Aqueous humor dynamics with a passive valve glaucoma drainage device post-implantation

The Boston Keratoprosthesis: Highs and Lows of Intraocular Pressure and Outcomes

To evaluate the efficacy and safety of implantation of a second glaucoma drainage device for eyes that have failed a primary device. Medical records of patients receiving a primary glaucoma drainage device at Bascom Palmer Eye Institute from January 1987 to October 1998 were reviewed, of which 18 eyes of 18 patients were studied. Patients failing a primary glaucoma drainage procedure and receiving a second glaucoma drainage device were included in this study. The second eye in the same patient was excluded if a second drainage implant was required. All patients received a second device in a standardized fashion with the drainage tube inserted in the anterior chamber. Main outcome measures included: visual acuity, intraocular pressure (IOP), antiglaucomatous medication, length of follow up, and surface area of glaucoma drainage device. Success was defined as an IOP less than or equal to 21 mm Hg with or without medications, and at least a 20% reduction in IOP, without the need for additional glaucoma procedures. The mean postoperative IOP (19.6 +/- 9.4 mm Hg; range, 8-50 mm Hg) was significantly (P = 0.006) lower than the mean preoperative IOP (29.5 +/- 8.1 mm Hg; range, 20-52 mm Hg) at last follow up (mean 19.6 +/- 13.6 months; range, 6-47 months). The mean number of postoperative antiglaucomatous medications (2.2 +/- 1.2; range 0-4) was statistically similar (P = 0.2) to mean preoperative number of antiglaucomatous medications (2.6 +/- 1.2, range 1-4). Using Kaplan-Meier estimates, successful IOP reduction was observed in 89%, 83%, 63%, and 37% of eyes at 6 months, 1, 2, and 3 years, respectively. Four patients (21%) had a decline in visual acuity. Implantation of secondary glaucoma drainage devices may be useful in eyes that have failed primary devices.

To assess and compare the outcomes of trabeculectomy with and without antimetabolites (AMs) and glaucoma drainage devices (GDDs) in the management of elevated intraocular pressure (IOP) after penetrating keratoplasty (PK). Data of 84 eyes of 81 patients who underwent trabeculectomy (12 eyes without an AM and 42 eyes with an AM) or GDD implantation (30 eyes) after PK were reviewed retrospectively. The main outcome measures were IOP control, corneal graft survival, and postoperative ocular complications. At the final visit, IOP success (<22 mm Hg) was 58.3% in trabeculectomy alone, 64.3% in trabeculectomy with an AM (TrabAM), and 86.7% in GDD groups (P = 0.047). The median time from surgery to IOP failure was 1 month after trabeculectomy alone, 13 months after TrabAM, and 20 months after GDD implantation (P = 0.042). The cumulative probability of IOP success rates at 1 and 3 years postoperatively was as follows: 66.7% and 57.1% in trabeculectomy alone, 80.6% and 64.8% in TrabAM, and 92.3% and 84.6 in GDD groups (P = 0.063). The cumulative probability of corneal graft survival rates at 1 and 3 years postoperatively was as follows: 70.0% and 60.0% in trabeculectomy alone, 76.7% and 67.7% in TrabAM, and 65.8% and 52.6% in GDD groups (P = 0.549). GDDs are more successful than trabeculectomy in controlling IOP in eyes that have undergone PK, but they tend to have low corneal graft survival rates. Trabeculectomy without an AM has limited success and may be considered in a limited number of patients with a low risk for bleb failure.

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 hypertensive phase is significantly attenuated compared with the commercial device. Fibrotic encapsulation of the device is also minimized with the biodegradable valve in vivo.

