May 2007
Volume 48, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2007
Model of Pulsatile-Flow of Aqueous Humor Through the Iris-Lens Canal for the Prediction of Clinical Conditions Predisposing to Pupillary Block
Author Affiliations & Notes
  • M. Abdulrazik
    EJEIC, East-Jerusalem Eye Institute and Clinics, East-Jerusalem, Israel
  • Footnotes
    Commercial Relationships M. Abdulrazik, None.
  • Footnotes
    Support None.
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 1280. doi:https://doi.org/
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      M. Abdulrazik; Model of Pulsatile-Flow of Aqueous Humor Through the Iris-Lens Canal for the Prediction of Clinical Conditions Predisposing to Pupillary Block. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1280. doi: https://doi.org/.

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Abstract
 
Purpose:
 

To present a model of pulsatile-flow of aqueous humor from the posterior- (PC) to the anterior-chamber (AC), and to analyze the ability of this model to predict high risk clinical conditions predisposing to pupillary block.

 
Methods:
 

The model assumes non-continuous flow of aqueous humor through the iris-lens canal. Aqueous that fills the canal will be ejected toward the AC-side of the canal at certain time intervals, and between two events of aqueous ejection there is no actual flow through this canal. The PC-AC pressure gradient indicator of the present model is the pupillary pumping rate (PPR). PPR was calculated from the aqueous flow rate and the calculated volume of iris-lens canal ([PPR] = [aqueous flow rate] / [volume of iris-lens canal]).

 
Results:
 

PPR values were generated by incorporating pupillary diameter (PD, 1 to 8 mm), aqueous flow rate (AFR, 1 to 2.5 µl/min) and iris-lens canal width (w, 0.5 to 2 mm) and height (h, 3 to 9 µm) in numerical experimentation with the present model algorithm ([PPR] = [AFR] / [Pi . h . w . (w+PD)]). PPR showed inverse dependence on iris-lens canal height and pupillary diameter and was directly proportional to aqueous flow rate, in agreement with the steady-flow model of Silver and Quigley (J Glaucoma. 2004;13(2):100-7). However, contrary to the steady-flow model, PPR showed inverse dependence on iris-lens canal width and predicted the anticipated PC-AC pressure gradient changes in eyes of patients with clinically narrow angles and ultrasound biomicroscopy (UBM) evidenced pupillary block when their UBM measurements of the iris-lens contact width (w) were used (Figure 1).

 
Conclusions:
 

Upon the incorporation of clinical UBM measurements of the iris-lens contact width in numerical experimentations with both models, the present pulsatile-flow model, contrary to the steady-flow model, showed good predictability of PC-AC pressure gradient changes in a typical condition predisposing to pupillary block.  

 
Keywords: aqueous • pupil • pump/barrier function 
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