Little is known about the Darcy permeability of the choroidal tissue,
\(k_{\mathcal {C}}\), except that it is larger than that of the sclera,
96 and little is known about the resistance to flow of the tissue of the iris root and ciliary muscle,
Ricm. In addition, little is known about the SCS thickness
\(h_{\mathcal {P}0}\); for example, in their experiments on rabbits, Chiang et al.
97 assumed that the physiological SCS thickness was less than 25 µm, which is not specific enough for our model. To set these three unknown model parameters for the reference physiological case, we (1) make the model match the IF pressures at the inlet and the pole to the values measured by Emi et al., which (for physiological values of the IOP) are 0.8 ± 0.2 mm Hg and 3.7 ± 0.5 mm Hg lower than the IOP at the anterior and posterior of the SCS, respectively,
58 and (2) set the proportions of the unconventional flow that pass through the choroidal tissue and the SCS at the inlet. This means that, if we change this proportion, we also need to adjust the parameters
\(k_\mathcal {C}\) and
Ricm to reproduce the pressures at the inlet and the pole. In
Figure A1A, we show how changing this proportion (and correspondingly changing
\(k_\mathcal {C}\) and
Ricm) affects the unconventional flow. Even over the range 5% to 100%, the unconventional flow only changes by appropriately 10%, suggesting that the model is not very sensitive to the chosen value of this proportion. In summary, we choose
kC,
Ricm and
hP0 so that the IF pressures at the inlet and posterior are 14.2 and 11.3 mm Hg, respectively, and the proportion of the unconventional flow that passes through the choroidal tissue is 50% at the inlet.