Purpose:
The impact of myelin along the third and fourth neuron of the visual pathway in glaucoma is not completely elucidated. The pattern of myelin basic protein and glial fibrillary acidic protein was found to be different in primary open angle glaucoma (POAG) and normal tension glaucoma (NTG) compared to controls. In mouse models the radial diffusivity (RD), suggested to represent demyelination or glia cell impairment, was shown to be specific for optic nerve injury. RD may be measured by diffusion tensor imaging (DTI). This study examined the correlation of a HRT-derived parameter of glaucoma stage, i.e. the Burk linear discriminant function (BLDF), with RD to discover a relation between glaucoma severity and damage of the covering material of the optic radiation axons.
Methods:
Thirteen NTG-patients, 13 POAG-patients and 9 control subjects with eye diagnosis, which do not affect the visual pathway (mean age, 57.7±12.4 years) underwent Heidelberg retina tomography (HRT) and DTI. Magnetic resonance images did not show cerebral space occupying lesions along the visual pathway. The optic radiation in the DTI was outlined semi-automatically (see figure) and the mean value of RD of the two ORs was measured. The values of BLDF related to glaucoma stage were derived from the HRT and the mean of both eyes was calculated.
Results:
If corrected for age, stage of cerebral microangiopathy, disease presence, and gender partial correlation analysis disclosed a correlation between RD and BLDF in the optic radiation (-0.478, p=0.006).
Conclusions:
In glaucoma demyelination or glia cell impairment as measured by the radial diffusivity in DT images of the optic radiation is suggested to increase with decreasing Burk linear discriminant function, i.e. with increasing glaucoma severity.
Keywords: imaging/image analysis: clinical • neuro-ophthalmology: diagnosis • visual impairment: neuro-ophthalmological disease