May 2007
Volume 48, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2007
Dorzolamide and Brimonidine: Two Oppositional Mechanisms of Reducing Aqueous Humour Formation in Acute Rabbit Experiments
Author Affiliations & Notes
  • B. Bogner
    Ophthalmology/Optometry, Paracelsus University, Salzburg, Austria
  • B. Tockner
    Ophthalmology/Optometry, Paracelsus University, Salzburg, Austria
  • C. Runge
    Ophthalmology/Optometry, Paracelsus University, Salzburg, Austria
  • G. Grabner
    Ophthalmology/Optometry, Paracelsus University, Salzburg, Austria
  • J. W. Kiel
    Ophthalmology, University of Texas Health Science Center, San Antonio, Texas
  • H. A. Reitsamer
    Ophthalmology/Optometry, Paracelsus University, Salzburg, Austria
  • Footnotes
    Commercial Relationships B. Bogner, None; B. Tockner, None; C. Runge, None; G. Grabner, None; J.W. Kiel, None; H.A. Reitsamer, None.
  • Footnotes
    Support Fuchs-Stiftung, Adele Rabensteiner Stiftung, NIH EY09702, FWFJ1866-MED
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 3931. doi:https://doi.org/
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      B. Bogner, B. Tockner, C. Runge, G. Grabner, J. W. Kiel, H. A. Reitsamer; Dorzolamide and Brimonidine: Two Oppositional Mechanisms of Reducing Aqueous Humour Formation in Acute Rabbit Experiments. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3931. doi: https://doi.org/.

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Abstract
 
Purpose:
 

To investigate the effect of topical dorzolamide on ciliaryblood flow (CilBF) and aqueous flow (AqF) in relation to theeffect of brimonidine on the two variables.

 
Methods:
 

In anesthetized rabbits mean arterial pressure (MAP), intraocularpressure (IOP) and orbital venous pressure (OVP) were measuredby direct cannulation of the central ear artery, the vitreous,and the orbital venous sinus, respectively. Laser Doppler flowmetrywas used to record CilBF continuously. Aqueous flow (AqF) wasmeasured simultaneously by flourophotometry. After baselinemeasurements either dorzolamide or brimonidine was applied topically.

 
Results:
 

The effect of dorzolamideon CilBF is caused by a significant reduction of ciliary bodyvascular resistance (CilR) while the effect of brimonidine iscaused by a significant increase in CilR. Topical dorzolamidehad no significant effect on MAP and heart rate, brimonidinealso had no effect on MAP but decreased heart rate significantly 

 

 
Conclusions:
 

We conclude that dorzolamide increases CilBF by reducing vascularresistance, an effect that is independent of the decrease inIOP. The reduction in AqF is primarily caused by dorzolaminde’sdirect inhibition of aqueous secretion and is not due to ciliaryvasoconstriction. However, on the other hand, vasoconstrictionseems to be the predominant mechanism by which brimonidine lowersaqueous production in the acute anesthetized rabbit preparation(see figure).

 
Keywords: ciliary body • blood supply • aqueous 
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