Treating amblyopia using altered reality enhances the fine-scale functional correlations in early visual areas.

Amblyopia is a developmental visual disorder that causes substantial visual deficits. Studies using resting-state functional magnetic resonance imaging have disclosed abnormal brain functional connectivity (FC) both across long-range cortical sites and within the visual cortex in amblyopes, which is considered to be related to impaired visual functions. However, little work has examined whether restoring the vision of amblyopes accompanies with an improvement of FC. Here in adult amblyopes and healthy participants, we compared their brain FC before and after an altered-reality adaptation training. Before the training, the voxel-wise FCs of amblyopia patients were substantially weaker than those of healthy control participants both within and across the early visual areas. After the training, visual acuities improved in amblyopes but not in the control participants. The effect kept strengthening in the subsequent month without further adaptation. Importantly, we observed enhanced voxel-wise FC both within and across the early visual areas of amblyopes. Moreover, the enhancement continued for at least 1 month. These results suggest that the effective treatment can improve both the amblyopes' vision and functional connections in the visual cortex.

Altered local spontaneous brain activity pattern in children with right-eye amblyopia of varying degrees: evidence from fMRI.

PURPOSE: To investigate the abnormal changes of local brain activity in children with right-eye amblyopia of varying degrees. METHODS: Data of resting-state functional magnetic resonance imaging were collected from 16 children with severe amblyopia, 17 children with mild to moderate amblyopia, and 15 children with normal binocular vision. Local brain activity was analyzed using the amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo). RESULTS: There were extensive ALFF differences among the three groups in 10 brain regions. There were extensive differences in ReHo among the three groups in 11 brain regions. The ALFF and ReHo of the right orbital part of the middle frontal gyrus displayed a significantly positive correlation with the best-corrected visual acuity of the right eye, respectively. The ALFF value and ReHo value of the right orbital part of the middle frontal gyrus followed the pattern of normal control < mild to moderate amblyopia < severe amblyopia. CONCLUSION: This study demonstrated that there were changes in specific patterns of ALFF and ReHo in children with right-eye amblyopia of different degrees in brain regions performing visual sensorimotor and attentional control functions.

Excitatory Contribution to Binocular Interactions in Human Visual Cortex Is Reduced in Strabismic Amblyopia.

Binocular summation in strabismic amblyopia is typically reported as being absent or greatly reduced in behavioral studies and is thought to be because of a preferential loss of excitatory interactions between the eyes. Here, we studied how excitatory and suppressive interactions contribute to binocular contrast interactions along the visual cortical hierarchy of humans with strabismic and anisometropic amblyopia in both sexes, using source-imaged steady-state visual evoked potentials (SSVEP) over a wide range of relative contrast between the two eyes. Dichoptic parallel grating stimuli modulated at unique temporal frequencies in each eye allowed us to quantify spectral response components associated with monocular inputs (self-terms) and the response components because of interaction of the inputs of the two eyes [intermodulation (IM) terms]. Although anisometropic amblyopes revealed a similar pattern of responses to normal-vision observers, strabismic amblyopes exhibited substantially reduced IM responses across cortical regions of interest (V1, V3a, hV4, hMT+ and lateral occipital cortex), indicating reduced interocular interactions in visual cortex. A contrast gain control model that simultaneously fits self- and IM-term responses within each cortical area revealed different patterns of binocular interactions between individuals with normal and disrupted binocularity. Our model fits show that in strabismic amblyopia, the excitatory contribution to binocular interactions is significantly reduced in both V1 and extra-striate cortex, whereas suppressive contributions remain intact. Our results provide robust electrophysiological evidence supporting the view that disruption of binocular interactions in strabismus or amblyopia is because of preferential loss of excitatory interactions between the eyes.SIGNIFICANCE STATEMENT We studied how excitatory and suppressive interactions contribute to binocular contrast interactions along the visual cortical hierarchy of humans with normal and amblyopic vision, using source-imaged SSVEP and frequency-domain analysis of dichoptic stimuli over a wide range of relative contrast between the two eyes. A dichoptic contrast gain control model was used to characterize these interactions in amblyopia and provided a quantitative comparison to normal vision. Our model fits revealed different patterns of binocular interactions between normal and amblyopic vision. Strabismic amblyopia significantly reduced excitatory contributions to binocular interactions, whereas suppressive contributions remained intact. Our results provide robust evidence supporting the view that the preferential loss of excitatory interactions disrupts binocular interactions in strabismic amblyopia.

