Modelling floppy iris syndrome and the impact of pupil size
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The aim of this paper was to further develop a previously described finite element model that equates clinical iris billowing movements with mechanical buckling behavior, simulating floppy iris syndrome. Researchers wished to evaluate the impact of pupil dilation and mechanical devices on the normal iris and floppy iris models.

Theoretical mathematical modeling and computer simulations were used to assess billowing/buckling patterns of the iris under loading pressures for the undilated and dilated normal iris, the undilated and dilated floppy iris, and additionally with a mechanical ring device.

For the normal iris, billowing/buckling occurred at a critical pressure of 19.92?mmHg for 5?mm pupil size, which increased to 28.00?mmHg (40.56%) with a 7?mm pupil. The Malyugin ring device significantly increased critical initiating buckling pressures in the normal iris scenario, to 34.58?mmHg (73.59%) for 7?mm ring with boundary conditions I (BC I) and 34.51?mmHg (73.24%) with BC II. For the most floppy iris modeling (40% degradation), the initiating buckling value was 18.04?mmHg (-9.44%), which increased to 28.39?mmHg (42.52%) with the 7?mm ring. These results were much greater than for normal undilated iris without restrictive mechanical expansion (19.92?mmHg).

This simulation demonstrates that pupil expansion devices inhibit iris billowing even in the setting of floppy iris syndrome. This study also provides a model to further investigate the impact of pupil size or pharmacological interventions on anterior segment conditions affected by the iris position.