Active iris mechanics and pupillary block: Steady-state analysis and comparison with anatomical risk factors

Eric C. Huang, Victor H. Barocas

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


Primary angle-closure glaucoma arises when the iris physically obstructs outflow of aqueous humor, increasing the intraocular pressure and damaging the optic nerve. Pupillary block, the predominant mechanism for angle closure, is believed to be driven by mechanical interaction between the aqueous humor and the iris. We performed steady-state simulations of this coupled fluid-solid system, including an active sphincter to control pupil constriction. Model results compared favorably against Map-stone's pupil-blocking force analysis. We also evaluated anatomical risk factors and quantified their contributions to pupillary block and angle closure. The results showed that greater lens curvature and shorter iris-zonule distance contribute significantly to pupillary block and the associated narrowing of the angle. Surprisingly, the model predicted that maximum pupillary block and angle closure occur at the minimum pupil dilation, contradicting the clinical observation that angle closure is most severe in dark conditions. This discrepancy suggests the involvement of one or more phenomena not captured by our current model.

Original languageEnglish (US)
Pages (from-to)1276-1285
Number of pages10
JournalAnnals of Biomedical Engineering
Issue number9
StatePublished - Sep 2004

Bibliographical note

Funding Information:
We thank Jeffrey J. Heys for providing advice during simulation development. This work was supported by a Biomedical Engineering Research Grant from the Whitaker Foundation and by the University of Minnesota Biomedical Engineering Institute. Computer simulations were made possible by a Supercomputing Resource Grant from the University of Minnesota Supercomputing Institute for Digital Simulation and Advanced Computation.

Copyright 2013 Elsevier B.V., All rights reserved.


  • Angle closure
  • Anterior chamber diameter
  • Aqueous humor
  • Eye
  • Fluid-structure interaction
  • Glaucoma
  • Pupil-blocking force
  • Pupillary block


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