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G. Michelson, S. Waerntges, T. Engelhorn, A. Doerfler; Reduction of the Optic Radiation Volume Measured by DTI Is Correlated With Cerebral Microangiopathy in Normal Tension Glaucoma. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5865.
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The causation of primary open angle glaucoma (POAG) and particularly, its subgroup normal tension glaucoma (NTG) is not yet completely understood. These types of glaucoma may be regarded as systemic vessel diseases associated with ischemia-induced neuronal degeneration - as well as cerebral microangiopathy. As indication is provided that the optic radiation (OR) of the visual pathway may be damaged in glaucoma and/ or cerebral microangiopathy, we examined if degeneration of the optic radiation is associated with cerebral microangiopathy in POAG patients.
In this prospective observational study 17 patients with POAG without suspicion for NTG and 11 patients diagnosed with NTG (age 57±12 years and 61±12 years, respectively, p=0.38) were randomly selected and examined by T2-weighted magnetic resonance imaging (MRI) for cerebral microangiopathy and by diffusion tensor imaging (DTI) for a rarefied optic radiation. No stroke or cerebral tumour was diagnosed in the MRI. The optic radiation in the DTI was manually outlined, the volume was calculated, and compared to age-adjusted controls.
In POAG patients without NTG the lower microangiopathy stages dominated (76 % stage 0 and 1 versus 24 % stage 2 and 3). In NTG patients predominantly higher microangiopathy stages were found (45 % stage 0 and 1 versus 55 % stage 2 and 3). In 24% of POAG and in 36% of NTG patients microangiopathy was found directly in the optic radiation (p = not significant). In NTG patients the right and left optic radiation volume, respectively, correlated negatively with the stage of microangiopathy. Non-parametric Kendall-tau-b for ordinal subordinated variables was -0.38, p<0.01 (right OR) and -0.57, p<0.05 (left OR). In POAG patients without suspicion for NTG this correlation was absent.
The pathophysiological difference between POAG patients and their NTG subgroup may consist in the influence of the more advanced generalized cerebral microangiopathy on the damage of the optic radiation in NTG patients.
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