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Teruhiko Hamanaka, Shinki Chin, Yasuhiro Shinmei, Nobuo Ishida, Toshio Kumasaka; Behavior of Schlemm’s canal endothelium after canal surgery
-A new concept of trans-Schlemm’s canal endothelial pressure-. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3748.
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© ARVO (1962-2015); The Authors (2016-present)
Minimally invasive glaucoma surgery (MIGS) has become widely used as a primary glaucoma surgery. Among various types of MIGS, canal surgeries (CASs) such as trabecutome, trabeculotomy ab interno and micro-bypass stent are effective for lowering IOP. The mechanism for lowering IOP in CASs is believed to open S chlemm’s canal (SC) into the anterior chamber by eliminating the most resistant part of corneoscleral meshwork and juxta-canalicular meshwork. If so, IOP could be expected to decrease to the level of aqueous vein pressure, but IOP actually stabilizes around the middle teens. In this study, we investigated the reason for this especially by focusing on the behavior of SC endothelial cells (SCE) using trabeculectomy (TRAB) specimens which include the area of previous CASs
All TRABs were performed after the failure of CASs in open angle glaucoma patients. CASs include trabeculotomy ab externo (TLO-E, 18 eyes), 360 degree TLO (7 eyes). TRAB samples were fixed with formalin or a mixture of glutaraldehyde, embedded in paraffin, and then used for HE stain and immunohistochemical study of CD 34 and thrombomodulin.
In most of the TRAB samples, SCE had completely disappeared from the inner and outer walls of SC except in three samples in 360 TLO and four samples in TLO where linear structures of SCE in the outer wall had locally remained. The remaining SCE had usually formed small vessel like structures around the outer walls of SC. Collector channels were sealed off by SCE in addition to the various amount of scar tissue composed of fibroblasts outside of scarring. Extension of the corneal endothelium were observed in the outer wall of SC in two cases.
SCE had a nature of occluding SC lumen if SC is artificially opened to the anterior chamber, which may be a part of maintaining the blood aqueous barrier function. The reason for the middle teen after CASs may be because aqueous must pass against the SCE lining to the collector channels, which may yield a trans-SCE pressure in addition to the aqueous vein pressure. The main reason for the failure of CASs may be the fibrotic proliferation around the sealing by SCE at the opening of collector channels.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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