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Comparison of two prototypes of a magnetically adjustable glaucoma implant in rabbits.

ABSTRACT: Glaucoma drainage devices are used in surgical glaucoma therapy. Success of controlling the intraocular pressure is limited due to fibrous implant encapsulation and fibrin coating on the implant which lead to drainage obstructions. An innovative implant with a magnetically adjustable valve was developed. The valve opening of the implant should eliminate inflammatory products from the outflow area and affect fibrous tissue formation to achieve a sufficient long-term aqueous humour outflow. Lifting of this valve should disturb cell adhesion by exerting mechanical forces. Before testing this hypothesis, the flow characteristics of glaucoma drainage devices, especially the outflow resistance by regular IOP, should be considered in a pilot study, as they are important in preventing too low postoperative intraocular pressure known as ocular hypotony. Therefore, two prototypes of the innovative implant differing in their valve area design were examined regarding their flow characteristics in a limited animal experiment lasting two weeks. Ten healthy New Zealand White rabbits were divided into two groups (A & B) with different implanted prototypes. Daily, tonometry and direct ophthalmoscopy were performed to assess the intraocular pressure and the inflammatory reaction of the eye. After two weeks, the rabbits were euthanised to evaluate the initially histological inflammatory reaction to the implant. In group A, one case of hypotony emerged. When considering the entire observation period, a highly statistically significant difference between the intraocular pressure in the operated eye and that in the control eye was detected in group A (p < 0.0001) in contrast to group B (p = 0.0063). The postoperative inflammatory signs decreased within two weeks. Histologically, a typical but low level foreign body reaction with macrophages and lymphocytes as well as mild to moderate fibrosis was seen after the short experimental period. Based on our tonometric results, prototype B seems to be the system of choice for further research assessing its long-term function and biocompatibility.

SUBMITTER: Schwerk B

PROVIDER: S-EPMC6459522 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Comparison of two prototypes of a magnetically adjustable glaucoma implant in rabbits.

Schwerk Birthe B Harder Lisa L Windhövel Claudia C Hewicker-Trautwein Marion M Wagner Anna A Bach Jan-Peter JP Voigt Lena Carolin LC Hinze Ulf U Chichkov Boris B Haferkamp Heinz H Lubatschowski Holger H Nikolic Stephan S Nolte Ingo I

PloS one 20190411 4

Glaucoma drainage devices are used in surgical glaucoma therapy. Success of controlling the intraocular pressure is limited due to fibrous implant encapsulation and fibrin coating on the implant which lead to drainage obstructions. An innovative implant with a magnetically adjustable valve was developed. The valve opening of the implant should eliminate inflammatory products from the outflow area and affect fibrous tissue formation to achieve a sufficient long-term aqueous humour outflow. Liftin ...[more]

PMID: 30973952

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Project description:PurposeIn eyes with a prior failed aqueous shunt (or "tube") requiring additional intraocular pressure (IOP) control, options include angle surgery, cyclodestruction, second tube, tube revision, or tube exchange. We present a case of a same-quadrant tube exchange of a Baerveldt-250 (BGI-250) to BGI-350.ObservationsThe patient is a 71-year-old African American female with severe-stage primary open angle glaucoma of both eyes, and this case focuses on the right eye. This eye had prior cataract surgery with iStent, prior BGI-250 in the anterior chamber (AC), and prior iStent removal with gonioscopy assisted transluminal trabeculotomy (GATT). The visual acuity (VA) was 20/150, and the IOP was 26 mmHg on 3 IOP-lowering medications. The prior superotemporal BGI-250 had its "wings" on top of the superior and lateral rectus muscles and its tube tip in the AC. The implant was removed in its entirety including the superficial and deep layers of its capsule. The new BGI-350 was stented with a 3-0 polypropylene ripcord, ligated with a 7-0 polyglactin suture, and implanted with its wings under the rectus muscles and the tube tip in the sulcus. For early IOP-lowering prior to ligature dissolution, 2 needle stab fenestrations and an additional 7-0 polyglactin wick was used. The capsule from the prior BGI-250 was used as a patch graft for the new BGI-350. The ligature dissolved at postoperative week (POW) 6. By POW8, the IOP was 18 mmHg on 3 IOP-lowering medications and frequent topical steroid, the AC was quiet, and the ripcord was removed. A slow steroid taper finished at postoperative month (POM) 6. By POM 12, the VA was still at baseline 20/150, and the IOP was 14 mmHg on 3 IOP-lowering medications.Conclusions & importancePatients with a prior failed tube requiring additional IOP-lowering can undergo a same-quadrant tube exchange. BGI-350s may offer more IOP-lowering than BGI-250s, but the IOP-lowering achieved in this patient's case could be attributable to differences in postoperative management in addition to endplate size; longer follow-up is needed. A tube exchange offers the opportunity to reposition the tube tip from the AC to the sulcus and to use the prior tube's capsule as a patch graft for the new tube.

Dataset Information

Comparison of two prototypes of a magnetically adjustable glaucoma implant in rabbits.

Publications

Comparison of two prototypes of a magnetically adjustable glaucoma implant in rabbits.

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