Mathematical and computer simulation modelling of intracameral forces causing pupil block due to air bubble use in Descemet's Stripping Endothelial Keratoplasty: the mechanics of iris buckling

Abstract

This model shows how iris buckling could occur with an intracameral air bubble leading to posterior iris displacement and mechanical pupil block. It also shows that abnormal iris behaviour in IFIS is consistent with the expected predicted buckling of an elastic disc.

Corneal Transplantation and Glaucoma

“…Mathematical models of floppy iris syndrome, which exhibits a reduced modulus of elasticity of the iris, suggest that these eyes may be more vulnerable to problems with air bubble placement. 171 Pupillary block and aqueous misdirection have also been reported. 172 Nieuwendaal reports 8% of patients on post-operative day 1 requiring intervention for OHTN likely secondary to the air bubble.…”

Can we trust intraocular pressure measurements in eyes with intracameral air?

“…However, a significant IOP spike directly after a DSEK/DMEK surgery is a known complication [5], and a correct estimation of the IOP is essential for postoperative care. A rise in IOP post-operatively may be due to secondary angle closure due to air moving behind the pupil and consequently causing a pupillary block [3][4][5]. However, pupillary block is not the only cause of acute IOP rise after DSEK/DMEK.…”

“…In order to keep the transplant in place, air is injected into the anterior chamber at the end of surgery. This can cause acute increases in intraocular pressure (IOP) [3][4][5][6], necessitating various interventions such as tapping air from the anterior chamber or administering IOP-lowering medications. In order to handle the situation correctly, accurate IOP measurement is crucial.…”

Optimum size of iridotomy in uveitis

“…There are other factors in (Fig. 2a): (a) the iris modelled as a deformable elasticated disc with a central circular aperture, 10 the cornea and the lens are assumed to be rigid and impermeable. (b) Computations of the iris shape as a function of trans-iris pressure difference were conducted in the Finite Element software ABAQUS 6.13 (SIMULIA, Providence, RI), assuming the iris to be of uniform initial thickness h with elastic moduli listed in Table 1.…”

“…[7][8][9][10] Parameters such as the aqueous viscosity and the iris stiffness and thickness will be dependent on the pathology of the disease and these values can only be estimated.…”