Silicone Ahmed Glaucoma Valve Research Articles

Safety and Efficacy of Ahmed Valve on Intractable Glaucoma in Saudi Population.

PURPOSE:The study aims to assess the efficacy and safety of Ahmed glaucoma valve implant in eyes with intractable glaucoma and to evaluate the risk factors for failure.METHODS:A retrospective evaluation of 83 patients (117 eyes) with intractable glaucoma who underwent silicone Ahmed glaucoma valve implant was done in a tertiary care center in Riyadh, Saudi Arabia, between January 2014 and December 2016. Complete success was defined as intraocular pressure (IOP) ≤21 mmHg without medication after a minimum follow-up of 6 months.RESULTS:Eighty-three patients (117 eyes) with intractable glaucoma were evaluated. After a mean follow-up duration of 20.8 ± 3.1 (12–24) months, the overall success rate was achieved in 104 eyes (88.9%). Thirty-six eyes (30.8%) had a complete success rate, whereas 68 eyes (58.1%) had a qualified success rate. Thirteen eyes (11.1%) failed to achieve controlled IOP. The postoperative probability to fail was found to be increasing with time from 0.9% (0.9) in the 1st month to 11.1% (9.9) after 1 year. Complications included a hypertensive phase in 25 eyes (21.4%), encapsulation in 10 eyes (8.5%), hyphema in 7 eyes (6%), hypotony in 2 eyes (1.7%), and blood clots in the implanted tube in 2 eyes (1.7%). The presence of hyphema, scleral patch, and coronary heart diseases was found to increase the risk of failure after Ahmed valve implantation (P = 0.006, 0.040, and 0.014, respectively).CONCLUSIONS:Ahmed glaucoma valve implant was safe and effective in treating cases of intractable glaucoma.

Safety and efficacy of paediatric silicone Ahmed glaucoma valve (AGV) in adult eyes with post-VR surgery glaucoma.

To compare the safety and efficacy of the FP8 AGV (paediatric) with the standard FP7 AGV in adult post-vitreoretinal (VR) surgery glaucoma. We included 45 consecutive eyes with post-VR surgery glaucoma implanted with either FP8 (n = 28) or FP7 (n = 17) AGV between 2008 and 2016. The data analysed included visual acuity (VA), intraocular pressure (IOP), complications, interventions, and outcomes. Mean age (p = 0.24), mean baseline VA (p = 0.77), preoperative IOP (p = 0.41), number of antiglaucoma medications (p = 0.92), and previous surgeries (p = 0.16) were comparable in the two groups. The number of eyes with previous belt buckle was significantly higher (p < 0.001) in the FP8 group (17/28) compared with the FP7 group (2/17), indicating space constraint and scarred conjunctiva. The median follow-up (25th, 75th percentile) was 14.7 (9.1, 25.3) months in the FP7 and 9.8 (6.4, 34.7) months in the FP8 groups (p = 0.62). Postoperatively, the median VA (p = 0.24), the mean IOP at final follow-up (p = 0.15), and median number of AGM (p = 0.99) were comparable in both the groups. The median percentage drop in IOP (95% confidence interval) with the FP7 implant was 55% (43.70%) and with FP8 implant was 53.8% (25, 73), (p = 0.20). None in the FP7 group failed, while three eyes in the FP8 group failed. During the study period, two eyes in the FP8 group had tube exposure that was surgically managed. None of the eyes had implant exposure or loss of light perception. Use of the paediatric FP8 AGV in adult post-VR surgery glaucoma eyes with severe conjunctival scarring and limited subconjunctival space resulted in reasonable IOP control compared with the standard FP7 AGV implant. There were no eyes with implant extrusion.

Outcomes of Silicone Ahmed Glaucoma Valve Implantation in Refractory Pediatric Glaucoma

The purpose of this study was to report the outcomes of Silicone Ahmed Glaucoma Valve (AGV) implantation in the management of refractory pediatric glaucoma. Between 2007 and 2015, 76 eyes of 64 children aged 16 years or younger underwent AGV implantation. We included 65 eyes of 53 children with follow up ≥6 months; 24 eyes had primary congenital glaucoma (PCG) and 41 eyes had secondary pediatric glaucoma (SPG). Success was defined as IOP>5 and ≤21 mm Hg with or without topical antiglaucoma medications; considered failure, when repeat glaucoma surgery was need or loss of light perception. Primary outcome measure was success of AGV in refractory pediatric glaucomas and secondary outcome measure was comparison of outcomes in PCG and SPG. The median age at AGV implantation was 3 years (interquartile range, 2, 12), and median follow up was 27 months (15, 39). The overall cumulative success probability was 88% [95% confidence interval (CI), 76%-94%] at 1 year and was maintained up to 4 years. The success probability in PCG was 91% (80.8%-100%), and SPG was 83% (72%-96%) at 1 year and 4 years (P=0.49). Among the preoperative factors, number of previous intraocular surgeries (hazard ratio of 2.24; 95% CI, 1.14-4.37, was significantly associated with failure; P=0.01). Tube-related complications (16%) were similar in both the groups. One eye in each group had sight-threatening complication. AGV implantation had good success rate in refractory pediatric glaucoma. The success rates were similar in PCG and SPG as were the complications. Number of prior intraocular surgeries was a risk factor for failure.

