A New Adjustable Glaucoma Drainage Device (original) (raw)
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In Vivo Testing of a Novel Adjustable Glaucoma Drainage Device
Investigative Ophthalmology & Visual Science, 2014
PURPOSE. We report on the in vivo testing of a novel noninvasively adjustable glaucoma drainage device (AGDD), which features an adjustable outflow resistance, and assess the safety and efficiency of this implant.
In Vitro and In Vivo Flow Characteristics of Glaucoma Drainage Implants
Ophthalmology, 1995
To determine pressure-flow characteristics at physiologic flow rates in vitro and in vivo in rabbits for Ahmed, Baerveldt, Krupin disk, and OptiMed glaucoma implants. The Molteno dual-chamber implant also was evaluated in vivo only. Methods: Five samples of each glaucoma implant were studied. Baerveldt implants were ligated partially for in vitro testing. Opening and closing pressures in air or after immersion in balanced salt solution or plasma were evaluated for the valved devices (Ahmed and Krupin). Pressures were measured in vitro and in vivo in normal rabbits at flow rates preset at between 2 and 25 Ill/minute after the tubes were connected to a closed manometric system. In vivo measurements were made 24 hours after implantation. Resistance to flow was calculated using Poiseuille's equation after at least three separate flow rate readings. Resuns: In air, the Ahmed and Krupin valves had opening pressures of 9.2 ± 3.4 and 7.2 ± 0,6 mmHg and closing pressures of 5.2 ± 0.9 and 3,9 ± 1 mmHg, respectively. Neither opening nor closing pressures could be determined when Ahmed and Krupin valves were immersed. In vitro, the Ahmed and OptiMed devices had higher pressures than did other devices at a 2-lllfminute flow rate of balanced salt solution. During perfusion with plasma, only the OptiMed device maintained higher pressures than with balanced salt. With all devices, pressures fell rapidly to zero after flow was stopped. The OptiMed device demonstrated the highest resistance values. In vivo, the Ahmed device provided pressures of 7.5 ± 0.8 mmHg and the OptiMed device gave pressures of 19.6 ± 5.6 mmHg at a 2-Ill/minute flow rate. After 15 minutes of flow shutdown, the OptiMed implant maintained pressures of 7.1 ± 1.1 mmHg. The Baerveldt (nonligatured), Krupin, and Molteno dualchamber implants had similar resistances and pressures in vivo. Pressures with all devices in vivo fell rapidly to zero after conjunctival wound disruption, Conclusion: Neither the Ahmed nor Krupin devices had demonstrable opening or closing pressures when tested in vitro immersed in balanced salt solution or plasma. With all devices, pressures were higher in vivo than in vitro due to tissue-induced resistance around the explant. Both Ahmed and Krupin valves functioned as flow-restricting devices at the flow rates studied, but did not close after initial perfusion with fluid.
A model for designing intraocular pressure-regulating glaucoma implants
PLOS ONE, 2022
Glaucoma is a group of eye conditions that damage the optic nerve, the health of which is vital for vision. The key risk factor for the development and progression of this disease is increased intraocular pressure (IOP). Implantable glaucoma drainage devices have been developed to divert aqueous humor from the glaucomatous eye as a means of reducing IOP. The artificial drainage pathway created by these devices drives the fluid into a filtering bleb. The long-term success of filtration surgery is dictated by the proper functioning of the bleb and overlying Tenon's and conjunctival tissue. To better understand the influence of the health condition of these tissues on IOP, we have developed a mathematical model of fluid production in the eye, its removal from the anterior chamber by a particular glaucoma implant-the PRESERFLO ® MicroShunt-, drainage into the bleb and absorption by the subconjunctival vasculature. The mathematical model was numerically solved by commercial FEM package COMSOL. Our numerical results of IOP for different postoperative conditions are consistent with the available evidence on IOP outcomes after the implantation of this device. To obtain insight into the adjustments in the implant's hydrodynamic resistance that are required for IOP control when hypotony or bleb scarring due to tissue fibrosis take place, we have simulated the flow through a microshunt with an adjustable lumen diameter. Our findings show that increasing the hydrodynamic resistance of the microshunt by reducing the lumen diameter, can effectively help to prevent hypotony. However, decreasing the hydrodynamic resistance of the implant will not sufficiently decrease the IOP to acceptable levels when the bleb is encapsulated due to tissue fibrosis. Therefore, to effectively reduce IOP, the adjustable glaucoma implant should be combined with a means of reducing fibrosis. The results reported herein may provide guidelines to support the design of future glaucoma implants with adjustable hydrodynamic resistances.
