title: Parapapillary Gamma Zone and Axial Elongation-Associated Optic Disc Rotation: The Beijing Eye Study.
abstract: OBJECTIVE
  The parapapillary gamma zone has been defined as the parapapillary region without Bruch's membrane. We examined which morphologic parameters are associated with the presence and size of the parapapillary gamma zone.
  
  
  METHODS
  Using fundus photographs and spectral-domain optical coherence tomographic images of the optic nerve head in the population-based Beijing Eye Study, we determined parapapillary gamma zone width, macular Bruch's membrane length, optic disc-fovea distance, the angle of horizontal optic disc rotation, the angle of vertical optic disc rotation, and the ratio of the vertical-to-horizontal disc diameter.
  
  
  RESULTS
  The study included 2068 individuals with a mean age of 63.0 ± 9.0 years (range, 50-91 years), and mean axial length was 23.2 ± 1.0 mm (range, 18.96-28.87 mm). In multivariate analysis, larger width of parapapillary gamma zone was associated with more marked vertical optic disc rotation (P < 0.001; standardized correlation coefficient β, 0.15; nonstandardized correlation coefficient B, 0.02; 95% confidence interval [CI], 0.02, 0.03), more marked horizontal optic disc rotation (P = 0.02; β, 0.05; B, 0.01; 95% CI, 0.001, 0.01), longer axial length (P = 0.01; β, 0.07; B, 0.02; 95% CI, 0.01, 0.04), longer horizontal optic disc diameter (P = 0.02; β, 0.05; B, 0.06; 95% CI, 0.01, 0.12), longer disc-fovea distance (P < 0.001; β, 0.25; B, 0.22; 95% CI, 0.18, 0.27), higher degree of fundus tessellation (P = 0.03; β, 0.17; B, 0.04; 95% CI, 0.03, 0.0), and thinner subfoveal choroidal thickness (P < 0.001; β, -0.13; B, 0.000; 95% CI, -0.001, 0.000). Parapapillary gamma zone width was not significantly associated with macular Bruch's membrane length (P = 0.72), disc-fovea angle (P = 0.62), age (P = 0.62), or sex (P = 0.46).
  
  
  CONCLUSIONS
  The parapapillary gamma zone was associated with an axial elongation-induced rotation of the optic disc mainly around the vertical disc axis, leading to a stretching of the temporal peripapillary scleral flange. Because macular Bruch's membrane length was independent of axial elongation, it leaves the temporal parapapillary region with an uncovered Bruch's membrane (i.e., parapapillary gamma zone develops).
authors: Beijing Institute of Ophthalmology Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Lab, Beijing, China 2Department of Ophthalmology, Medical Faculty Mannheim of the Ruprecht-Ka.
authors: Jost B
authors: JB
authors: Jonas
authors: Beijing Institute of Ophthalmology Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Lab, Beijing, China.
authors: Ya Xing
authors: YX
authors: Wang
authors: Beijing Institute of Ophthalmology Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Lab, Beijing, China.
authors: Qi
authors: Q
authors: Zhang
authors: Beijing Tongren Eye Center, Beijing Key Laboratory of Intraocular Tumor Diagnosis and Treatment, Beijing Tongren Hospital, Capital Medical University, Beijing, China.
authors: Yuan Yuan
authors: YY
authors: Fan
authors: Beijing Institute of Ophthalmology Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Lab, Beijing, China.
authors: Liang
authors: L
authors: Xu
authors: Beijing Tongren Eye Center, Beijing Key Laboratory of Intraocular Tumor Diagnosis and Treatment, Beijing Tongren Hospital, Capital Medical University, Beijing, China.
authors: Wen Bin
authors: WB
authors: Wei
authors: Department of Ophthalmology, Medical Faculty Mannheim of the Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany.
authors: Rahul A
authors: RA
authors: Jonas
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D058452:Axial Length, Eye / Q000473:pathology*; D016570:Bruch Membrane / Q000473:pathology; D002681:China; D003430:Cross-Sectional Studies; D005260:Female; D005584:Fovea Centralis / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000473:pathology; D009896:Optic Atrophy / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D041623:Tomography, Optical Coherence