Tissue Response to Implanted Ahmed Glaucoma Valve with Adjunctive Amniotic Membrane in Rabbit Eyes

Lee, Jiwoong; Park, Won Young; Kim, Eun Ah; Yun, Il Han

doi:10.1159/000357097

Cited by 24 publications

(27 citation statements)

References 60 publications

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“…[28] Several novel designs of glaucoma surgical devices aimed at reducing scar formation have been tested, including a MMC-coated valve, Ferrofluid valve, expanded polytetrafluoroethylene enclosed Ahmed, and Ahmed Glaucoma Valve with Adjunctive Amniotic Membrane. [29–32] These modifications and designs have been shown to decrease the amount of fibrosis and scar tissue when compared to conventional glaucoma devices but still resulted in significant capsule formation. [31,32]…”

Section: Discussionmentioning

confidence: 99%

“…[29–32] These modifications and designs have been shown to decrease the amount of fibrosis and scar tissue when compared to conventional glaucoma devices but still resulted in significant capsule formation. [31,32]…”

Section: Discussionmentioning

confidence: 99%

“…In our study, the average capsule thickness under the AGV PF7 plate implant was 89μm, which is comparable with the capsule thickness reported in the literature. [29–32]…”

Section: Discussionmentioning

confidence: 99%

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A novel flexible microfluidic meshwork to reduce fibrosis in glaucoma surgery

et al. 2017

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Purpose/RelevanceFibrosis and hence capsule formation around the glaucoma implants are the main reasons for glaucoma implant failure. To address these issues, we designed a microfluidic meshwork and tested its biocompatibility in a rabbit eye model. The amount of fibrosis elicited by the microfluidic meshwork was compared to the amount elicited by the plate of conventional glaucoma drainage device.MethodsSix eyes from 3 New Zealand albino rabbits were randomized to receive either the novel microfluidic meshwork or a plate of Ahmed glaucoma valve model PF7 (AGV PF7). The flexible microfluidic implant was made from negative photoresist SU-8 by using micro-fabrication techniques. The overall size of the meshwork was 7 mm × 7 mm with a grid period of 100 μm. Both implants were placed in the subtenon space at the supratemporal quadrant in a standard fashion. There was no communication between the implants and the anterior chamber via a tube. All animal eyes were examined for signs of infection and implant erosion on days 1, 3, 7, and 14 and then monthly. Exenterations were performed in which the entire orbital contents were removed at 3 months. Histology slides of the implant and the surrounding tissues were prepared and stained with hematoxylin-eosin. Thickness of the fibrous capsules beneath the implants were measured and compared with paired student’s t-test between the two groups.ResultsThe gross histological sections showed that nearly no capsule formed around the microfluidic meshwork in contrast to the thick capsule formed around the plate of AGV PF7. Thickness of the fibrotic capsules beneath the AGV PF7 plate from the 3 rabbit eyes was 90μm, 82μm, and 95 μm, respectively. The thickness at the bottom of fibrotic capsules around the new microfluidic implant were 1μm, 2μm, and 1μm, respectively. The difference in thickness of capsule between the two groups was significant (P = 0.002). No complications were noticed in the 6 eyes, and both implants were tolerated well by all rabbits.ConclusionThe microfluidic meshwork elicited minimal fibrosis and capsule formation after 3-months implantation in a rabbit model. This provides promising evidence to aid in future development of a new glaucoma drainage implant that will elicit minimal scar formation and provide better long-term surgical outcomes.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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A novel flexible microfluidic meshwork to reduce fibrosis in glaucoma surgery

et al. 2017

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“…Following AGV implantation, a fibrotic response encapsulates the plate of the drainage device, leading to increased aqueous outflow resistance [19, 20]. Histopathological analysis from the inner layer of the encapsulated bleb showed transformation of fibroblasts into myofibroblasts in the collagen fibers.…”

Section: Discussionmentioning

confidence: 99%

Ahmed Glaucoma Valve Implantation for Refractory Glaucoma in a Tertiary Hospital in Brazil

Abe

Tavares

Schimiti

et al. 2015

Journal of Ophthalmology

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Purpose. To evaluate the efficacy of Ahmed Glaucoma Valve (AGV) implantation in patients with refractory glaucoma in a tertiary hospital in Brazil. Methods. Retrospective case series of patients who underwent AGV implantation. Primary outcome was to assess the rate of failure, which was defined as intraocular pressure (IOP) in two consecutive visits greater than 18 or lower than 5 mmHg (criterion 1) or IOP greater than 15 or lower than 5 mmHg (criterion 2). The secondary outcome was to investigate risk factors for failure. Results. 112 eyes from 108 patients underwent AGV implantation between 2000 and 2012. Mean follow-up time was 2.54 (±1.52) years. Kaplan-Meier survival analysis showed cumulative probabilities of success of 80.3%, 68.2%, and 47.3% at 1, 3, and 5 years using 18 mmHg as endpoint. When adopting 15 mmHg as endpoint, cumulative success rates were 80.3%, 60.7%, and 27.3% at 1, 3, and 5 years, respectively. Multivariate analysis with generalized estimating equations revealed that African American ancestry and early hypertensive phase were risk factors for failure (P = 0.001 and P = 0.002, resp.). Conclusion. A success rate of approximately 50% was obtained 5 years after the implantation of an AGV. African American ancestry and early hypertensive phase were associated with increased risk of failure.

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“…[74][75][76] Recently, the addition of dried human amniotic membrane on top of Ahmed valves in rabbits has gained thinner and looser blebs. 77 Contrasting reports on the efficacy of antimetabolites are also present in veterinary literature. Tinsley and colleagues 10,78 have reported in vitro (MMC and 5-FU) and in vivo (MMC) inhibition of fibroblast proliferation, with thinner capsules and IOP control in the short term.…”

Section: Filtering and End-stage Glaucoma Proceduresmentioning

confidence: 99%