Intraoperative testing of opening and closing pressure predicts risk of low intraocular pressure after Ahmed glaucoma valve implantation.

The aim of this study was to assess whether intraoperative testing of silicone Ahmed glaucoma valves (AGVs) would identify valves with an increased risk of low postoperative intraocular pressure (IOP). In 30 consecutive cases of glaucoma surgery with AGV implantation, after priming the AGV, we intraoperatively measured the opening pressure A, closing pressure B, and re-opening pressure C using the active infusion pump of a phako-machine. IOP was checked postoperatively on the same day. Low IOP was defined as <5 mm Hg. Intraoperatively measured pressure characteristics of the valve function were analysed for their ability to predict postoperative IOP outcomes. Opening A, closing B, and re-opening C pressures (mean, (SD)) were 18.4 (5.1), 8.3 (4.7), and 11.7 (4.8)mm Hg, respectively. Ten patients (33.3%) had low IOP. An opening pressure of ≤18 mm Hg predicted low postoperative IOP with a sensitivity (10/10) of 100% (95% CI, 69.2-100) and a specificity (13/20) of 65.0% (95% CI, 40.8-84.6). AGVs have a high variability of opening, closing, and re-opening pressures. An opening pressure of ≤18 mm Hg, a closing pressure of ≤10 mm Hg, or a re-opening pressure of ≤11 mm Hg identified all patients with low postoperative IOP.

Ahmed glaucoma valve in eyes with preexisting episcleral encircling element.

Background:To describe the use of Ahmed glaucoma valve (AGV) in the management of intractable glaucoma in eyes with a preexisting episcleral encircling element.Materials and Methods:This is a retrospective, consecutive, noncomparative study. The study included 12 eyes of 12 patients with a preexisting episcleral encircling element that underwent implantation of silicone AGV to treat intractable glaucoma during January 2009 to September 2010.Results:The mean patient age was 25.6 (standard deviation 17.1) years. Five (41.6%) patients were monocular. The indications for AGV were varied. The mean duration between placement of episcleral encircling element and implantation of AGV was 30.5 (33.8) months. The mean follow-up was 37.4 (22.9) weeks. Preoperatively, the mean intraocular pressure (IOP) was 31.4 (7.9) mmHg and the mean antiglaucoma medications were 2.8. At the final postoperative follow-up, the mean IOP was 12.5 (3.5) mmHg and the mean number of antiglaucoma medications was 0.8 (P < 0.001). The complications observed over the follow-up period did include corneal graft failure in three eyes, tube erosion in two eyes and rhegmatogenous retinal detachment in one eye.Conclusion:AGV is an effective option in the management of intractable glaucoma in eyes with a preexisting episcleral encircling element keeping in mind the possibility of significant postoperative complications.

Polypropylene vs silicone Ahmed valve with adjunctive mitomycin C in paediatric age group: a prospective controlled study

To compare the results of silicone and polypropylene Ahmed glaucoma valves (AGV) implanted during the first 10 years of life. A prospective study was performed on 50 eyes of 33 patients with paediatric glaucoma. Eyes were matched to either polypropylene or silicone AGV. In eyes with bilateral glaucoma, one eye was implanted with polypropylene and the other eye was implanted with silicone AGV. Fifty eyes of 33 children were reviewed. Twenty five eyes received a polypropylene valve, and 25 eyes received a silicone valve. Eyes implanted with silicone valves achieved a significantly lower intraocular pressure (IOP) compared with the polypropylene group at 6 months, 1 year, and 2 years postoperatively. The average survival time was significantly longer (P=0.001 by the log-rank test) for the silicone group than for the polypropylene group and the cumulative probability of survival by the log-rank test at the end of the second year was 80% (SE: 8.0, 95% confidence interval (CI): 64-96%) in the silicone group and 56% (SE: 9.8, 95% CI: 40-90%) in the polypropylene group. The difference in the number of postoperative interventions and complications between both groups was statistically insignificant. Silicone AGVs can achieve better IOP control, and longer survival with less antiglaucoma drops compared with polypropylene valves in children younger than 10 years.