Introduction : Glaucoma drainage devices (GDDs) implantation are frequently indicated for refractory glaucoma. The preferable anterior chamber may be inaccessible for patients with anterior chamber abnormalities.&#x0D; Case Illustration : A 6-year-old boy presented with high intraocular pressure (IOP) on the right eye (RE) four months before admission. Cataract surgery on both eye was done four years prior, due to congenital cataract. On examination, the visual acuity of the RE was hand movement with IOP 61mmHg with medications. Anterior chamber was shallow, posterior synechiae was found and posterior segment was hard to be evaluated. The fellow eye was nonfunctional with IOP 31mmHg. Pars plana vitrectomy (PPV) was performed followed by implantation of GDD (Virna Glaucoma Implant) with posterior chamber sulcus tube placement without adding a new incision. Post-operatively, IOP was 3mmHg and choroidal detachment was found. With steroid medication, satisfactory IOP control was achieved within three weeks of follow-up. Visual acuity of RE was improved to 0.5/60.&#x0D; Discussion : In eyes with shallow anterior segments, tube placed in the anterior chamber may increase the risk of corneal endothelial injury. Placement of the silicone tube in the posterior chamber sulcus is an effective alternative technique. Although it is relatively safe in experienced hands, vitrectomy and insertion of the tube into the posterior segment carries significant risks, including choroidal detachment. Careful monitoring and management is needed to control IOP and maintain vision.&#x0D; Conclusion : Combined GDD implantation and PPV may be considered for refractory aphakic glaucoma, showing favorable outcomes with a relatively safe procedure.

Lentiviral Vector-Mediated Expression of Exoenzyme C3 Transferase Lowers Intraocular Pressure in Monkeys.

Implantation of glaucoma drainage devices has become a standard procedure in various forms of intractable glaucoma. Indications include extensive conjunctival scanning at the upper limbal area, neovascular glaucoma (in addition to pars plana vitrectomy and endolasercoagulation), and secondary glaucoma due to uveitis or trauma. Implanting a glaucoma drainage device is an alternative to trabeculectomy with antimetabolites in young patients in whom delayed complications such as bleb-related endophthalmitis are more likely to occur. Intermediate-term success rates ranging from 70% to 90% are encouraging; however, long-term rates are substantially lower (< or = 50%). Major complications after glaucoma drainage device implantation include hypotony with suprachoroidal hemorrhage and shallowing of the anterior chamber, tube obstruction by fibrin clot, and long-term failure caused by bleb fibrosis. Various glaucoma drainage devices are commercially available; however, none of the designs has proved to be superior to the others.

Background: Aqueous humor outflow resistance in the trabecular meshwork (TM), juxtacanalicular connective tissue (JCT), and Schlemm’s canal (SC) endothelium of the conventional outflow pathway actively contribute to intraocular pressure (IOP) regulation. Outflow resistance is actively affected by the dynamic outflow pressure gradient across the TM, JCT, and SC inner wall tissues. The resistance effect implies the presence of a fluid–structure interaction (FSI) coupling between the outflow tissues and the aqueous humor. However, the biomechanical interactions between viscoelastic outflow tissues and aqueous humor dynamics are largely unknown. Methods: A 3D microstructural finite element (FE) model of a healthy human eye TM/JCT/SC complex was constructed with elastic and viscoelastic material properties for the bulk extracellular matrix and embedded elastic cable elements. The FE models were subjected to both idealized and a physiologic IOP load boundary using the FSI method. Results: The elastic material model for both the idealized and physiologic IOP load boundary at equal IOPs showed similar stresses and strains in the outflow tissues as well as pressure in the aqueous humor. However, outflow tissues with viscoelastic material properties were sensitive to the IOP load rate, resulting in different mechanical and hydrodynamic responses in the tissues and aqueous humor. Conclusions: Transient IOP fluctuations may cause a relatively large IOP difference of ~20 mmHg in a very short time frame of ~0.1 s, resulting in a rate stiffening in the outflow tissues. Rate stiffening reduces strains and causes a rate-dependent pressure gradient across the outflow tissues. Thus, the results suggest it is necessary to use a viscoelastic material model in outflow tissues that includes the important role of IOP load rate.