Single Center to Evaluate and Compare Anisometropic Amblyopia in Adults Using Blood Oxygenation Level-Dependent Functional Magnetic Resonance Imaging and Diffusion Kurtosis Imaging.

BACKGROUND Anisometropic amblyopia results from the unequal ability to focus between the right and left eyes. Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) measures the proportion of oxygenated hemoglobin in specific areas. Diffusion kurtosis imaging (DKI) is a method of diffusion tensor imaging that estimates the skewed distribution of water diffusion probability. We aimed to evaluate and compare 11 adult patients with anisometropic amblyopia (AA) with 13 normally sighted healthy controls (HC) using BOLD-fMRI and DKI. MATERIAL AND METHODS Eleven adults with AA (age range 20-49; mean age 29.18±8.089) and 13 HC adults (age range 22-50; mean age 28.00±5.79) were recruited. DKI scanning used a single excitation echo-planar imaging sequence and a region of interest to obtain DKI parameters for optic radiation; the corpus callosum was manually placed, including mean kurtosis (MK), fractional anisotropic (FA), and mean diffusivity (MD) values; and BOLD data used a gradient-echo echo-planar imaging sequence. RESULTS The AA group had lower MK and FA of bilateral optic radiation than the HC group (P=0.008 and P=0.006, respectively) and higher MD than the HC group (P=0.005). The MK of the corpus callosum in the AA group was lower than that of HC group (P=0.012).Compared with the non-dominant eyes of the HC group, the amblyopic eyes in the AA group had less activation range and intensity in Brodmann areas 17, 18, and 19. CONCLUSIONS The combined use of DKI and BOLD-fMRI detected microstructural changes associated with local visual pathways and identified damage to the visual cortex in patients with amblyopia.

Functional connectivity density alterations in children with strabismus and amblyopia based on resting-state functional magnetic resonance imaging (fMRI).

PURPOSE: To explore functional connectivity density (FCD) values of brain areas in children with strabismus and amblyopia (SA) based on blood oxygen level-dependent (BOLD) signals. METHODS: This study recruited 26 children (14 male, 12 females) with SA and 26 healthy children (14 male, 12 female) as healthy controls (HCs). Both groups matched in age, gender, educational level and socioeconomic background. While resting, all participants underwent fMRI scanning and global FCD (gFCD) and local FCD (lFCD) values were calculated. Receiver operating characteristic (ROC) curves were created to investigate whether there was a significant difference between children with SA and healthy controls. RESULTS: When compared with healthy controls, children with SA had significantly lower gFCD values in the right cerebellum, left putamen, and right superior frontal gyrus; however, the same metrics showed opposite changes in the right angular gyrus, left middle cingulate gyrus, left angular gyrus, right superior parietal gyrus, and right middle frontal gyrus. In children with SA, lFCD values were found to be remarkably decreased in regions of the middle right temporal pole, right cerebellum, left putamen, left hippocampus, right hippocampus, left thalamus, left cerebellum; values were increased in the right superior parietal gyrus as compared with healthy controls. CONCLUSION: We noted abnormal neural connectivity in some brain areas of children with SA; detailing such connectivity aberrations is useful in exploring the pathophysiology of SA and providing useful information for future clinical management.

Altered functional connectivity of primary visual cortex in adults with strabismus and amblyopia: a resting-state fMRI study.

