Rationale and Objectives
The aims of this study was to evaluate, using 3-T diffusion tensor imaging, changes of fractional anisotropy (FA) in the orbital and intracranial part of the optic nerve (ON), the optic chiasm, the lateral geniculate nucleus, and different parts of the optic radiation (OR) in patients with glaucoma compared to controls and to determine whether FA correlates with disease severity.
Materials and Methods
Twenty patients with glaucoma and 22 age-matched controls were examined using 3-T diffusion tensor imaging. Regions of interest were positioned on the FA maps, and mean values were calculated for each ON, optic chiasm, lateral geniculate nucleus, and OR. Results were compared to those from controls and correlated with ON atrophy and reduced spatial-temporal contrast sensitivity of the retina.
Results
Compared to controls, FA in patients with glaucoma was significantly lower in the intracranial part of the ON (0.48 ± 0.15 vs 0.66 ± 0.12, P < .05) and in the OR (0.40 ± 0.16 to 0.48 ± 0.17 vs 0.53 ± 0.20 to 0.64 ± 0.11, P < .05). A high correlation between reduced FA in the intracranial ON and OR and ON atrophy and spatial-temporal contrast sensitivity of the retina was observed ( r > 0.81). Otherwise, there was no significant difference in FA between patients with glaucoma and controls measured in the orbital part of the ON, optic chiasm, and lateral geniculate nucleus.
Conclusions
Diffusion tensor imaging at 3 T allows robust FA measurements in the intracranial part of the ON and the OR. FA is significantly reduced in patients with glaucoma compared to controls, with a good correlation with established ophthalmologic examinations.
Glaucoma is responsible for approximately 10% of cases of blindness throughout the world and thus is the third leading cause of blindness, with >8 million cases each year . Glaucoma is considered a nervous system–based degenerative disease that is only partially influenced by ocular factors . Moreover, neuronal degeneration involving all parts of the central visual pathways was documented at autopsy in a patient who had advanced open-angle glaucoma and severe visual field losses in both eyes .
Central neuronal degeneration can be assessed noninvasively using diffusion tensor imaging (DTI) with calculation of fractional anisotropy (FA), which measures the orientation coherence of diffusion and provides information about axonal integrity .
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Materials and methods
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Results
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Table 1
FA Values in Different ROIs of Patients with Glaucoma and Controls
Localization FA Patients with Glaucoma Controls ROI 1 0.36 ± 0.11 0.42 ± 0.13 ROI 2 0.48 ± 0.15 ∗ 0.66 ± 0.12 ROI 3 0.32 ± 0.16 0.35 ± 0.17 ROI 4 0.21 ± 0.09 0.24 ± 0.07 ROI 5 0.40 ± 0.16 ∗ 0.57 ± 0.13 ROI 6 0.48 ± 0.17 ∗ 0.64 ± 0.11 ROI 7 0.44 ± 0.22 ∗ 0.53 ± 0.20
FA, fractional anisotropy; ROI, region of interest.
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Discussion
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Conclusions
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