title: DTI parameters of axonal integrity and demyelination of the optic radiation correlate with glaucoma indices.
abstract: BACKGROUND
  In glaucoma, damage of retinal ganglion cells may continue to the linked optic radiations. This study investigates the correlation of glaucoma severity indicators with parameters of axonal and myelin integrity of the optic radiations.
  
  
  METHODS
  In this observational case-control study, 13 patients with normal-tension glaucoma, 13 patients with primary open-angle glaucoma, and seven control subjects (mean age, 57.6 ± 12.5 years) were randomly selected for diffusion tensor imaging (DTI) of the optic radiations. The results of the frequency doubling test (FDT) and the HRT-based linear discriminant functions of Burk (BLDF) and Mikelberg (MLDF) were correlated with the mean of the fractional anisotropy (FA), apparent diffusion coefficient (ADC), and radial diffusivity (RD) of the optic radiations. Multiple correlation analysis, corrected for age, stage of cerebral microangiopathy, diagnosis group, and gender was conducted at increasing thresholds of linear anisotropy (C(L)) to reduce mismeasurements because of complex fiber situations.
  
  
  RESULTS
  The best correlations were found for BLDF with FA at C(L) threshold 0.3 (0.594, p = 0.001), with ADC at C(L) 0.4 (-0.511, p = 0.005), and with RD at C(L) 0.4 (-0.585, p = 0.001). MLDF correlated with FA at C(L) 0.4 (0.393, p = 0.035). The FDT score correlated with FA at C(L) 0 (-0.491, p = 0.007) and with RD at C(L) 0 (-0.375, p = 0.045).
  
  
  CONCLUSIONS
  In glaucoma, DTI-derived parameters of the axonal integrity (FA, ADC) and demyelination (RD) of the optic radiation are linked to HRT-based indices of glaucoma severity and to impairment of the spatial-temporal contrast sensitivity.
authors.affiliation: Department of Ophthalmology, University Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen, Germany. georg.michelson@uk-erlangen.de
authors.forename: Georg
authors.initials: G
authors.lastname: Michelson
authors.forename: Tobias
authors.initials: T
authors.lastname: Engelhorn
authors.forename: Simone
authors.initials: S
authors.lastname: Wärntges
authors.forename: Ahmed
authors.initials: A
authors.lastname: El Rafei
authors.forename: Joachim
authors.initials: J
authors.lastname: Hornegger
authors.forename: Arnd
authors.initials: A
authors.lastname: Doerfler
mesh_terms: D016880:Anisotropy; D001369:Axons / Q000473:pathology*; D016022:Case-Control Studies; D059345:Cerebral Small Vessel Diseases; D003711:Demyelinating Diseases / Q000175:diagnosis*; D056324:Diffusion Tensor Imaging; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D057066:Low Tension Glaucoma / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D012165:Retinal Ganglion Cells / Q000473:pathology; D055351:Retinal Neurons / Q000473:pathology*; D011795:Surveys and Questionnaires; D058609:Visual Field Tests; D014794:Visual Fields