Functional connectivity of the primary visual cortex was explored with resting functional magnetic resonance imaging among adults with strabismus and amblyopia and healthy controls. We used the two-sample test and receiver operating characteristic curves to investigate the differences in mean functional connectivity values between the groups with strabismus and amblyopia and healthy controls. Compared with healthy controls, functional connectivity values in the left Brodmann areas 17, including bilateral lingual/angular gyri, were reduced in groups with strabismus and amblyopia. Moreover, functional connectivity values in the right Brodmann area 17, including left cuneus, right inferior occipital gyrus, and left inferior parietal lobule, were reduced in adults with strabismus and amblyopia. Our findings indicate that functional connectivity abnormalities exist between the primary visual cortex and other regions. This may be the basis of the pathological mechanism of visual dysfunction and stereovision disorders in adults with strabismus and amblyopia.

[Abnormal spontaneous brain functional activity in adult patients with amblyopia: a resting-state functional magnetic resonance imaging study].

Amblyopia is a visual development deficit caused by abnormal visual experience in early life, mainly manifesting as defected visual acuity and binocular visual impairment, which is considered to reflect abnormal development of the brain rather than organic lesions of the eye. Previous studies have reported abnormal spontaneous brain activity in patients with amblyopia. However, the location of abnormal spontaneous activity in patients with amblyopia and the association between abnormal brain function activity and clinical deficits remain unclear. The purpose of this study is to analyze spontaneous brain functional activity abnormalities in patients with amblyopia and their associations with clinical defects using resting-state functional magnetic resonance imaging (fMRI) data. In this study, 31 patients with amblyopia and 31 healthy controls were enrolled for resting-state fMRI scanning. The results showed that spontaneous activity in the right angular gyrus, left posterior cerebellum, and left cingulate gyrus were significantly lower in patients with amblyopia than in controls, and spontaneous activity in the right middle temporal gyrus was significantly higher in patients with amblyopia. In addition, the spontaneous activity of the left cerebellum in patients with amblyopia was negatively associated with the best-corrected visual acuity of the amblyopic eye, and the spontaneous activity of the right middle temporal gyrus was positively associated with the stereoacuity. This study found that adult patients with amblyopia showed abnormal spontaneous activity in the angular gyrus, cerebellum, middle temporal gyrus, and cingulate gyrus. Furthermore, the functional abnormalities in the cerebellum and middle temporal gyrus may be associated with visual acuity defects and stereopsis deficiency in patients with amblyopia. These findings help explain the neural mechanism of amblyopia, thus promoting the improvement of the treatment strategy for amblyopia.

Neural markers of suppression in impaired binocular vision.

Even after conventional patching treatment, individuals with a history of amblyopia typically lack good stereo vision. This is often attributed to atypical suppression between the eyes, yet the specific mechanism is still unclear. Guided by computational models of binocular vision, we tested explicit predictions about how neural responses to contrast might differ in individuals with impaired binocular vision. Participants with a history of amblyopia (N = 25), and control participants with typical visual development (N = 19) took part in the study. Neural responses to different combinations of contrast in the left and right eyes, were measured using both electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). Stimuli were sinusoidal gratings with a spatial frequency of 3c/deg, flickering at 4 Hz. In the fMRI experiment, we also ran population receptive field and retinotopic mapping sequences, and a phase-encoded localiser stimulus, to identify voxels in primary visual cortex (V1) sensitive to the main stimulus. Neural responses in both modalities increased monotonically with stimulus contrast. When measured with EEG, responses were attenuated in the weaker eye, consistent with a fixed tonic suppression of that eye. When measured with fMRI, a low contrast stimulus in the weaker eye substantially reduced the response to a high contrast stimulus in the stronger eye. This effect was stronger than when the stimulus-eye pairings were reversed, consistent with unbalanced dynamic suppression between the eyes. Measuring neural responses using different methods leads to different conclusions about visual differences in individuals with impaired binocular vision. Both of the atypical suppression effects may relate to binocular perceptual deficits, e.g. in stereopsis, and we anticipate that these measures could be informative for monitoring the progress of treatments aimed at recovering binocular vision.

Altered Brain Network Centrality in Patients with Adult Strabismus with Amblyopia: A Resting-State Functional Magnetic Resonance Imaging (fMRI) Study.

