Expanded Polytetrafluoroethylene Membrane Alters Tissue Response to Implanted Ahmed Glaucoma Valve

DeCroos, Francis Char; Shadi, Ahmad; Chow, Jessica; Mordes, Daniel; Lee, Maria Regina; Asrani, Sanjay; Allingham, R. Rand; Olbrich, Kevin C.; Klitzman, Bruce

doi:10.1080/02713680902963167

Cited by 20 publications

(25 citation statements)

References 25 publications

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“…Capsules also had more dilated vessels throughout the fibrous capsule. These results were in agreement with previous studies with histopathological findings for a glaucoma drainage device modulated by various adjunctive treatments [28,29,30]. Park et al [28] evaluated the effects in rabbits of topical cyclosporine on the function of filtering blebs after glaucoma drainage implant surgery.…”

Section: Discussionsupporting

confidence: 82%

“…Flow resistance through the implant capsule was significantly lower in the study group [28]. DeCroos et al [29] reported that encapsulating tissue was altered by an expanded polytetrafluoroethylene membrane in AGV surgery, led to greater vascular tissue response and a thinner fibrous capsule compared with a standard glaucoma implant plate. Sahiner et al [30] examined histological findings in rabbits with fibrous capsules around a slow-release antifibrotic drug-coated glaucoma device.…”

Section: Discussionmentioning

confidence: 99%

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

Lee¹,

Park²,

Kim³

et al. 2014

Ophthalmic Res

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Aims: To investigate the histopathology of the fibrous capsule around Ahmed glaucoma valves (AGVs) implanted with adjunctive amniotic membranes in rabbits. Methods: AGV implantation with or without adjunctive amniotic membrane was performed in a single eye of 20 albino rabbits. The upper surface of the AGV body was covered with amniotic membrane in the study group. After 2 months, histology was used to compare the thickness and characteristics of the fibrous capsule, transdifferentiation of myofibroblasts, and density of blood vessels and leukocytes between the study and control groups. Results: The fibrous capsule along the roof of the bleb was composed of compact collagen fibers with minimal vascularization in the control group. In contrast, in the study group, the fibrous capsule was looser and had a more disorganized collagen architecture. The thickness of the fibrous capsule and the myofibroblast layer was significantly thinner in the study group than in the control group (p < 0.001). The number of CD31-positive blood vessels did not differ between the two groups (p = 0.235). CD45-positive inflammatory cells were more frequently observed in the study group than the control group (p = 0.001). The groups did not differ in the thickness of the fibrous capsule or myofibroblast layer, or the density of blood vessels and leukocytes along the floor of the bleb. Conclusions: Adjunctive amniotic membranes could reduce the risk of encapsulation and aqueous outflow resistance by altering the tissue response to implanted AGVs and subsequent formation of a loose thin capsule.

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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

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

Lee¹,

Park²,

Kim³

et al. 2014

Ophthalmic Res

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“…Prior work from our group demonstrated that the PRIME-Ahmed promoted a thinner fibrous capsule and increased vascularity adjacent to the implant when compared to unmodified Ahmed valves implanted in rabbits (46.4 ±10.8 μm versus 94.9 ± 21.2 μm, p < 0.001). 27 A thinner, more vascular capsule may decrease outflow resistance in vivo significantly enough to improve long-term intra-ocular pressure control. However, prior to implantation and in vivo study, it is important to assess how much serial resistance is added by porous membrane enclosure of a GDD outflow tract.…”

Section: Discussionmentioning

confidence: 99%

“…Prior work demonstrated that PRIME-Ahmed implanted into the rabbit eye stimulates a thinner fibrous capsule and increased surrounding vascularity compared to implanted unmodified Ahmed valve. 27 The thinner, more vascular capsule promoted by the PRIME-Ahmed may improve longterm absorption of aqueous fluid through decreased resistance to fluid flow in vivo.…”

Section: Fluid Dynamics Of the Eptfe Modified Ahmed Implantmentioning

confidence: 99%

“…Another fourteen pediatric Ahmed glaucoma Model S3 valve implants (termed porous retrofitted implant with modified enclosure or PRIME-Ahmed) were modified with a porous membrane as described previously (Figure 1). 27 Briefly, the outflow tract was enclosed by a bilayer of ePTFE (TheraCyte, Irvine, California, USA). The pediatric Model S3 was chosen at it allows implantation into a small mammal animal model allowing for in vivo investigations in a prior study.…”

Section: Modified Implant (Prime-ahmed) Creationmentioning

confidence: 99%

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In VitroFluid Dynamics of the Ahmed Glaucoma Valve Modified with Expanded Polytetrafluoroethylene

DeCroos¹,

Mordes²,

Lee³

et al. 2011

Current Eye Research

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A novel bilayered expanded polytetrafluoroethylene glaucoma implant creates a permeable thin capsule independent of aqueous humor exposure

Bicket

Szeto

Roeber

et al. 2020

Bioengineering & Transla Med

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The purpose of these studies was to evaluate clinical, functional, and histopathological features of glaucoma drainage implants (GDIs) fabricated from novel, customtailored expanded polytetrafluoroethylene (ePTFE). Implants of matching footprints were fabricated from silicone (Control) and novel, bilayered ePTFE. ePTFE implants included: (a) one that inflated with aqueous humor (AH) (High), (b) one that inflated with a lower profile (Low), (c) an uninflated implant not connected to the anterior chamber (Flat), and (d) one filled with material that did not allow AH flow (Filled). All implants were placed in adult New Zealand White rabbits and followed over 1-3 months with clinical exams and intraocular pressure. The permeability of tissue capsules surrounding GDIs was assessed using constant-flow perfusion with fluoresceinated saline at physiologic flow rates. After sacrifice, quantitative histopathological measures of capsule thickness were compared among devices, along with qualitative assessment of cellular infiltration and inflammation. Capsular thickness was significantly reduced in blebs over ePTFE (61.4 ± 53 μm) versus silicone implants (193.6 ± 53 μm, p = .0086). AH exposure did not significantly alter capsular thickness, as there was no significant difference between High and Filled (50.9 ± 29, p = .34) implants. Capsules around ePTFE implants demonstrated permeability with steady-state pressure: flow relationships at physiologic flow rates and rapid pressure decay with flow cessation, while pressure in control blebs increased even at low flow rates and showed little decay. Perfused fluorescein dye appeared beyond the plate border only in ePTFE implants. ePTFE implants are associated with thinner, more permeable capsules compared to silicone implants simulating presently used devices.

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Expanded Polytetrafluoroethylene Membrane Alters Tissue Response to Implanted Ahmed Glaucoma Valve

Cited by 20 publications

References 25 publications

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

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

In VitroFluid Dynamics of the Ahmed Glaucoma Valve Modified with Expanded Polytetrafluoroethylene

A novel bilayered expanded polytetrafluoroethylene glaucoma implant creates a permeable thin capsule independent of aqueous humor exposure

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