title: Torsion of the optic nerve head is a prominent feature of normal-tension glaucoma.
abstract: OBJECTIVE
  To compare optic nerve head (ONH) morphology between eyes with normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG).
  
  
  METHODS
  Seventy-eight NTG patients and 78 POAG patients matched according to age and axial length were analyzed. Optic nerve head tilt and torsion were identified from cross-sectional images of optical coherence tomography. The degree of horizontal, vertical, and maximum ONH tilt and torsion was compared between NTG and POAG eyes, and additional comparisons were based on the presence of myopia and the location of the visual field defect. Logistic regression analysis was used to determine the factors related to the degree of ONH torsion.
  
  
  RESULTS
  Vertical (P = 0.610) and horizontal tilt degree (P = 0.746) did not differ between NTG and POAG eyes. However, torsion degree (P = 0.022) differed significantly between NTG and POAG eyes. Direction of vertical tilt (P = 0.040) and torsion (P < 0.001) showed more prevalent superior tilt and torsion in NTG eyes (21.8% and 33.3%, respectively) compared to POAG eyes (10.3% and 10.3%, respectively). Myopic NTG eyes showed greater torsion degree (P = 0.014) than nonmyopic NTG eyes, which was not observed in the comparison between myopic and nonmyopic POAG eyes. Only NTG eyes showed a significant difference in the degree of maximum tilt (P < 0.001) and torsion (P < 0.001) and the direction of vertical tilt (P < 0.001) and torsion (P = 0.010) by the location of visual field defect. Longer axial length, maximum tilt degree, and diagnosis of NTG were the factors related to the degree of ONH torsion.
  
  
  CONCLUSIONS
  Normal-tension glaucoma eyes had a greater ONH torsion compared to POAG eyes with matched axial length. The direction of the ONH tilt and torsion was related to the location of the visual field defect only in NTG eyes.
authors.affiliation: Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, South Korea Seoul St. Mary's Hospital, Seoul, South Korea.
authors.forename: Hae-Young L
authors.initials: HY
authors.lastname: Park
authors.affiliation: Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, South Korea Seoul St. Mary's Hospital, Seoul, South Korea.
authors.forename: Kee-Il
authors.initials: KI
authors.lastname: Lee
authors.affiliation: Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, South Korea Seoul St. Mary's Hospital, Seoul, South Korea.
authors.forename: Kook
authors.initials: K
authors.lastname: Lee
authors.affiliation: Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, South Korea Uijungbu St. Mary's Hospital, Uijungbu, South Korea.
authors.forename: Hye Young
authors.initials: HY
authors.lastname: Shin
authors.affiliation: Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, South Korea Seoul St. Mary's Hospital, Seoul, South Korea.
authors.forename: Chan Kee
authors.initials: CK
authors.lastname: Park
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D057066:Low Tension Glaucoma / Q000150:complications / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000209:etiology / Q000473:pathology*; D012165:Retinal Ganglion Cells / Q000473:pathology; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods; D014102:Torsion Abnormality / Q000209:etiology / Q000473:pathology*; D014794:Visual Fields
keywords: myopia; normal tension glaucoma; optic disc torsion