A Model to Measure Fluid Outflow in Rabbit Capsules Post Glaucoma Implant Surgery

Nguyen, Dan Q; Ross, Craig; Li, Yu Qin; Pandav, Surinder Singh; Gardiner, Bruce S.; Smith, David W.; How, Alicia C.; Crowston, Jonathan G; Coote, Michael

doi:10.1167/iovs.12-10438

Cited by 12 publications

(22 citation statements)

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“…To this end, we have developed methods to measure capsular porosity, which detailed engineering modeling previously identified as the most important characteristic for success. 4,6 We have used GDDs as the preferred method of creating outflow and drainage in an animal model. [9][10][11] Although we have an imperative to limit the use of experimental animals, no method exists to emulate the complex cellular and extracellular dynamics of the capsular development and changes over time in response to various stresses other than the live animal model.…”

Section: Discussionmentioning

confidence: 99%

“…This model further predicts that capsular porosity is the key measurable variable of glaucoma filtration surgery. In a previous study, 6 our group described a surgical model for isolating and accurately measuring this variable. Practical limitations and technical challenges in this surgical model provoked a re-engineering of the experimental system using a design, test, and redesign strategy.…”

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confidence: 99%

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Determination of Bleb Capsule Porosity With an Experimental Glaucoma Drainage Device and Measurement System

Ross

Pandav

et al. 2015

JAMA Ophthalmol

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IMPORTANCE Control of intraocular pressure after implantation of a glaucoma drainage device (GDD) depends on the porosity of the capsule that forms around the plate of the GDD.OBJECTIVE To compare capsular porosity after insertion of 2 different GDDs using a novel implant and measurement system. DESIGN, SETTING, AND SUBJECTSWe performed an experimental interventional study at an eye research facility in a tertiary eye care center. Testing was performed on 22 adult New Zealand white rabbits that received the experimental GDD or an existing GDD.INTERVENTIONS A new experimental GDD, the Center for Eye Research Australia (CERA) implant, was created using computer-aided design and a 3-dimensional printer. The CERA GDDs were implanted in the eyes of rabbits randomized into 1 of the following 3 groups: with no connection to the anterior chamber (n = 7), with connection to the anterior chamber for 1 week (n = 5), and with connection to the anterior chamber for 4 weeks (n = 5). In a control group (n = 5), a pediatric GDD was implanted without connection to the anterior chamber. We measured the capsular porosity using a pressure-gated picoliter pump at a driving pressure of 12 mm Hg. The animals were killed humanely for histologic study. MAIN OUTCOMES AND MEASURESPorosity of the fibrous capsule around the implant. RESULTSWe found no difference in mean (SEM) capsular porosity between the CERA (3.39 [0.76; 95% CI, 1.43-5.48] μL/min) and pediatric (4.52 [0.52; 95% CI, 3.19-5.95] μL/min) GDDs (P = .28, unpaired t test) at 4 weeks without aqueous exposure. Mean (SEM) capsular porosity of CERA GDDs connected to the anterior chamber at 1 week was 2.46 (0.36; 95% CI, 1.55-3.44) μL/min but decreased to 0.67 (0.07; 95% CI, 0.49-0.86) μL/min at 4 weeks (P = .001, unpaired t test). CONCLUSIONS AND RELEVANCEOur experimental method permits direct measurement of capsular porosity of an in situ GDD. In a comparison between an experimental (CERA) and an existing GDD, no differences were identified in capsular porosity or histologic reaction between the implants. These results suggest that the CERA GDD model can be used to test key components of glaucoma surgery and implant design.

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Section: Discussionmentioning

confidence: 99%

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Determination of Bleb Capsule Porosity With an Experimental Glaucoma Drainage Device and Measurement System

Ross

Pandav

et al. 2015

JAMA Ophthalmol

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“…1112 Briefly, an experimental glaucoma drainage device (“CERA GDD”) was implanted in one eye under general anesthesia. The right eye had a limbal conjunctival incision made in the superotemporal quadrant, and the implant was placed and secured there.…”

Section: Methodsmentioning

confidence: 99%

“…Using this model, porosity of the bleb capsule has been studied in the New Zealand White (NZW) rabbit model. 1112 In short, all NZW rabbits had thick capsules with very low porosity at 4 weeks when the implant had been connected to the anterior chamber and the plate had been bathed in aqueous. Histologically, bleb capsules have been reported to have marked subconjunctival/bleb capsule condensation of collagen which is (relatively) impervious.…”

Section: Introductionmentioning

confidence: 99%

Porosity of Bleb Capsule declines rapidly with Fluid Challenge

Pandav

Ross

Thattaruthody

et al. 2016

Journal of Current Glaucoma Practice

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IntroductionThe porosity of the fibrous capsule around a glaucoma drainage device (GDD) may be the most important functional attribute. The factors that determine capsular porosity are not well understood. Failed GDD surgeries are usually associated with thick impervious capsules and components of aqueous have been implicated in this process.PurposeIn this study, we interrogated the effect of passage of nonaqueous fluid on capsular porosity in mature (but aqueous naïve) blebs in a previously reported GDD model (the “Center for Eye Research Australia Implant”).Materials and methodsThe study was performed at two centers using 17 New Zealand White (NZW) rabbits. An experimental GDD was implanted into the subconjunctival space but without connection to the anterior chamber. After 28 days, balanced salt solution (BSS) was passed through the implant for 30 to 40 minutes at 12 mm Hg. Capsular porosity was measured as flow (μL/min) at a constant pressure. Porosity of the capsule was retested at 3 and 6 days.ResultsThere was a marked reduction in capsular porosity within 3 days of exposure to BSS (fluid challenge). Even though the baseline porosity was significantly different in the two groups (3.00 ± 0.5 μL/min and 29.67 ± 12.12 μL/min, p < 0.001), the effect of passage of BSS was similar. Capsular porosity fell by approximately 80% in both groups from baseline after single BSS challenge. Capsular thickness was significantly less in Advanced Eye Center (AEC) rabbits at baseline. There was no change in the capsular thickness before and after single fluid challenge.ConclusionPassage of BSS at physiological pressures for under 40 minutes caused marked reduction in the porosity of the fibrous capsule within 3 days. This was not associated with any significant thickening of the fibrous capsule within this time frame.How to cite this articlePandav SS, Ross CM, Thattaruthody F, Nada R, Singh N, Gautam N, Beirne S, Wallace GG, Sherwood MB, Crowston JG, Coote M. Porosity of Bleb Capsule declines rapidly with Fluid Challenge. J Curr Glaucoma Pract 2016;10(3):91-96.

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“…5 We took an existing implant, a pediatric Molteno implant, which feels rather like it has been designed for New Zealand white rabbits, although Tony Molteno denies he treats New Zealand rabbits with it! We implanted it in one eye and we tested the outflow facility by direct cannulation of the tube.…”

Section: New Endpoints For Glaucoma Surgerymentioning

confidence: 99%