Purpose:
In glaucoma damage of retinal ganglion cells may continue to the linked optic radiations (OR). Thus, correlation of examination results of the two visual pathway neurons may be meaningful. This study investigated the correlation of ophthalmologic examinations, which indicates glaucoma severity, with parameters, which represent the axonal integrity of OR as measured by diffusion tensor imaging (DTI), i.e. the fractional anisotropy (FA) and the apparent diffusion coefficient (ADC).
Methods:
Thirteen patients each with normal tension glaucoma or primary open angle glaucoma, and 9 control subjects with eye diagnosis, which do not affect the visual pathway (mean age, 57.7±12.4 years) underwent the frequency doubling test (FDT), Heidelberg retina tomography (HRT), and DTI. Magnetic resonance images did not show cerebral space occupying lesions along the visual pathway. The ORs in the DTI were outlined semi-automatically (see figure). The mean values of FA and ADC of the two ORs were measured. The mean FDT duration and mean FDT score of the two eyes were calculated. The HRT provided the Mikelberg discriminant function (MDF) and the Burk linear discriminant function (BLDF) related to glaucoma severity. Their means of the two eyes were calculated. Partial correlation analysis was performed corrected for age, stage of cerebral microangiopathy, glaucoma presence, and gender.
Results:
The fractional anisotropy in OR correlated with FDT duration (-0.418, p=0.019), FDT score (-0.457, p=0.010), Mikelberg discriminant function (0.376, p=0.037), and Burk linear discriminant function (0.586, p=0.001). Additionally, the apparent diffusion coefficient correlated with the Burk linear discriminant function (-0.369, p=0.041).
Conclusions:
DTI-derived parameters of the optic radiation axonal integrity are linked to HRT-based indices of glaucoma severity and to impairment of the spatial-temporal contrast sensitivity.
Keywords: imaging/image analysis: clinical • neuro-ophthalmology: diagnosis • visual impairment: neuro-ophthalmological disease