Comparison of the Outcome of Silicone Ahmed Glaucoma Valve Implantation with a Surface Area between 96 and 184 mm2in Adult Eyes

PurposeTo compare the success rates, complications, and visual outcomes between silicone Ahmed glaucoma valve (AGV) implantation with 96 mm2 (FP8) or 184 mm2 (FP7) surface areas.MethodsThis study is a retrospective review of the records from 132 adult patients (134 eyes) that underwent silicone AGV implant surgery. Among them, the outcomes of 24 eyes from 24 patients with refractory glaucoma who underwent FP8 AGV implantation were compared with 76 eyes from 76 patients who underwent FP7 AGV implantation. Preoperative and postoperative data, including intraocular pressure (IOP), visual acuity, number of medications, and complications were compared between the 2 groups.ResultsThere were no significant differences in baseline characteristics between the 2 groups (p > 0.05). The postoperative visual acuity of the patients in the FP8 group was better than that of the patients in the FP7 group in some early postoperative periods (p < 0.05); however, after 10 postoperative months, visual acuity was not significantly different through the 3-year follow-up period (p > 0.05). Postoperative IOP was not significantly different between the 2 groups (p > 0.05) except for IOP on postoperative day 1 (11.42 mmHg for the FP7 group and 7.42 mmHg for the FP8 group; p = 0.031). There was no statistical difference in success rates, final IOP, number of medications, or complication rates between the 2 groups (p > 0.05).ConclusionsThe FP7 and FP8 AGV implants showed no difference in terms of vision preservation, IOP reduction, and number of glaucoma medications required.

Silicone Ahmed Glaucoma Valve With and Without Intravitreal Triamcinolone Acetonide for Neovascular Glaucoma

To compare the effect on intraocular pressure (IOP) of the silicone Ahmed glaucoma valve with and without an intravitreal injection of triamcinolone acetonide. Forty-nine patients with clinically uncontrolled neovascular glaucoma were included in the study; 22 were randomly assigned to the study group (silicone Ahmed glaucoma valve implant with intravitreal triamcinolone acetonide) and 27 to the control group (silicone Ahmed glaucoma valve). IOP was the primary outcome measure in this study. The secondary outcome measure was success, defined by IOP lower than 22 mm Hg and higher than 5 mm Hg, and no serious complications. Success rates in both the groups were compared using Kaplan-Meier survival curves and the log-rank test. IOP levels were compared using mixed linear model analysis to correct for repeated measures correlation. Forty-three patients, 18 in the study group and 25 in the control group, completed the study (follow-up of 12 mo). The mean IOP was significantly lower after 1 year in both the groups (P<0.001). The mean IOP in the first month of follow-up was lower in the study group (control; 20.4±9.7, study; 13.6±6.5, P<0.01). The success rate at 1 year was 78% for the study group and 76% for the control group (P=0.82). Complication rates were not different between the groups. Intravitreal injection of triamcinolone acetonide in neovascular glaucoma did not affect the intermediate-term success of the silicone Ahmed valve nor reduce the incidence of complications. The mean IOP spike in the first month was lower in the triamcinolone group.

Comparison of polypropylene and silicone Ahmed valve survival 2 years following implantation in the first 2 years of life

Aim:To compare the 2-year survival rates of polypropylene and silicone Ahmed glaucoma valves (AGVs) implanted during the first 2 years of life.Methods:Retrospective analysis of polypropylene and silicone AGV implantation during...

Assessment of Closing Pressure in Silicone Ahmed FP7 Glaucoma Valves

To measure closing pressure in a series of new Model FP7 silicone Ahmed Glaucoma Valves (AGVs), using an in vitro gravity-driven system, in which closing pressure was measured directly from a dual manometer/pressure reservoir. A straight length of tubing served as an open manometer, which connected via a 3-way stopcock to the inlet of the AGV submerged under 1.5 cm of balanced saline solution (BSS). Six AGV were assessed in 5 sequential trials and the mean inlet pressure at 90 minutes was recorded as the closing pressure. After testing, a single valve was primed a second time using greater force and retested. Control trials were performed with a submerged 26-G cannula opening directly into the BSS bath. At 90 minutes, the 6 valves equilibrated at a mean inlet pressure of 7.1 mm Hg, with a range from 1.4 to 13.5 mm Hg. Closing pressures at or less than 5 mm Hg were measured in half (3/6) of the valves tested. The average flow of BSS across the valves in the final 30 minutes was less than 1.5x10(-2) microL/min. In the single valve reperfused under greater pressure, the closing pressure increased. Model FP7 AGVs, in vitro, exhibit significant variability in closing pressure, with half closing at intraocular pressures considered potentially problematic in clinical situations. The results of the high-pressure perfusion experiment suggest that more research into the priming process is required so a precise description can be developed for surgeons.