The Choice of Drainage Device in Complicated Glaucomas: Comparing Ahmed and Baerveldt Implants
In Vivo
Background/Aim: Glaucoma is a chronic and progressive optic neuropathy which leads to deterioration of visual function. It is estimated to be the second leading cause of severe vision loss and blindness worldwide. Failure of antiglaucoma medication to sufficiently reduce intraocular pressure (IOP) and poor compliance with medication are indications for glaucoma surgery, for example using glaucoma drainage devices. Our aim was to compare the surgical outcomes following the implantation of Ahmed FP7 and Baerveldt 350 drainage devices. Patients and Methods: Five hundred and fiftytwo patients with primary or secondary glaucoma were enrolled in the study. All patients had a history of failed trabeculectomy or other intraocular surgery, and IOP ≥18 mm Hg. The implantation of Ahmed (266 patients) or Baerveldt (286 patients) devices was randomly performed in the patients, who were subsequently examined for a period of 5 years. Follow-up visits were scheduled 1 day; 1 week; 1, 3 and 6 months; and 1, 1.5, 2, 3, 4 and 5 years postoperatively. Results: Significant reduction of IOP was achieved in both groups. Ahmed valve (28.3±9.3, 13.4±6.9, 14.2±6 and 12.7±4.5 mmHg at baseline, 1, 3, and 5 years postoperatively, respectively) resulted in significantly greater IOP reduction compared to Baerveldt implant (29.6±10.1, 15.4±5.5, 14.5±5.5 and 14.7±4.4 mmHg at baseline, 1, 3, and 5 years postoperatively, respectively). A significantly lower number of medications was required in the Ahmed group in comparison to the Baerveldt one (Ahmed group: 1.5±1.4, 1.4±1.5 and 1.8±1.5; Baerveldt group: 1.9±1.3, 1.9±1.3 and 2.2±1.4, respectively). The incidence of treatment failure and the rate of glaucoma reoperation were significantly higher in the Baerveldt group (40%) compared to the Ahmed group (17%). Conclusion: Ahmed drainage implantation seemed to outclass that using the Baerveldt device in our study, in terms of efficacy and success rate.
A Short Survey on Currently Used Experimental Setups for Testing Glaucoma Drainage Devices
Commonly used glaucoma drainage devices have many disadvantageouscircumstancesespecially in postoperative period such as hypotony, flammation, etc. There are great efforts to overcome these problems in literature. Researchershave investigated glaucoma drainage devicesby in-vivo, ex-vivo and in-vitro experimental setups and tried to overcome their disadvantages. In this study,one branch of them, in-vitro experimental setups currently usedin testing of glaucoma drainage devices are surveyed.
Advanced healthcare materials, 2014
Glaucoma drainage device (GDD) implantation is an effective method of lowering the intraocular pressure (IOP). Commonly used GDDs can be classified into nonvalved and valved. Although a stable IOP is critical, currently available devices often cause extreme IOP fluctuations: nonvalved GDDs suffer from a risk of hypotony (IOP<5 mmHg), whereas valved GDDs have a higher risk ocular hypertensive (IOP>22 mmHg). It is hypothesized that a GDD with a valve designed to open around the time of onset of the hypertensive phase, would minimize IOP fluctuation. Accordingly, a valve fabricated from a biodegradable polymer poly(L-lactide-co-ϵ-caprolactone) (PLC 70/30) is evaluated in vitro and in vivo. The pressure response is compared with its non-degradable counterpart in in vitro studies of IOP. It is also established that in vitro, the biodegradability of the valve is programmed to occur over 12 weeks. In vivo, a steady and low IOP is achieved with the biodegradable valve and the hyperten...
Current Directions in Biomedical Engineering, 2021
Implant devices for micro invasive glaucoma surgery (MIGS) are gaining increasing acceptance in clinical ophthalmic use. The implant requirements are defined in international standards, such as ANSI Z80.27-2014 and the 2015 Guidance for Industry and Food and Drug Administration Staff “Premarket Studies of Implantable Minimally Invasive Glaucoma Surgical (MIGS) Devices”. The exact fluid-mechanical characterization represents a crucial part of the development and approval of innovative implant devices for MIGS. The current work describes the development and preliminary validation of a versatile test facility for pivotal characterization of glaucoma drainage devices. The test setup enables a pressurization of test specimens by means of two water columns. For measurement of pressure and volume flow, a pressure transducer and a total of three liquid flow meters were implemented into the test setup. Validation was conducted by experimental pressureflow characterization of standardized tub...
Artificial drainage devices for glaucoma surgery: an overview
Nepalese journal of ophthalmology : a biannual peer-reviewed academic journal of the Nepal Ophthalmic Society : NEPJOPH
Artificial drainage devices (ADD) create an alternative pathway for aqueous drainage from the anterior chamber of an eye through a tube to the subconjunctival bleb connected to an equatorial plate under the conjunctiva. The ADDs, both valved and non-valved, are available for end stage or refractory glaucoma. Currently, some of these devices, particularly the Express shunt, are recommended for the primary treatment of glaucoma. In this article, we highlight various ADDs, their indications and contraindications, surgical techniques and associated complications.
IEEE Transactions on Biomedical Engineering, 2005
We report on modeling and bench test results targeted at better understanding of valved glaucoma drainage devices (GDDs), a common current surgical treatment for glaucoma. A simple equivalent circuit is described to model fluid mechanical behavior of the aqueous humor in an eye with glaucoma, both before and after implantation of a valved GDD. Finite element method simulations (FEM), based on the lubrication-von Kármán model, are then performed to analyze the valve&amp;amp;amp;amp;amp;amp;amp;#39;s mechanical and fluidic performance. Using nanoporous membranes to mimic the in vivo fibrous capsule, we have developed a microfluidic bench test to simulate the aqueous humor flow and the post-implantation fibrous tissue encapsulation around the GDD back plate. Our numerical and bench test results show that, contrary to the prevailing belief, the valve significantly contributes to the total pressure drop even after fibrous capsule formation. Furthermore, we show that bypassing the valve through a simple polyimide tube insertion will dramatically lower the intraocular pressure (IOP) after fibrous capsule formation. This may offer a new treatment option in some patients with advanced glaucoma.