BACKGROUND The aim of this study was to explore potential changes in brain function network activity in patients with adult strabismus with amblyopia (SA) using the voxel-wise degree centrality (DC) method. MATERIAL AND METHODS We enrolled 15 patients with SA (6 males, 9 females) and 15 sex-matched healthy controls (HCs). All subjects completed resting functional magnetic resonance imaging scans. Independent-sample t tests and receiver operating characteristic (ROC) curves were used to assess DC value differences between groups, and Pearson correlation analysis was performed to evaluate correlations between DC-changed brain regions and clinical data of patients with SA. RESULTS Compared with the HC group, DC values that were lower in patients with SA included the left middle frontal gyrus and bilateral angular gyri. Increases were observed in the left fusiform gyrus, right lingual gyrus, right middle occipital gyrus, right postcentral gyrus, and left paracentral lobule. However, DC values were not correlated with clinical manifestations. ROC curve analysis showed high accuracy. CONCLUSIONS We found abnormal neural activity in specific brain regions in patients with SA. Specifically, we observed significant changes in DC values compared to HCs. These changes may be useful to identify the specific mechanisms involved in brain dysfunction in SA.

Quantitative analysis of macular and peripapillary microvasculature in adults with anisometropic amblyopia.

INTRODUCTION: The aim of this study was to compare the macular and peripapillary capillary vessel density (CVD) and foveal avascular zone (FAZ) in amblyopic eyes of adults with their fellow eyes and with eyes of healthy controls using optical coherence tomography-angiography (OCT-A). METHODS: A total of 34 eyes of 17 patients with anisometropic amblyopia and 80 eyes of 40 age- and gender-matched healthy controls were included. CVD in superficial (SCP) and deep retinal capillary plexuses (DCP), peripapillary region, and FAZ were analyzed by OCT-A. RESULTS: The median ages were 31 years (range 20-64) in patients with amblyopia and 34.5 years (range 24-65) in healthy controls (p = 0.242). The mean FAZ area measured was 0.329 ± 0.024 mm2 in amblyopic eyes, 0.332 ± 0.025 mm2 in fellow eyes, and 0.269 ± 0.015 mm2 in control eyes (p < 0.05). The amblyopic eye of participants showed a decrease in CVD of SCP and DCP (p < 0.001, for all). The inside optic disk CVD measurements were lower in the amblyopic eyes than in the fellow eyes (p = 0.001) and healthy subjects (p = 0.015). CONCLUSION: Significant differences in macular and peripapillary microvasculature were found in anisometropic amblyopic patients. The clinical significance of the results requires further investigation.

Two cortical deficits underlie amblyopia: A multifocal fMRI analysis.

Amblyopia is a relatively common (incidence 3%) developmental disorder in which there is loss of vision as a consequence of a disruption to normal visual development. Although the deficit is monocular and known to be of cortical origin, the nature of the processing deficit is controversial. Human behavioral studies have identified two main deficits - a loss of contrast sensitivity and perceived spatial distortions. Here we use a multifocal fMRI approach to ascertain, in a group of anisometropic amblyopes, whether these two deficits have a single common cause or whether they are the result of two underlying independent cortical disorders. We found that fMRI magnitudes were attenuated in amblyopic eye stimulation, and that there was poor fidelity for co-localization of the activity clusters between the amblyopic and fellow-fixing eye stimulation. These effects varied across eccentricities and correlate with the degree of amblyopia but not with one another, suggesting two independent cortical deficits: a reduced responsiveness as well as reduced fidelity of spatial representation. These deficits are independent of eccentricity within the central field and consistent across early cortical visual areas.

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.

Correlation of the measurements of optical coherence tomography and diffuse tension imaging of optic pathways in amblyopia.

