title: Laminar and prelaminar tissue displacement during intraocular pressure elevation in glaucoma patients and healthy controls.
abstract: OBJECTIVE
  To determine the response of the anterior lamina cribrosa and prelaminar tissue to acute elevation of intraocular pressure (IOP) in glaucoma patients and healthy subjects.
  
  
  METHODS
  Prospective case-control series.
  
  
  METHODS
  Patients with open-angle glaucoma (n = 12; mean age ± standard deviation [SD], 66.8 ± 6.0 years), age-matched healthy controls (n = 12; mean age ± SD, 67.1 ± 6.2 years), and young controls (n = 12; mean age ± SD, 36.1 ± 11.7 years).
  
  
  METHODS
  One eye was imaged with spectral-domain optical coherence tomography to obtain 12 high-resolution radial scans centered on the optic disc. Imaging was repeated at precisely the same locations with an ophthalmodynamometer held perpendicular to the globe via the inferior lid to raise the IOP. A line joining Bruch's membrane opening in 4 radial scans was used as reference in the baseline and elevated IOP images. The vertical distance from the reference line to the anterior prelaminar tissue surface and anterior laminar surface was measured at equidistant points along the reference line in the 2 sets of images. The difference between the 2 sets of corresponding measurements were used to determine laminar displacement (LD) and prelaminar tissue displacement (PTD).
  
  
  METHODS
  Laminar displacement and PTD.
  
  
  RESULTS
  Intraocular pressure elevation among patients, age-matched controls, and young controls was similar (mean ± SD, 12.4 ± 3.2 mmHg). The mean ± SD LD and PTD were 0.5 ± 3.3 μm and 15.7 ± 15.5 μm, respectively. The LD was not statistically different from 0 (P = 0.366), but PTD was (P < 0.001). The mean ± SD LD was similar among the groups (-0.5 ± 3.7 μm, 0.2 ± 2.0 μm, and 2.0 ± 3.6 μm, respectively; P = 0.366), whereas the mean ± SD PTD was different (6.8 ± 13.7 μm, 20.8 ± 17.5 μm, and 19.6 ± 11.8 μm, respectively; P = 0.045). In all subjects, the PTD was greater than LD. In multivariate regression analyses, LD was negatively associated with optic disc size (P = 0.007), whereas PTD was positively associated with the degree of IOP elevation (P = 0.013).
  
  
  CONCLUSIONS
  In glaucoma patients and controls, the anterior laminar surface is noncompliant to acute IOP elevation. Acute optic disc surface changes represent compression of prelaminar tissue and not laminar displacement.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Canada. bal@dal.ca
authors.forename: Younes
authors.initials: Y
authors.lastname: Agoumi
authors.forename: Glen P
authors.initials: GP
authors.lastname: Sharpe
authors.forename: Donna M
authors.initials: DM
authors.lastname: Hutchison
authors.forename: Marcelo T
authors.initials: MT
authors.lastname: Nicolela
authors.forename: Paul H
authors.initials: PH
authors.lastname: Artes
authors.forename: Balwantray C
authors.initials: BC
authors.lastname: Chauhan
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D009798:Ocular Hypertension / Q000503:physiopathology; D009884:Ophthalmodynamometry; D009898:Optic Disk / Q000503:physiopathology*; D011446:Prospective Studies; D041623:Tomography, Optical Coherence; D014065:Tonometry, Ocular