Nonvalved Glaucoma Drainage Research Articles

Evaluating the Safety and Efficacy of a Novel Glaucoma Drainage Device in High-Risk Adult Glaucoma Patients: A One-Year Pilot Study.

Background: We report on the 12-month safety and efficacy outcomes of a new non-valved glaucoma drainage device, the eyePlate-300 (Rheon Medical, Lausanne, Switzerland), in managing refractory glaucoma. Methods: A retrospective review was conducted on consecutive patients over 18 who underwent glaucoma drainage device (GDD) surgery with the eyePlate-300 after a single glaucoma consultation between February 2020 and April 2021, with at least 12 months of documented post-op follow-up. Results: A total of 16 eyes from 15 patients were included. Complete success was observed in 47% of patients and overall success in 83%. The mean IOP decreased from 31.5 mm Hg to 10.7 mm Hg (67% reduction from baseline), and the number of IOP-lowering drops was reduced from 3.1 to 0.7 at one year. The mean BCVA remained stable. No additional IOP-lowering surgeries were required, and no severe sight-threatening complications were noted. Conclusions: The initial one-year results suggest that the eyePlate could be a safe and effective device for reducing IOP in an ethnically diverse refractory glaucoma population. Further follow-up is necessary to determine the long-term safety and efficacy.

Ahmed ClearPath vs. Baerveldt Glaucoma Implant: A Retrospective Noninferiority Comparative Study

To compare the efficacy and safety of two non-valved glaucoma drainage devices (GDDs): Ahmed ClearPath (ACP) vs. Baerveldt glaucoma implant (BGI). Single-center, retrospective, comparative study. Consecutive patients who underwent ACP or BGI surgery for glaucoma (250 mm2 or 350 mm2 models), and had ≥6 months of follow-up and no prior GDD implantation. Chart review of ACP or BGI surgery in patients with glaucoma at Wills Eye Hospital (2020-2023). The primary outcome measure was surgical failure at the end of follow-up, defined as intraocular pressure (IOP) >21 or <6 mmHg at 2 consecutive visits, progression to no light perception (NLP) vision, glaucoma reoperation, or implant removal. Secondary outcome measures included the rate of postoperative complications and changes in best corrected visual acuity (BCVA), IOP, and glaucoma medications. A total of 128 eyes of 113 patients (63 ACP, 65 BGI) with similar baseline characteristics and a mean follow-up duration of 19.6±10.8 (median 20.5) months were included. Surgical failure occurred in 12 eyes (9.4%) with no significant difference between ACP and BGI eyes (9.5% vs. 9.2%, respectively; P=0.810). Reasons for failure included IOP >21 mmHg (3/12, 25.0%), glaucoma reoperation (5/12, 41.7%), and tube removal (4/12, 33.3%). No eyes progressed to NLP vision. Kaplan-Meier survival analysis showed similar cumulative rate of surgical failure in both groups (P=0.871). Both groups achieved significant IOP and medication reduction compared to their baseline. Final IOP, BCVA, and complication rate was similar in both groups, but medication number was significantly lower in the ACP group (P=0.012). Both the 250 mm2 and 350 mm2 models had similar outcomes, but diplopia was significantly associated with the 350 mm2 model of either implant (P=0.012). Univariate logistic regression analysis did not identify either tube type or plate size as predictors of surgical failure. To our knowledge, this is the first study to compare the recently approved ACP vs. the BGI. Both implants had similar surgical failure and complication rate. Final IOP was similar in both groups, but ACP achieved lower medication number. Diplopia was significantly associated with the use of 350 mm2 model of either implant. Neither tube type nor plate size were significant predictors of surgical failure.

The effects of the first versus second glaucoma drainage implant surgery in patients with primary open-angle glaucoma

BackgroundTo investigate the outcome of non-valved glaucoma drainage implant surgery (GDIS) in primary open-angle glaucoma (POAG) patients divided in the first GDI group (patients who underwent the first GDIS) and the second GDI group (patients who underwent the second GDIS because of the failed first GDIS).MethodsIntraocular pressure (IOP), visual acuity (VA), visual field defect (VFD), medication score (MS), survival rate of GDIS, complications, and patient background was retrospectively analyzed. Two success criteria were set: Criteria (1) IOP reduction ≥ 20% and 5 < IOP ≤ 21, Criteria (2) IOP reduction ≥ 20% and 5 < IOP ≤ 14.ResultsThere were 136 eyes of 109 patients in the first GDI group and 32 eyes of 27 patients in the second GDI group. In the first GDI group and II, mean preoperative IOP was 26.7 ± 6.7 mmHg and 23.7 ± 3.5 mmHg, respectively (P = 0.09). No statistically significant difference in postoperative IOP reduction was found between the two groups (P = 0.39). At 5-years postoperative, the Criteria 1 (Criteria 2) survival rate in the first GDI group and the second GDI group was 60.4% (31.7%) and 61.2% (25.6%), respectively (Criteria 1: hazard ratio [HR]: 0.64, 95% confidence interval [CI]: 0.30–1.35 [P = 0.24]; Criteria 2: HR: 0.81, 95% CI: 0.46–1.44, P = 0.48). No significant difference in VA, VFD change, MS, or complications was observed. Young patient age was the only significant factor for failure in the first GDI group (odds ratio: 0.95, 95% confidence interval: 0.91-1.00, P = 0.03).ConclusionThe second GDIS may be as effective as the first GDIS for IOP reduction in POAG patients, however, there is a high risk of failure in young-age patients and the surgery may be ineffective in eyes requiring Criteria 2.

