title: Effect of acute intraocular pressure elevation on blood flow velocity and resistance in the rabbit ophthalmic artery.
abstract: OBJECTIVE
  To determine the effect of intraocular pressure (IOP) on blood flow velocity and resistance in the rabbit ophthalmic artery.
  
  
  METHODS
  Ten adult New Zealand White rabbits were used.
  
  
  METHODS
  Right eyes were cannulated and the IOP was raised in a stepwise manner from 20 to 70 mmHg. Peak systolic velocity (PSV), end diastolic velocity (EDV) and resistive index (RI) in the ophthalmic artery were measured by color Doppler imaging. Values of PSV, EDV and RI were compared at various IOPs via the analysis of variance (anova) of a randomized block design with post hoc Bonferroni test.
  
  
  RESULTS
  Significant differences of PSV, EDV and RI at different IOP points (all P < 0.001) were observed. Over the entire IOP range, linear regression showed a negative correlation between IOP and both PSV and EDV (β = -0.07434, P = 0.0020 and β = -0.07829, P < 0.001, respectively), as well as a positive correlation between the RI and IOP (β = 0.00221, P < 0.001). Moreover, line plots identified a point with IOP = 40 mmHg, splitting the IOP range with different regression slopes. Piecewise linear regression indicated no correlation between PSV, EDV, RI and IOP when the IOP was elevated from 20 to 40 mmHg (P = 0.1832, P = 0.5932 and P = 0.5819, respectively). However, piecewise linear regression detected a stronger negative correlation between PSV, EDV and IOP (β = -0.15760, P = 0.0011 and β = -0.11872, P = 0.001, respectively) and a stronger positive correlation between RI and IOP (β = 0.00273, P = 0.0015) during the stage from 40 to 70 mmHg.
  
  
  CONCLUSIONS
  The ophthalmic artery in the rabbits was capable of maintaining normal blood velocity and resistance when IOP was below 40 mmHg. However, the autoregulatory capacity was greatly limited when IOP was over 40 mmHg.
authors: Department of ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, China.
authors: Qiang
authors: Q
authors: Yang
authors: Jiying
authors: J
authors: Shen
authors: Wenyi
authors: W
authors: Guo
authors: Jiexian
authors: J
authors: Wen
authors: Zhongfeng
authors: Z
authors: Wang
authors: Daoyi
authors: D
authors: Yu
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D005260:Female; D005901:Glaucoma / Q000503:physiopathology / Q000662:veterinary; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D009880:Ophthalmic Artery / Q000000981:diagnostic imaging / Q000502:physiology* / Q000503:physiopathology; D011817:Rabbits; D018615:Ultrasonography, Doppler, Color / Q000662:veterinary; D014655:Vascular Resistance / Q000502:physiology