Comparison between anisometropic and strabismic amblyopia using functional magnetic resonance imaging

M Y Choi, K M Lee, J M Hwang, D G Choi, D S Lee, K H Park, Y S Yu, M Y Choi, K M Lee, J M Hwang, D G Choi, D S Lee, K H Park, Y S Yu

Abstract

Aims: To assess calcarine activation with functional magnetic resonance imaging (fMRI) in patients with anisometropic and strabismic amblyopia.

Methods: 14 amblyopes (eight anisometropic and six strabismic) were studied with fMRI using stimuli of checkerboards of various checker sizes and temporal frequencies. While T2* weighted MRI were obtained every 3 seconds for 6 minutes, patients viewed the stimuli monocularly with either the amblyopic or sound eye.

Results: Amblyopic eyes showed reduced calcarine activation compared with contralateral sound eyes in fMRI in all subjects. The calcarine activation from amblyopic eyes in anisometropic amblyopes was more suppressed at higher spatial frequencies, while that from amblyopic eyes in strabismic amblyopes was more suppressed at lower spatial frequencies.

Conclusion: These results suggest that fMRI is a useful tool for the study of amblyopia in humans. The calcarine activation via amblyopic eyes because of anisometropia or strabismus has different temporospatial characteristics, which suggests differences in the neurophysiological mechanisms between two types of amblyopia.

Figures

Figure 1
Figure 1
Examples of calcarine activation are shown for an anisometropic patient (upper) and a strabismic patient (lower), in which the activation by amblyopic eyes was found to be significantly less than that for the sound eyes. Images are vertically aligned along the calcarine fissures with occipital lobes. During visual stimulation, local increases in signal intensity were detected in the medial-posterior regions of the occipital lobes along the calcarine fissures. Yellow coloured regions represent a more activated state than the red coloured regions.
Figure 2
Figure 2
The average percentage change of functional MRI signal in anisometropic and strabismic amblyopias. Solid circles represent the sound eyes, open circles show the defocused response in sound eyes, and rectangles represent amblyopic eyes. Asterisks mean that the difference between the two responses was statistically significant (p

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