Abstract

P 126

Relation between homonymous visual field defects and optic radiation volumetry in glaucoma patients

Simone Wärntges1, Arnd Dörfler2, Tobias Engelhorn2, Georg Michelson1
1Universitäts-Augenklinik Erlangen, 2Neuroradiologie, Klinik für Radiologie, Universitätsklinikum Erlangen, Erlangen

Background and goal
In glaucoma damage of retinal ganglion cells continues to the linked optic radiation (OR) by transneuronal degeneration. Additionally, local ischemia of the visual pathway may contribute to an impaired visual field. This study compared the homonymous visual fields of patients with normal tension glaucoma (NTG) with other primary open angle glaucoma (POAG) unsuspicious for NTG in relation to the volumetric measured optic radiation.
Methods
Eleven patients with POAG suspicious for NTG (age, 61±12 years) and 17 patients with POAG unsuspicious for NTG (age, 57±12 years, p = not significant) were randomly selected and examined by diffusion tensor imaging (DTI) for a rarefied optic radiation. Magnetic resonance images did not show strokes or cerebral tumours. The optic radiation in the DTI was manually outlined, the volume was calculated, and the percentage difference to age-adjusted controls was evaluated. Age was not different between groups with normal or reduced OR within the NTG and POAG group, respectively. The homonymous visual field defects were calculated.
Results
In NTG patients with reduced optic radiation volume the homonymous mean defect (corresponding to the right optic radiation, 10.3±5.1 dB, and the left OR, 10.0±4.5 dB) was significantly larger compared to NTG patients with normal optic radiation volume (3.4±5.6 dB, right OR, and 3.4±4.6 dB, left OR; p=0.045 and p=0.028; power 57% and 67%, resp.). In NTG the percentage volume of OR correlated negatively with the grade of the calculated homonymous visual field defects (Kendall-tau-b -0.56, p=0.002 for the right OR and -0.58, p=0.005 for the left OR). In POAG without suspicion for NTG such differences and correlations were not found.
Conclusion
In NTG patients the visual field defect might be related also to a damage of the optic radiation.

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