Original article
Underdevelopment of Optic Radiation in Children With Amblyopia: A Tractography Study

https://doi.org/10.1016/j.ajo.2006.12.009Get rights and content

Purpose

To detect the abnormalities of the optic radiation (OR) in children with amblyopia by diffusion tensor imaging (DTI) and tractography.

Design

Prospective, nonrandomized clinical trial.

Methods

Fourteen children with amblyopia and 14 normally sighted children underwent DTI scanning. After the ORs were reconstructed by using tractography algorithm, voxels through which the anterior parts of ORs passed were determined for their values of fractional anisotropy (FA). The paired t test was applied to compare their mean FA values of right OR and left OR in the control group. For the amblyopia group, analysis of variance was conducted to determine the effect of laterality and vision status on the FA values. In addition, the voxel numbers of anterior and posterior parts of both ORs were calculated. The Student t test was used to compare the average FA of bilateral ORs and voxel numbers between the two groups.

Results

Comparison demonstrated left-higher-than-right asymmetry in both amblyopic children and normal children. We found no significant difference of average FA between the amblyopic group (0.4832 ± 0.0225) and control group (0.4770 ± 0.0273). Voxel numbers of the anterior parts of both ORs were not significantly different between the two groups, whereas voxel numbers of their posterior parts in the controls were more than that of amblyopic children.

Conclusion

Tractography showed more voxels in the posterior ORs of normal children than in the amblyopic children, indicating that normal children have better development of the ORs. The underdevelopment of the ORs might reflect the dysfunction of visual cortex in children with amblyopia.

Section snippets

Subjects

Fourteen pediatric patients with amblyopia (six males, eight females; age range, 4 to 8 years; mean age 5.8 years) and 14 normally sighted children (10 males, four females; age range, 3.5 to 9 years; mean age 5.8 years) were recruited in this study. Informed consent for participation was obtained from every subject’s parents and the ethics committee at Beijing University approved all the protocols used in this study. The amblyopic children were recruited by physician referral from the pediatric

Results

There was no statistical difference in age between the two groups (5.8 years ± 1.4 for children with amblyopia, 5.8 years ± 1.9 for controls).

Significant difference of FA values was detected between the two sides of ORs in the controls (t = 4.16, P = .001). In the amblyopia group, the effect of vision status and vision-by-side interaction effect were not evident along the ORs, whereas the side difference was significant (F = 6.33, P = .02). It showed that left OR had greater FA than right OR in

Discussion

Diffusion tensor imaging has been considered as a useful method in the evaluation of brain development. It is believed that FA can provide microstructural information on white matter development.10 Tractography, a technique based on DTI, allows us to extract the trajectories of certain fiber tracts in vivo. Although tractography may be affected by image resolution and signal-to-noise ratio, it frequently generates results that are reasonable and reproducible.12 Tractography of the ORs has been

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