Fig 1.
A. Anatomy of the iris tissue. The iris consists of the anterior boundary layer (ABL), the stroma, the sphincter and dilator muscles, and the posterior pigmented epithelium (PE). B. Geometry of the FE model used for simulations. The stroma and the ABL were combined into a single part, and the sphincter and dilator muscles were combined with the PE.
Fig 2.
Anatomical orientation convention adopted in this study.
The orientation adopted is in Cartesian coordinates in the x, y and z directions. The iris of a left eye is shown in this figure. The direction conventions of the arrows are perpendicular to their respective planes.
Fig 3.
The FE models and summary of the simulation parameters used in the analyses for A. The iris hooks, B. The APX dilator, C. The Malyugin ring, and for D. Uniform circular expansion. All irides had an initial pupil diameter of 3 mm (initial shape). Following FE analysis, the deformed expanded pupil shapes had diameters of 6 mm (maximum observable diameter, expanded shape).
Table 1.
Results of FE stroma and muscle stress values, and reaction forces experienced by the iris with the various pupil expanders.
Fig 4.
A. Initial iris shape with a pupil diameter of 3 mm before pupil expansion. Stress distribution of the iris tissue with the use of B. APX dilator, C. Iris hooks, D. Malyugin ring and E. Uniform circular expansion. The FE models were all deformed to a 6 mm pupil and stress magnitudes adjusted to the same scale. F. Graph of stromal stress along the radial direction starting at the point of greatest stress concentration (marked using solid black lines in B-E) and along the radial direction where a corner is present (marked using dotted black lines in B-E). Note that the starting point of each curve is determined by the size of the pupil and the ends at the iris limbus.
Table 2.
Comparison of all results with uniform circular expansion as the baseline.
The sign (+) refers to “greater than” and the sign (-) refers to “smaller than”.