Fig 1.
Aqueous humor artificial drainage pathway.
Schematic representation of the artificial drainage pathway of aqueous humor into the subconjunctival space, where a filtering bleb is formed, following glaucoma drainage device insertion.
Fig 2.
Schematics showing the PRESERFLO® Microshunt dimensions and placement in the eye [18].
Fig 3.
Two-dimensional geometry of the filtering bleb.
(A) Shape and dimensions of a healthy bleb and overlying conjunctival/Tenon’s tissue based on a cross-sectional Optical Coherence Tomography (OCT) image (patient with an IOP of 10 mmHg); these dimensions were used to simulate the normal (healthy/well-functioning bleb) and hypotony cases. (B) Shape and dimensions of the bleb, scar tissue layer, and subconjunctival tissue used to simulate the bleb scarring scenario.
Fig 4.
2D-axisymmetric computational domain of the subconjunctival drainage of aqueous humor through a hollow tube-like microshunt.
The bleb dimensions are as in Fig 3 and a scar tissue layer may be included as in Fig 3B. The applied boundary conditions are indicated in red.
Table 1.
Parameter values used in the simulations.
Table 2.
Boundary conditions used in the simulations for the shunt and bleb/scar layer/subconjunctival tissue domains.
Fig 5.
Design of the microfluidic devices.
Schematic illustration of the design of the microfluidic devices used for the model validation (right side). The bottom and top layers the microdevice is made of are shown on the left side.
Table 3.
Dimension of the channels of the microfluidic chips and corresponding tube diameters.
Fig 6.
Setup used for the microfluidic experiments.
Fig 7.
Interstitial pressure distribution in the subconjunctival space.
Model prediction of the interstitial pressure distribution in the subconjunctival space in the presence of hypotony, healthy/well-functioning bleb, and encapsulated bleb (scar layer with hydraulic conductivity of 2x10−13 m2 s−1 Pa−). In all cases, the PRESERFLO MicroShunt is used as the glaucoma drainage device. Color scale indicates interstitial fluid pressure in mmHg.
Fig 8.
Bleb pressure (pbleb) and IOP calculated for each of the case-scenarios studied: Hypotony, healthy bleb, and encapsulated bleb.
For the latter case, the hydraulic conductivity of the scar layer varies from 1 −3x10−13 m2 s−1 Pa−1. In all cases, the PRESERFLO MicroShunt is used as the glaucoma drainage device. The shaded green area represents an acceptable IOP range of 5–15 mmHg.
Fig 9.
Model prediction of the IOP with varying MicroShunt lumen diameters.
(A) and (B)–IOP variation with varying MicroShunt lumen diameter in case of hypotony and encapsulated bleb, respectively. (C) and (D)–Hydrodynamic resistance (r) of the different lumen-diameter MicroShunts and its impact on the final IOP. The shaded green area represents an acceptable IOP range of 5–15 mmHg.
Fig 10.
Fabricated microfluidic devices.
(A) FEMTOprint glass mold used for the fabrication of the bottom layers of the microfluidic chips (in this case, for the encapsulated model validation devices). (B) SIBS bottom layer of the encapsulated model validation device replicated from the mold. (C) Final microdevice used in the microfluidic experiments.
Fig 11.
Calculated IOP vs. experimental IOP.
Comparison between the IOPs calculated with the model and the IOPs measured in the microfluidic experiments in case of (A) hypotony and (B), (C) and (D) bleb encapsulation, and for different shunt lumen diameters/channel dimensions.