The aim of this study was to investigate whether a correlation exists between optical coherence tomography (OCT) of retina and diffusion tensor imaging (DTI) of the optic pathway measurements. All subjects underwent OCT measurements of optic nerve head, retinal nerve fiber layer, and macula. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of optic pathways were analyzed using DTI. Prechiasmatic FA values were significantly decreased in unilateral amblyopic group in both affected and sound fellow eyes (p = 0.019 and 0.013), but not in bilateral amblyopic group (p = 0.221) when compared with the control group. ADC values were significantly greater in sound eye in unilateral amblyopic group in prechiasmatic and postchiasmatic regions (p = 0.001 and 0.049). ADC values were also significantly greater in bilateral amblyopic group in postchiasmatic region (p = 0.037). There were no significant differences between the affected eye and sound eye side DTI measurements. There was no significant correlation between prechiasmatic DTI and OCT measurements in affected and sound eyes of unilateral amblyopia group. DTI results demonstrated that there is a functional underdevelopment of the anterior and posterior visual pathways in both affected and sound eye of unilateral amblyopic patients. Significantly reduced FA values in prechiasmatic region where OCT values of retina were normal can be explained by possible micro-structural changes.

In vivo optical imaging of amblyopia: Digital subtraction autofluorescence and split-spectrum amplitude-decorrelation angiography.

BACKGROUND AND OBJECTIVES: Amblyopia is a visual impairment that is attributed to either abnormal binocular interactions or visual deprivation. The retina and choroids have been shown to be involved in the development of amblyopia. The purpose of this study was to investigate the retinal and choroidal microstructural abnormalities of amblyopia using digital subtraction autofluorescence and split-spectrum amplitude-decorrelation angiography (SSADA) approaches. METHODS: This prospective study included 44 eyes of 22 patients with unilateral amblyopia. All patients who received indirect ophthalmoscopy, combined depth imaging spectral domain optical coherence tomography (OCT), SSADA-OCT, and macular blue light (BL-) and near-infrared (NIR-) autofluorescences underwent pupil dilation. The subfoveal choroidal thickness (SFCT) was measured. BL- and NIR-autofluorescences were determined for all patients and used to generate subtraction images with ImageJ software. The superficial, deep layers of the retina, and inner choroid layer were required for SSADA-OCT. RESULTS: For the normal eyes, a regularly increasing signal was observed in the central macula based on the subtraction images. In contrast, a decreased signal for the central patch or a reduced peak was detected in 16 of 22 amblyopic eyes (72.7%). The mean SFCT of the amblyopic eyes was greater than that of the fellow normal eyes (399.25 ± 4.944 µm vs. 280.58 ± 6.491 µm, respectively, P < 0.05). SSADA-OCT revealed a normal choroidal capillary network in all fellow normal eyes. However, 18 of 22 amblyopic eyes (86.4%) exhibited a blurry choroidal capillary network, and 15 of 22 amblyopic eyes (68.2%) displayed a dark atrophic patch. CONCLUSIONS: This is the first report of amblyopia using SSADA-OCT and digital subtraction images of autofluorescence. The mechanistic relationship of a thicker choroid and choroidal capillary atrophy with amblyopia remains to be described. The digital subtraction image confirmed the changes in the microstructure of the amblyopic retina as a supplementary approach to detect the progression of amblyopia. Lasers Surg. Med. 48:660-667, 2016. © 2016 Wiley Periodicals, Inc.

Microvasculature evaluation of anisometropic amblyopia children by Angio-OCT.

To compare and assess the choroidal and retinal microstructural vascularity in amblyopic eyes with the fellow eyes in anisometropic amblyopic children using angiography optical coherence tomography (Angio-OCT). Twenty-seven children (54 eyes; 5.59 ± 1.08 years old; 59.3% girls) were enrolled in this study. Choroidal thickness (CT) was measured with the use of the enhanced depth imaging mode in Angio-OCT. Parafoveal/peripapillary vascular density indices and the foveal avascular zone (FAZ) size were analyzed by MATLAB code programming on Angio-OCT images. The mean FAZ size of the amblyopic eyes were larger both in superficial and deep capillary plexus layer (SCPL/DCPL). Compared with the contralateral eyes (BCVA were normal), all the vascular density indices of SCPL and DCPL in the parafoveal and peripapillary zones were lower in the amblyopic eyes, however, the difference was insignificant (p > 0.05). No significant decrease was observed in four quadrants analyses of the amblyopic eyes (p > 0.05). Except for the measurement at 2000 µm and 1500 µm from the fovea in temple, CT in amblyopic eyes were significantly thicken than the fellow eyes (p < 0.05). Compared with the fellow eyes, the CT of certain areas were thicker in the amblyopic eyes. Though the FAZ size of the amblyopic eyes was larger in SCPL/DCPL layers, the retinal vascular density indices in SCPL/DCPL were lower in amblyopia eyes without statistical difference. Angio-OCT may be an effective way to evaluate the status of the choroidal and retinal vascular system in amblyopic children.

