Yuan Fan, Schieber Andrew T, Camras Lucinda J, Harasymowycz Paul J, Herndon Leon W, Allingham R Rand
Departments of *Biomedical Engineering †Ophthalmology, Duke University, Durham, NC ‡Ivantis Inc., Irvine, CA §Department of Ophthalmology, Maisonneuve-Rosemont Hospital, Montreal, QC, Canada.
J Glaucoma. 2016 Apr;25(4):355-64. doi: 10.1097/IJG.0000000000000248.
To mathematically model the conventional aqueous humor outflow system with trabecular meshwork (TM) bypass and Schlemm canal (SC) dilation.
The SC was modeled as a rectangular channel with the TM modeled as a permeable membrane. The collector channels (CCs) were modeled as fluid sinks distributed along the outer wall of SC. Two different implants were investigated in this study. The Hydrus Microstent (scaffold) was modeled with a TM bypass and a dilated region in SC that was 7 or 15 mm long and approximately 5-fold larger than the normal height of SC (h0). The iStent trabecular microbypass was modeled with a similar structure except that the dilated region in SC was 1 mm long and 25% larger than h0.
Creation of a TM bypass structure would increase the pressure in the surrounding regions inside the SC and make it close to the intraocular pressure. SC dilation would increase the pressure more uniformly in the dilated region. The pressure increase led to higher flow rates in SC and CCs, and subsequently increased outflow facility (C). If CCs were uniformly distributed, the increase in C was the smallest after implantation of 1 microbypass, compared with that after implantation of 2 microbypasses or 1 scaffold. If CCs were nonuniformly distributed, the magnitude of increase in C was sensitive to the location of implant, and the sensitivity was higher for the microbypass than the scaffold.
The study showed that creation of TM bypass and SC dilation significantly increased outflow facility, and the amount of increase correlated with the length of dilated regions in SC.
对具有小梁网（TM）旁路和施莱姆管（SC）扩张的传统房水流出系统进行数学建模。
将SC建模为矩形通道，将TM建模为可渗透膜。收集通道（CCs）建模为沿SC外壁分布的流体汇。本研究中研究了两种不同的植入物。Hydrus微支架（支架）建模为具有TM旁路和SC中7或15毫米长且比SC正常高度（h0）大约5倍大的扩张区域。iStent小梁微旁路建模为具有类似结构，不同之处在于SC中的扩张区域为1毫米长且比h0大25%。
创建TM旁路结构会增加SC内部周围区域的压力并使其接近眼内压。SC扩张会在扩张区域更均匀地增加压力。压力增加导致SC和CCs中的流速更高，并随后增加流出易度（C）。如果CCs均匀分布，与植入2个微旁路或1个支架后相比，植入1个微旁路后C的增加最小。如果CCs分布不均匀，C增加的幅度对植入物的位置敏感，并且微旁路的敏感性高于支架。
该研究表明，创建TM旁路和SC扩张显著增加了流出易度，并且增加量与SC中扩张区域的长度相关。
