Objective To elucidate the different neuromechanisms of strabismic and anisometropic amblyopia compared with normal vision subjects using the technique of blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD-fMRI) and pattern-reversal visual evoked potential (PR-VEP).
Methods Fifty-three subjects, age range of 7-12 years, diagnosed with strabismic amblyopia (17 cases), anisometropic amblyopia (20 cases), and normal vision (16 cases), were examined using the BOLD-fMRI and PR-VEP of UTAS-E3000 techniques. Cortical activation by binocular viewing of reversal checkerboard patterns was examined in terms of the ROI-based and spatial-frequency-dependent analysis. The pertinence of cortical activation in fMRI and the amplitude of P100 inVEP were analyzed using the SPSS 12.0 software package.
Results In the procedure of BOLD-fMRI, reduced areas and decreased activation levels were found in V1 and other extrastriate areas in amblyopes compared with normal vision group. The reduced areas mainly resided in the striate visual cortex in anisometropic amblyopes. In strabismic amblyopes, a more significant cortical impairment was found in bilateral V2 and V3 than that in anisometropic amblyopes. The activation by high-spatial-frequency stimuli was reduced in bilateral BA 18 and 19 as well as BA17 inanisometropic amblyopes, whereas it was only reduced in BA 18 and19 instrabismic amblyopes. These findings were further confirmed by the ROI-based analysis. During spatial-frequency-dependent VEP detection, anisometropic amblyopes were sensitive to high spatial frequency, but that was not found in strabismic amblyopes. The cortical activation in fMRI with the ROI-based analysis was significantly correlated with the amplitude of P100 inVEP recording.
Conclusion Combined spatial-frequency-dependent BOLD-fMRI with PR-VEP could differentiate among various kinds of amblyopia according to their different cortical responses. The neuromechanism was different in strabismic amblyopia and anisometropic amblyopia. |
