May 2005
Volume 46, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2005
Ocular Blood Flow in the Rat During Acute Elevation of Intraocular Pressure
Author Affiliations & Notes
  • L. Wang
    Dicoveries in Sight, Devers Eye Institute, Portland, OR
  • B. Fortune
    Dicoveries in Sight, Devers Eye Institute, Portland, OR
  • G. Cull
    Dicoveries in Sight, Devers Eye Institute, Portland, OR
  • B. Bui
    Dicoveries in Sight, Devers Eye Institute, Portland, OR
  • G.A. Cioffi
    Dicoveries in Sight, Devers Eye Institute, Portland, OR
  • Footnotes
    Commercial Relationships  L. Wang, None; B. Fortune, None; G. Cull, None; B. Bui, None; G.A. Cioffi, None.
  • Footnotes
    Support  Legacy RAC, NIH EY05231
Investigative Ophthalmology & Visual Science May 2005, Vol.46, 1331. doi:
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      L. Wang, B. Fortune, G. Cull, B. Bui, G.A. Cioffi; Ocular Blood Flow in the Rat During Acute Elevation of Intraocular Pressure . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1331.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract 
 
Abstract:
 

 

Elevation of intraocular pressure (IOP) results in ocular structural damage and functional loss. In models of glaucoma, these changes appear to be proportional to the degree of IOP elevation and altered ocular blood flow (BF) is likely to have a causative role at some level of IOP. The purpose of this study was to determine the effects of acute IOP elevation on retinal and choroidal blood flow in the rat.

 

 

BF was determined using the microspheres (MS) method. Under isoflurane anesthesia, the anterior chamber of one eye of each rat was cannulated. IOP was controlled manometrically, while the fellow eye served as control. The femoral arteries were cannulated for direct measurement of mean arterial pressure (MAP) and reference blood sampling. A femoral vein was cannulated for intravenous admininstration of indomethacin (5 mg/kg) and heparin (200 USP units). Fluorescent MS (107 in 0.6 ml BSS, 4.5–6.0 µm diameter) were injected into the left ventricle over a 40–60 sec period without disturbing the MAP. The retina and choroid of each eye were flat mounted seperately. The total number of MS in each tissue sample was counted by a masked observer using an automated image analysis system. The number of MS was divided by the concentration of MS in the reference sample (#/µl/min) to determine tissue BF (µl/min).

 

 

In control animals (neither eye cannulated), mean BF (±SD) in the retina and choroid were 6.4 ± 1.2 and 21.8 ± 9.0 µl/min, respectively. Relative BF (experimental eye/control eye) was inversely related to perfusion pressure (MAP – IOP) in both retina (r2 = 0.76, P < 0.0001) and choroid (r2 = 0.72, P < 0.0001). Significant interocular BF differences were observed for both the retina and choroid in the groups that had IOP elevated to 40, 50, 70, and 100 mm Hg, but not in the control group (Table).

 

 

The differential effect of IOP on retinal versus choroidal BF is smaller in rats than previously reported in primates. Acute elevation of IOP to 40 mm Hg or above causes significant reduction of blood flow in both the retina and choroid of the rat eye and may partly explain previously observed changes in retinal structure and function in rodent models of glaucoma.

 

 

 
Keywords: intraocular pressure • blood supply 
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