Comparison of Safety and Efficacy Between Silicone and Polypropylene Ahmed Glaucoma Valves

Purpose: To compare the safety and efficacy of polypropylene and silicone Ahmed glaucoma valves (AGVs). Methods: The medical records of 62 consecutive refractory glaucoma patients who had undergone AGV implantion from March 2003 to December 2005 were reviewed retrospectively. Among the 62 patients, 32 patients underwent polypropylene AGV implantation (group P) and the other 30 patients underwent silicone AGV implantation (group S). Postoperative IOP, the complication rate, and the success rate were compared between the two groups. Results: The life-table success rates for the group P were 81.3% at 6 months and 71.2% at 12 months, and the success rates for the group S were 89.9% at 6 months and 78.6% at 12 months, showing no significant difference between the two groups. Complications, including non-tube-related complications, were observed more frequently in the group S, but there was no significant difference between the two groups. Conclusions: The silicone AGV can reduce IOP effectively but may be associated with non-tube-related complications. J Korean Ophthalmol Soc 49(5):791-797, 2008

Comparison of Polypropylene and Silicone Ahmed Glaucoma Valves

To evaluate and compare the clinical outcomes after implantation of the silicone plate and the polypropylene plate Ahmed Glaucoma Valves. Prospective, multicenter, comparative series. A total of 132 patients with uncontrolled glaucoma were treated with either the silicone or polypropylene Ahmed Glaucoma Valve implant. Success was defined according to 2 criteria: (1) intraocular pressure (IOP) of 6 mmHg or more or 21 mmHg or less, and (2) IOP reduction of at least 30% relative to preoperative values. Eyes requiring further glaucoma surgery, including cyclophotocoagulation, or showing loss of light perception were classified as failures. Average follow-up was 12.8 months (range, 6-30 months) for the silicone plate group and 14.5 months (range, 6-30 months) for the polypropylene plate group (P = 0.063). At the last follow-up examination, the mean IOP was 13.8+/-3.9 mmHg and 17.3+/-6.5 mmHg (P<0.0001) and the mean number of antiglaucoma medications was 1.9+/-1.3 and 2.1+/-1.4 (P = 0.48) in the silicone plate and polypropylene plate groups, respectively. The life-table success rates for the silicone plate and polypropylene plate groups were 94.2% and 83.2% at 12 months and 82.4% and 56.7% at 24 months by definition 1, respectively (P = 0.035). When an IOP reduction of at least 30% was used for success criterion (definition 2), probabilities of success were 89.5% and 71.7% at 12 months and 78.3% and 68.5% at 24 months in the silicone and the polypropylene plate groups, respectively (P = 0.012). Visual outcomes were comparable between the 2 groups. However, complications including Tenon's cyst were observed more frequently in the polypropylene plate than in the silicone plate group (P<0.05). The silicone Ahmed Glaucoma Valve (model FP7) showed improved IOP reduction compared with the polypropylene (model S2) implant. Differences observed in mean IOP, success rate, and complications suggest that plate material may influence clinical outcome.

Comparison of Safety and Efficacy between Silicone and Polypropylene Ahmed Glaucoma Valves in Refractory Glaucoma

To compare the safety and efficacy of polypropylene and silicone Ahmed glaucoma valves (AGVs) over 1 year of follow-up. Retrospective comparative study. Fifty consecutive patients with polypropylene and 49 consecutive patients with silicone AGV implantation. Our hospital instituted a formulary conversion of the glaucoma aqueous drainage device from polypropylene to silicone AGVs in January 2003. We reviewed the polypropylene AGVs within 7 months before and the silicone AGVs within 7 months after the date of conversion performed on patients with glaucoma refractory to medical treatment and filtering procedures, without previous drainage devices or cyclodestructive procedures, and with a minimum of 12 months' follow-up. Surgical success was defined as an intraocular pressure (IOP) reduction of > or =20% and a final IOP of >5 and <22 mmHg, without additional surgical intervention for IOP control, loss of light perception, or serious complications. The 2 groups were compared for IOP control, visual outcome, complication rate, and surgical success rate. Significant IOP reductions occurred after polypropylene AGV implantation (from 32.4+/-11.3 mmHg to 16.5+/-6.9 mmHg, P<0.0001) and silicone AGV implantation (from 32.6+/-12.6 mmHg to 14.7+/-6.9 mmHg, P<0.0001). The silicone group had a lower mean IOP than the polypropylene group at all postoperative visits, but the differences were significant only at 3 months postoperatively (P = 0.014). In addition, the silicone group was associated with a rate of insufficient IOP control as the reason of failure (IOP of > or =22 mmHg or IOP reduction of <20%) lower (4.1%) than that of the polypropylene group (20.0%, P = 0.015), but a rate of non-tube related serious complications (16.3%) higher than that of the polypropylene AGV (4.0%, P = 0.042). After 1 year of follow-up, the silicone AGV is at least as effective as the polypropylene AGV in IOP reduction but may be associated with a higher rate of complications. These differences are important for surgeons converting to use of the silicone AGV in patients with glaucoma refractory to other forms of treatment.