Bold-functional MRI Evaluation Of The Function Of The Visual Cortex In Children Ametropic Amblyopia

Objective:To assess the influence of ametropic amblyopia on different level of visual cortex and compare the features of the cortex activations before and after ametropia correction on ametropic amblyopias with blood oxygenation dependent level functional MRI techniques (bold-fMRI).Methods:Functional evaluations were performed on a 1.5 Tesla MR (SIEMENS AVANTO) device with the experimental group before and after ametropia correction on 18 ametropic amblyopes and 18 normal subjects in control group. Blocks design mode was used. The stimulating apparatus was self-made black and white rotary grating and stationary grating is vertical. No other light was allowed in the scanning room. Choosed 18 ametropic amblyopes children on the department of ophthalmology of lanzhou general hosptial of lanzhou military command as experimental group, and 18 normal subjects as countrl group. All amblyopic children were tested naked eyes and after ametropia correction and the normal children were tested only naked eyes. The T1- weighted structure charts was collected by Turbo Spin Echo(TSE) sequence. The functional image data was acquired with a echo-planar imaging(EPI)sequence. At the end of the experiment, anatomical reference images were collected using a three-dimensional, T1-weighted MPRAGE imaging sequence. All data obtained were analyzed with the own software of the scanner. The activation areas were measured in occipital lobe. Choose the Brodmann17,18,19 area as region of Interest(ROI). To compute the total voxel of ROI as Visual cortex activation area. The SPSS 18.0 software was used for statistic analysis. The cortical activations of amblyopic children naked eyes and after ametropia correction were compared. The cortical activations of amblyopic children and the normal sight children were compared. All the amblyopic eyes were measured the visual acuity. And analyzed the correlation between the the cortical activation and the amblyopic level.Results:In the experimental group, eighteen subjects have finished the condition of the activation comparison naked eyes and after ametropia correction. Subjects in the control group have all finished experimental conditions. We found that the cortex was activated obviously in the calcarine cortex around in both the experimental group and the control group. The cortex activation area of naked eyes(9.42±4.22)was lower than after ametropia correction(10.57±4.39, t=-6.524, P=0.00, P<0.05 Paired-Samples T-test)for amblyopic eyes. To compare the different age groups, we found there are on diffenence of cortex activation area in the 4～6 years old children between the control group and the experimental group (t=0.25, P=0.981); in 7～8 and 9～years old children, the cortex activation area of experimental group are lower then the control group(t=2.23, P=0.034, t=-3.626, P=0.002). However, the activation area after ametropia correction is less than that of the normal sight eyes(14.30±2.09 t=3.248, P=0.003, P<0.05, Independent-Samples-test). we used amblyopic degree to evaluated the function lesion of cortical activation depend on the visual acuity.Conclusions:(1) There are apparent changes of cortical activity in Brodmann 17 18 19 for ametropia amblyopia. (2) Ametropia correction can increase amblyopic eye's cortex activity obviously. It is suggests that ametropia amblyope should be treated as early as possible. (3) There is no linear correlation between the function decrease of cortical activity and amblyopic degree. It implies that the amblyopic degree depend on eyesight test perhaps can't reflect the changes of the visual function for amblyopia.