| ObjectiveThe study was designed to detect the changes of white matter (WM) in children with anisometropic amblyopia using three different analytical methods and explore the relationship between the corrected vision and fractional anisotropic (FA) value of the abnormal areas detected in anisometropic amblyopic children. It can provide an experimental basis for the study of underlying neural mechanism in anisometropic amblyopia from the aspect of WM changes.Subjects and methods3D T1WI and DTI were obtained from twenty-three anisometropic amblyopic children and twenty-one age-matched normal subjects in this study. All subjects were right-handed and free of neurological diseases. Their parents were informed of the experiment process and signed informed consent form. Due to artifacts, some data were excluded. The subjects that met the inclusion criteria of3D structural image processing:14anisometropic amblyopia subjects(10males,4females; age from6to14years; average age10.07years) and20normal sight subjects (10males,10females; age from5to14years; average age10.85years). Degree of amblyopia is moderate/severe and visual acuity of unaffected eye≥0.9. The subjects who met the inclusion criteria of DTI image processing:20anisometropic amblyopia subjects(15males,5females; age from5to14years; average age9.6years) and18normal sight subjects (8males,10females; age range4to14years; average age10.8years). Degree of amblyopia is moderate/severe and visual acuity of unaffected eye≥0.9.The3D T1WI structural image was analyzed by voxel-based morphometry (VBM) with the software of Statistical Parameter Mapping8(SPM8) running on Matlab. For DTI analysis, we used two methods, that is, the voxel-based analytical method (FA-VBA) and the Tract-Based Spatial Statistics (TBSS) method. For the former one, FA maps were first calculated using DTI Studio software (Version2.4.01), and then the maps were spatially normalized using SPM8.For the latter one, the data were reprocessed using the FMRIB Software Library (FSL). Before combining the FA maps to generate mean FA image, DTI images were corrected for head motion and eddy current artifacts. Then, the mean FA image of all subjects was to construct a mean WM tract skeleton. Individual WM tract skeletons were transformed to the MNI space aiming to observe FA value changes in children with anisometropic amblyopia. In the end, we analyzed the correlation between mean FA values in regions of interest (ROI) and corrected visual acuity with age and gender as covariates, which were showed in the scatterplot.Results1. Results of VBM:Compared to healthy controls, anisometropic amblyopic group showed decreased WM volume in left calarine sulcus and superior parietal lobule, whereas increased WM volume was detected in right cuneus. The threshold was set at p<0.001(uncorrected) and a cluster size of≥50voxels.2. Results of VBA:Compared to the normal sighted group, reduced FA values were detected in the left lingual gyrus, the right fusiform and the right insula. Besides that, there are increased FA values in the left fusiform and left precentral area. The threshold was set at p<0.001(uncorrected) and a cluster size of≥9voxels.3. Results of TBSS:FA values of patients were significantly lower than the healthy subjects in the bilateral optic radiation, right optic chiasma, left inferior longitudinal fasciculus, right superior longitudinal fasciculus and left inferior fronto-occipital fasciculus.In addition, another three areas showed increased FA in amblyopic subjects, including the left optic radiation, corpus callosum and unciform fasciculus/fronto-occipital fasciculus.4. Results of correlation analysis:Mean FA values of bilateral optic radiation and the right superior longitudinal fasciculus showed marked positive relationship with the corrected visual acuity in children with anisometropic amblyopia.Conelusions:1.In anisometropic amblyopia, WM which related to visual and cognitive networks underwent volume loss and FA value changes. These findings suggest that there are not only morphologic defects but also microstructural changes in WM with children of anisometropic amblyopia, and the WM impairment even involved the advanced cognitive network.2. The subjects of the patient group are monocular amblyopic children. The results showed that WM that related to vision induced a compensation effect. It means that the visual pathways of the fellow eye will be in full use which promote fiber tracts development in amblyopia.3. Mean FA values of the bilateral optic radiation and right superior longitudinal fasciculus were positively correlated with the corrected visual acuity in children with anisometropic amblyopia, which indicates that the poorer an individual’s eyesight, the worse integrity, compactness and consistency of direction of WM fiber.4. The changes of WM that related to vision were observed in all three analytical methods, which make the results more believable. It will be helpful in understanding the influence on WM development in patients of anisometropic amblyopia and provides an experimental basis for the study of underlying neural mechanism in anisometropic amblyopia... |
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