Macular superficial vascular density on optical coherence tomography angiography in children with unilateral anisometropic and bilateral hyperopic amblyopia.

We analyzed whether macular superficial vascular density (SVD) and foveal vascular zone (FAZ) on optical coherence tomography angiography (OCTA) can distinguish between bilateral ametropic and anisometropic amblyopia. We included 42, 33, and 50 eyes in the bilateral ametropic amblyopia, anisometropic amblyopia, and normal control groups, respectively. Using macular swept-source optical coherence tomography angiography, we measured and analyzed the superficial FAZ areas and five sectoral macular SVDs after magnification correction. The anisometropic amblyopic eye group showed significantly increased foveal SVDs (p < 0.001) and significantly decreased superficial FAZ areas (p < 0.001), compared with the remaining groups. Additionally, the bilateral ametropic amblyopia group had significantly decreased nasal SVDs. SVDs and superficial FAZ areas differed among hyperopic amblyopia subtypes. These findings may reflect vascular distribution differences and macular changes in hyperopic amblyopia subtypes compared with normal eyes.

The effect of anisometropic amblyopia on retrobulbar blood flow parameters. Anisometropic amblyopia and retrobulbar blood flow.

To look for a correlation between or the effect of anisometropia amblyopia on retrobulbar blood flow parameters. Peak systolic velocity (PSV) and end-diastolic velocity (EDV) of the ophthalmic artery (OA), central retinal artery (CRA), and temporal posterior ciliary artery (tPCA) were measured with color Doppler imaging, and systolic/diastolic ratio, resistivity index (RI), and pulsatility index (PI) were computed in 42 patients with anisometropic amblyopia. The mean PSV of OA, CRA, and tPCA in amblyopic and fellow eyes were 62.69 ± 24.04, 62.64 ± 20.18; 9.28 ± 3.71, 10.27 ± 4.18; 10.81 ± 4.59, 11.28 ± 4.91, respectively. The mean EDV of OA, CRA, and tPCA in amblyopic and fellow eyes were 15.87 ± 11.31, 14.52 ± 6.54; 2.48 ± 1.17, 2.62 ± 2.06; 3.04 ± 2.34, 3.14 ± 2.18, respectively. The mean RI of OA, CRA, and tPCA in amblyopic and fellow eyes were 0.76 ± 0.08, 0.76 ± 0.08; 0.72 ± 0.08, 0.74 ± 0.95; 0.72 ± 0.09, 0.72 ± 0.08, respectively. The mean PI of OA, CRA, and tPCA in amblyopic and fellow eyes were 1.77 ± 0.42, 1.81 ± 0.46; 01.58 ± 0.42, 1.59 ± 0.43; 1.54 ± 0.43, 1.58 ± 0.49, respectively. There was no statistically significant difference in any of the measured parameters between the amblyopic and fellow eyes. Anisometropic amblyopia did not cause any change in retrobulbar blood flow in amblyopic eyes.

Optical coherence tomography angiography in amblyopia: A critical update on current understandings and future perspectives.

