Biomedical subjects

Jianbo Zhou

Publications and source records attributed to Jianbo Zhou.

3 recordsLinked to original sources

PubMed2006

Trabecular bypass: effect of schlemm canal and collector channel dilation.

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

Aqueous Humor↗

PubMed2005

A trabecular bypass flow hypothesis.

PURPOSE: To introduce a hypothesis that theorizes the effect of a trabecular bypass, a channel created through the trabecular meshwork, on the facility of outflow and the intraocular pressure (IOP). METHODS: Equations that govern the pressure and circumferential flow in Schlemm's canal are established, based on the linear relationships between pressure drop and flow, the balance of flows in the canal, and a uniform leaking structure of collector channels. Two types of bypasses permitting either unidirectional or bidirectional flow are incorporated through boundary conditions to solve the equations and to derive the facility of outflow and the reduced IOP. RESULTS: In normal healthy eyes, the facility of outflow increases by 13% and 26% in the presence of a unidirectional and bidirectional bypass, respectively. The circumferential flow is significant only in the immediate quadrant to the bypass. The elevated IOP due to the abnormally high resistance in trabecular meshwork in open angle glaucoma is substantially reduced with a single bypass. Mean physiological level of IOP is attained if the bidirectional bypass is placed; slightly higher IOP is attained if a unidirectional bypass is placed. In either case, the higher the baseline IOP, the greater the reduction. The effectiveness of the bypass on IOP reduction is related to the resistances in the canal and the collector channels. Multiple bypasses can be used to further reduce the IOP. CONCLUSION: It is theoretically demonstrated that a single patent trabecular bypass can enhance the facility of outflow and reduce the IOP to physiological levels.

Aqueous Humor↗

PubMed2004

Trabecular bypass stents decrease intraocular pressure in cultured human anterior segments.

PURPOSE: To determine the effect on intraocular pressure (IOP) of bypassing the trabecular meshwork in cultured human anterior segments. DESIGN: Prospective laboratory investigation using normal human eyes obtained at autopsy. METHODS: Anterior segments from 21 eyes were placed in perfusion culture, and trabecular bypass stents were inserted through the trabecular meshwork, with the lumen of the tube opening into Schlemm's canal. Eyes received from one to four stents, placed equidistant apart. In eyes receiving one or two stents, additional stents were later added to a maximum of four per eye. RESULTS: Intraocular pressure was lowered after placement of a single stent, from 21.4 +/- 3.8 mm Hg to 12.4 +/- 4.2 (P < .001). This corresponded to an 84% increase in facility of outflow. Eyes receiving more than one stent had final IOP of 11.9 +/- 3.7 mm Hg. Nine eyes had sequential addition of stents, and seven of these had a further decrease of IOP (13.6 +/- 4.1 to 10.0 +/- 4.3; P = .02). Excision of the entire meshwork, between stents, dropped IOP to 6.3 +/- 3.2 mm Hg, indicating some residual meshwork or canal resistance remained even after placement of three stents. CONCLUSIONS: Bypass of the trabecular meshwork lowers IOP in cultured human anterior segments. One stent produced the greatest change in pressure. The sequential addition of more stents further lowered pressure in seven of nine eyes. This technique holds promise as a new clinical surgery for glaucoma.

Anterior Eye Segment↗