Trabecular bypass: effect of schlemm canal and collector channel dilation

To theorize the effect of Schlemm canal (SC) and/or collector channel (CC) dilation combined with a trabecular bypass on intraocular pressure (IOP) in eyes with primary open angle glaucoma.

The elliptic shaped SC is dilated in conjunction with a trabecular bypass and its expanded height is largest at the bypass and linearly deceases to the nondilated height over the dilated circumferential length. The CC dilation is modeled with a reduced outflow resistance of second order polynomial over the same dilated length. Equations governing the pressure and circumferential flow in SC are solved numerically for both the unidirectional and bidirectional bypasses. The reduced IOP is deduced from the solution.

IOP is reduced substantially with moderate SC dilation from the normal height of 20 microm to 40 to 50 microm at the bypass; additional IOP reduction diminishes with further dilation. SC dilation is more effective for eyes with smaller SC. CC dilation also lower IOP significantly. With the trabecular bypass alone, the elevated IOP in primary open angle glaucoma is expected to drop to the mid-to-high teens. IOP can be further reduced by another 3 to 6 mm Hg with moderate SC and CC dilation. The circumferential length of dilated SC affects the efficacy of IOP reduction. In theory, the dilation of SC with a trabecular bypass is analogous to a partial trabeculotomy in terms of IOP reduction.

In theory, a moderate dilation of SC and CC in conjunction with a trabecular bypass reduces the IOP to the low-to-mid teens.