenation level-dependent (BOLD) of V1 and V2 visual cortex in anisometropic amblyopia with fMRI and explore the neural mechanism of amblyopia.

METHODS

fMRI was performed with a 3.0-T MRI scanner during reversal checkerboard visual stimulation with different spatial frequencies (SF) of 0.4, 2, and 8 cpd in 2 states of temporal frequencies (TF) of 6 Hz and 8 Hz in a group of patients with anisometropic amblyopia (n=5) and a group of normal observers (n=4). Data were processed by SPM software offline. Responses of different eyes were compared in different conditions.

RESULTS

The BOLD signal magnitude in V1 and V2 visual cortex of amblyopic eyes was significantly lower than the fellow eyes with anisometropic amblyopia at low SF (0.4-2 cpd) (p<0.05), but it was significantly higher than the fellow eyes at high SF (8 cpd) (p<0.05). The BOLD signal magnitude in V1 and V2 visual cortex of amblyopic eyes was significantly lower than the nondominant eyes in normal subjects in all conditions (p<0.001).

CONCLUSIONS

There are cortical deficits in V1 and V2 visual cortex of anisometropic amblyopia, which may be useful for selecting an optimum stimulus at proper temporospatial frequency.