Voxel-based Morphometric Study On The Brain In Anisometropic Amblyopia Patients

Objective:To investigate the differences of grey matter and white matter between anisometropic amblyopia patients and normal healthy volunteers by using voxel-based morphometry, and to study the possible neural mechanism of anisometropic amblyopia based on the changes of brain structures.Subjects and Methods:Thirteen anisometropic amblyopia patients were selected according to the following standards:corrected visual activity of amblyopic eye was no more than 0.3, another eye was more than 1.0. Sixteen normal subjects matched with patients in age and sexual were recruited as control in this study. Informed content was obtained from all subjects. GE 1.5T Twin speed MR Scanner was used to obtain 3-dimensional (3D) T1 images. The 3-dimensional (3D) T1 images data were processed with the software of SPM5 and VBM5.1. Preprocess included spatial normalization, segmentation of gray and white matter, and smooth. Inter-group analysis was performed with two sample t-test. Statistical parameter mapping was overlapped onto standard children brain template to observe the MNI coordinate of the brain regions with significant difference beteen two groups. The voxels and significant intensity (T value) were recorded.Results:Twelve subjects were recruited in each group according to the affected factors (head motion, behavioral performance and machine noise) were ruled out. Patients group:7 male,5 female; age range 6-13 years, mean age 9.8 years. Normal group:7 male,5 female; age range 6-13 years, mean age 10.4 years. There was not significant difference between two groups in age (t=0.998, p>0.05)Compared to healthy controls, the grey matter presented with significantly decreased density in anisometropic amblyopic patients included right cuneus, bilateral occipital gyri, right middle frontal gyrus, left middle temporal gyrus, right superior temporal gyrus, right precuneus, and middle part of right cingulate gyrus. The grey matter showed increased density included right cerebellum, right parahippocampal gyrus, left precentral gyrus, and left superior frontal gyrus. Comparison between anisometropic amblyopia patients and normal volunteers showed the white matter density in bilateral optic radiation and internal capsule, especially right optic radiation, decreased in patients group. There was not white matter showed increased density in the anisometropic amblyopic group compared with normal group.Conclusion:There is lower density in the primary visual cortex, related advanced visual cortex and white matter fibers of the posterior visual pathways in anisometropic amblyopia patients. These abnormal changes in brain structure may be the neural basis of decreased visual acuity and stereoscopic vision loss. These brain changes may occur with anisometropic amblyopia development.In anisometropic amblyopia patients, the density of gray matter in the right cerebellum, right parahippocampal gyrus, left medial frontal gyrus and left superior frontal gyrus increased. This may be related to the compensation of visual function or related to the emotional disorders in the process of long-term vision loss.