To evaluate the safety and effectiveness of the Ahmed ClearPath® (ACP) 250 mm2 glaucoma drainage device (GDD) in managing refractory primary open-angle glaucoma (POAG). This was a retrospective case series focused on adult patients diagnosed with severe POAG who underwent implantation of an ACP GDD. Over a 36-month follow-up period, data on intraocular pressure (IOP), the number of glaucoma medications, and complications were recorded. The primary objectives were to assess the reductions from baseline in both IOP and medication usage, through 36 months. Secondary objectives included the proportion of eyes achieving an IOP reduction of ≥ 20% from baseline at 36 months. Intraoperative and postoperative complications were also assessed. Twelve eyes from 11 patients (mean age: 71.3 ± 14.1 years) met the inclusion criteria and were included in the study. All patients had severe POAG (n=11), with the majority being Caucasian (n=8) and female (n=10). The mean (standard deviation) IOP and number of glaucoma medications at baseline were 29 (7.6) mmHg and 3 (0.9), respectively. At 36 months, mean IOP was reduced to 10.6 (5.5) mmHg (-61.8%; p= 0.0008) and mean number of medications was reduced to 0.9 (0.9) (-71.4%; p=0.0005), with 88.9% of eyes achieving an IOP reduction by ≥20%. No vision threatening complications were observed. To our knowledge this is the first study to report 36-month outcomes of the novel ACP device in the treatment of refractory POAG. The safety profile and efficacy of the ACP was found to be comparable to that of other commonly utilized GDD models.

Ultrasound evaluation of glaucoma drainage devices in children

Simultaneous pars plana vitrectomy and glaucoma drainage device implant

Excessive fibrosis is the topmost factor for the defeat of surgical glaucoma drainage device (GDD) implantation. Adjuvant drug approaches are promising to help reduce the scar formation and excessive fibrosis. Opal shale (OS), as a natural state and noncrystalline silica substance with poriferous nature and strong adsorbability, is highly likely to undertake drug loading and delivery. Here, we employed OS microparticles (MPs) by ultrasound and centrifugation and presented an innovative and improved GDD coated with OS MPs, which were loaded with mitomycin C (MMC). MMC-loaded OS MPs were physically absorbed on the Ahmed glaucoma valve surface through OS' adsorbability. About 5.51 μg of MMC was loaded on the modified Ahmed glaucoma valve and can be released for 18 days in vitro. MMC-loaded OS MPs inhibited fibroblast proliferation and showed low toxicity to primary Tenon's fibroblasts. The ameliorated drainage device was well tolerated and effective in reducing the fibrous reaction in vivo. Hence, our study constructed an improved Ahmed glaucoma valve using OS MPs without disturbing aqueous humor drainage pattern over the valve surface. The modified Ahmed glaucoma valve successfully alleviated scar tissue formation after GDD implantation surgery.

We conducted a retrospective review of patients (< 18 years) between 2013 and 2021 to determine risk factors of pediatric patients receiving a glaucoma drainage device (GDD) needing a scleral buckle (SB) and vice versa. The first population underwent an SB placement with no prior GDD. The second underwent a GDD implantation with no prior SB. We analyzed 133 eyes in the SB-first group. The common indications were retinal detachment associated with a syndrome/disease (41.2%), blunt trauma (21%), and non-syndromic pathologic myopia (11%). Twelve eyes (9%) required subsequent GDD implantation with a mean time to reoperation of 19.73 months (median 2.3 months). Eyes with trauma had a 5-fold risk (hazard ratio [HR] 4.81, p = 0.0069) of requiring a subsequent GDD. Each additional glaucoma medication before initial SB surgery increased the risk by 1.81 (p = 0.0096). 135 eyes were in the GDD-first group. Four eyes (3%) required a subsequent SB. The mean time to reoperation was 17 months (median 9.2 months). There was a statistically significant association with trauma (HR 12.3, p = 0.0341) only. Pediatric eyes with a history of trauma and/or multiple glaucoma medications before intervention have a high risk of requiring both an SB and GDD.

Re: Pakravan et al.: Effect of early treatment with aqueous suppressants on Ahmed glaucoma valve implantation outcomes (Ophthalmology 2014;121:1693-8)

Effectiveness of Trabeculectomy and Tube Shunt with versus without Concurrent Phacoemulsification: Intelligent Research in Sight Registry Longitudinal Analysis