Optical coherence tomography angiography (OCTA) is a non-invasive tool to assess the retino-choroidal vasculature in vivo. It tracks the red blood cell movement and maps the vasculature in quick succession. In routine, diabetic retinopathy, age related macular degeneration, central serous chorioretinopathy, and others are commonly being studied to unveil its clinic role. On the other hand, amblyopia is a condition where the visual acuity is subnormal due to non-organic causes in the eye. But the OCTA studies till now have shown variable changes along retino-choroidal vasculature. Hence, to comprehend the existing literature knowledge, a systematic literature search was carried out and the original works describing novel findings in amblyopic eyes on OCTA were included. Upon detailed assessment, firstly, the disturbed vasculature along superficial retinal plexus, deeper retinal plexus, and choroidal plexus were evident in most untreated amblyopic eyes. However, such changes were not uniform, which is due to noted heterogenic patient profile, small sample size, biometric biases, non-uniform algorithms, and other factors. And to note, even in presence of such diverse changes, almost all the authors stated a plausible explanation for their notable changes. Secondly, the utility of OCTA in identifying vascular changes with standard treatments and segregation of visual beneficiaries from non-beneficiaries were possible. Hence, to conclude, OCTA is a valuable tool which can provide valuable useful insights into the amblyopic eyes during pre and post treatment periods. However, to gather more concrete evidence for clinical benefits, systematic, homogenous, and better structured clinical studies are mandated.

Measurement Of Retinal Nerve Fiber Layer Thickness In Patients Of Unilateral Amblyopia Using Optical Coherence Tomography.

BACKGROUND: The retinal changes that develop in the eyes during amblyopia are still unclear. It has been proven that thickness of the nerve fiber layer of the retina is positively correlated with refractive error. The objective of the present study was to measure the Retinal Nerve Fiber Layer Thickness (RNFLT) using Ocular Coherence Tomography (OCT) in patients of amblyopia.. METHODS: A descriptive study was conducted in the Department of LRBT Free Eye Hospital, Lahore for 6 months. After meeting the inclusion criteria, 80 patients (40 amblyopic and 40 normal) were taken and grouped as A and B. Socio-demographic details of all the patients were recorded. They then underwent a complete ophthalmologic evaluation that included BCVA, slit lamp biomicroscopy, OCT examination was carried by TOPCON OCT. Each examination was done using the "fast retinal thickness" protocol for each test eye. Mean RNFLT was calculated for each eye. RESULTS: The mean age of patients was 12.58±4.44 years. There were 20 (50%) males and 20 (50%) females. In amblyopic eyes, the mean RNFLT was 125.82±13.06mm while in normal eyes, the mean RNFLT was 94.82±1.11mm. The overall mean RNFLT was significantly higher in amblyopic eyes as compared to normal eyes (p<0.01), as well as significant when data was stratified for age and gender. CONCLUSIONS: There was significant difference observed in RNFLT in amblyopic eyes as compared to normal eyes. So, these results can help us to enhance our knowledge and understand the causes of amblyopia hence improving diagnosis and management of disease.

Abnormal effective connectivity in visual cortices underlies stereopsis defects in amblyopia.

The neural basis underlying stereopsis defects in patients with amblyopia remains unclear, which hinders the development of clinical therapy. This study aimed to investigate visual network abnormalities in patients with amblyopia and their associations with stereopsis function. Spectral dynamic causal modeling methods were employed for resting-state functional magnetic resonance imaging data to investigate the effective connectivity (EC) among 14 predefined regions of interest in the dorsal and ventral visual pathways. We adopted two independent datasets, including a cross-sectional and a longitudinal dataset. In the cross-sectional dataset, we compared group differences in EC between 31 patients with amblyopia (mean age: 26.39 years old) and 31 healthy controls (mean age: 25.71 years old) and investigated the association between EC and stereoacuity. In addition, we explored EC changes after perceptual learning in a novel longitudinal dataset including 9 patients with amblyopia (mean age: 15.78 years old). We found consistent evidence from the two datasets indicating that the aberrant EC from V2v to LO2 is crucial for the stereoscopic deficits in the patients with amblyopia: it was weaker in the patients than in the controls, showed a positive linear relationship with the stereoscopic function, and increased after perceptual learning in the patients. In addition, higher-level dorsal (V3d, V3A, and V3B) and ventral areas (LO1 and LO2) were important nodes in the network of abnormal ECs associated with stereoscopic deficits in the patients with amblyopia. Our research provides insights into the neural mechanism underlying stereopsis deficits in patients with amblyopia and provides candidate targets for focused stimulus interventions to enhance the efficacy of clinical treatment for the improvement of stereopsis deficiency.