Kevin C. Chan1,2, Joe S. Cheng1,2,
Shu Juan Fan1,2, Matthew M. Cheung1,2, Ed X. Wu1,2
1Laboratory of Biomedical
Imaging & Signal Processing, the University of Hong Kong, Pokfulam, Hong
Kong, China, People's Republic of; 2Department of Electrical &
Electronic Engineering, the University of Hong Kong, Pokfulam, Hong Kong,
China, People's Republic of
This study examines in vivo the effect of 4 types of early postnatal visual impairments [binocular enucleation (BE), monocular enucleation (ME), monocular deprivation (MD), and dark-rearing (DR)] on the development and plasticity of the rat visual pathways using diffusion tensor imaging. Compared to age-matched control rats at 6 weeks old, results indicated a significantly lower fractional anisotropy (FA) in the visual pathways projected from both eyes in the BE rats, and from the enucleated right eye in the ME rats. A small but significantly lower FA could also be observed in the left posterior optic tract of MD rats monocularly deprived in the right eye, whereby a significantly higher FA was found in the left prechiasmatic optic nerve in the monocularly enucleated rats. No apparent difference was observed in DR rats along either visual pathway. The results of this study documented in vivo the varying degrees of microstructural alterations along the visual pathways in the 4 rat models. Future DTI studies are envisioned that measure the development and reorganization of the impaired visual pathways after early interventions in longitudinal studies.