title: Correlation between biomechanical responses of posterior sclera and IOP elevations during micro intraocular volume change.
abstract: OBJECTIVE
  This study tested the hypothesis that intraocular pressure (IOP) elevations, induced by controlled increase of intraocular volume, are correlated with the biomechanical responses of the posterior sclera.
  
  
  METHODS
  Porcine globes were tested within 48 hours postmortem. The first group of globes (n = 11) was infused with 15 μL of phosphate-buffered saline at three different rates to investigate rate-dependent IOP elevations. The second group (n = 16) was first infused at the fast rate and then underwent inflation tests to investigate the relationship between IOP elevations (ΔIOP) and scleral strains. The strains in the superotemporal region of the posterior sclera were measured by ultrasound speckle tracking. Linear regression was used to examine the association between ΔIOP due to micro-volumetric infusion and the scleral strains at a specific inflation pressure.
  
  
  RESULTS
  The average ΔIOP was 14.9 ± 4.3 mm Hg for the infusion of 15 μL in 1 second. The ΔIOP was greater for the faster infusion rates but highly correlated across different rates (P < 0.001). A significant negative association was found between the ΔIOP and the tangential strains in both the circumferential (R(2) = 0.54, P = 0.003) and meridian (R(2) = 0.53, P = 0.002) directions in the posterior sclera.
  
  
  CONCLUSIONS
  This study showed a substantial increase in IOP, with a large intersubject variance during micro-volumetric change. A stiffer response of the sclera was associated with larger IOP spikes, providing experimental evidence linking corneoscleral biomechanics to IOP fluctuation. In vivo measurement of corneoscleral biomechanics may help better predict the dynamic profile of IOP.
authors.affiliation: Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio.
authors.forename: Hugh J
authors.initials: HJ
authors.lastname: Morris
authors.forename: Junhua
authors.initials: J
authors.lastname: Tang
authors.forename: Benjamin
authors.initials: B
authors.lastname: Cruz Perez
authors.forename: Xueliang
authors.initials: X
authors.lastname: Pan
authors.forename: Richard T
authors.initials: RT
authors.lastname: Hart
authors.forename: Paul A
authors.initials: PA
authors.lastname: Weber
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D007429:Intraocular Pressure / Q000502:physiology*; D009798:Ocular Hypertension / Q000503:physiopathology; D012044:Regression Analysis; D012590:Sclera / Q000000981:diagnostic imaging / Q000502:physiology*; D013314:Stress, Mechanical; D013552:Swine; D014463:Ultrasonography
keywords: IOP fluctuation; glaucoma posterior segment; scleral biomechanics