The outcomes of a low-cost, non-valved glaucoma drainage device using mitomycin-C: 1-year results.

To evaluate the indications, outcomes, and complications of the usage of Aurolab Aqueous Drainage Implant (AADI) using mitomycin-C. A retrospective case series of patients who underwent AADI placement using mitomycin-C between April 2018 and June 2020 at Ain Shams University Hospitals, Cairo, Egypt. The data was extracted from the records of the patients with a minimum of 1year of follow-up. Complete success was defined as IOP ≥ 5mmHg and ≤ 21mmHg or reduction of IOP by ≥ 20% from baseline without antiglaucoma medications (AGMs). Qualified success was defined as reaching the same IOP range with the aid of AGM. A total of 50 eyes of 48 patients were included. Neovascular glaucoma represented the commonest indication (13 patients, 26%). The mean preoperative IOP was 34.0 ± 7.1mmHg, with a median number of AGM of 3 (mean ± SD = 2.84 ± 1), while the mean IOP after 12months was 14.3 ± 4 with a median number of AGM of 0. (mean ± SD = 0.52 ± 0.89) (p < 0.001). Complete success was achieved in 33 patients (66%). Qualified success was achieved in 14 patients (28%). Thirteen eyes (26%) had variable postoperative complications; none of them required explantation of the device or affected the visual acuity (except one patient). AADI with using mitomycin-C and ripcord during the surgery is an effective and relatively safe method of control of IOP in refractory and advanced cases of glaucoma, with an overall success rate of 94%.

Internal Tube Occlusion with An Easily Removable Non-Absorbable Double Suture: A Novel Surgical Technique Adjunct for Non-Valved Glaucoma Drainage Devices

To describe a surgical variant for non-valved glaucoma drainage device implants using an easily removable non-absorbable double suture into the lumen of the tube. A retrospective, non-comparative case series of 10 patients who underwent a non-valved glaucoma drainage device implant with an endoluminal double-suture for refractory glaucoma. The sutures were easily removed postoperatively without the need for an operating room. Intraocular pressure, number of medications, and early and late complications were evaluated with a follow-up of 12 months. None of the eyes that underwent an operation developed early or late complications. The first endoluminal suture was removed in all eyes with a mean time of removal of 30 ± 7 days. The second suture was removed in all eyes with a mean time of removal of 90 ± 7 days. No complications were noted, either, after or during suture removal. The mean preoperative IOP was 27.3 ± 4.0 and the postoperative IOP, at the end of the follow-up, was 12.7 ± 1.4. At the end of the follow-up, six patients (60%) achieved complete success and four patients (40%) achieved qualified success. In conclusion, in our case series, the surgical variant allowed for a safe and gradual regulation of the flow during postoperative management. Considering the efficacy of non-valved glaucoma drainage devices, an improvement in the safety profile allows surgeons to broaden the surgical indications.

Safety and efficacy of Aurolab aqueous drainage implant in refractory glaucoma: A prospective study.

This study was conducted to assess the intraocular pressure (IOP) control and postoperative complications following a non-valved glaucoma drainage device (GDD) surgery in refractory glaucoma. This was a prospective interventional study conducted on patients with glaucoma refractory to maximal medications or failed surgical treatment who underwent Aurolab aqueous drainage implant (AADI; Aurolabs, India) surgery. Primary outcome measures were IOP control, postoperative complications, and reduction in the number of antiglaucoma medications (AGM). Thirty-four eyes were analyzed and the mean follow-up was 16.06 ± 5.63 months. The preoperative median (Q1, Q3) IOP was 31 mmHg (28, 36.5) which decreased to 12 mmHg (12, 14) at 6 months postoperatively. The median (Q1, Q3) number of AGMs decreased from 3 (3, 4) to 0 (0, 1). Significant complications like implant extrusion and tube exposure were noted in two eyes. The total success and failure rates at 6 months were 91.1% and 8.8%, respectively. AADI is effective in achieving target IOP and significantly reduces the use of AGMs with good safety in the short term. Long-term follow-up studies are needed to assess long-term IOP control and cost-effectiveness.

Placement and Extension of Glaucoma Drainage Devices Using Polypropylene Suture in Pediatric Patients.

Glaucoma drainage device tube placement and extension in pediatric patients may be complicated by abnormal anterior segment anatomy and corneal opacities. The authors describe two techniques for placement and extension of non-valved glaucoma drainage device tubes using polypropylene suture as a guidewire and stabilizer, respectively. [J Pediatr Ophthalmol Strabismus. 2022;59(5):e62-e65.].

Short-term surgical outcomes of twin-site combined phaco-emulsification and mitomycin-C augmented trabeculectomy in pseudo-exfoliation glaucoma versus primary open-angle glaucoma.

To compare the short-term outcomes of combined phaco-emulsification with posterior chamber intra-ocular lens and mitomycin augmented trabeculectomy in patients with pseudo-exfoliation glaucoma (PXFG) versus primary open-angle glaucoma (POAG). A total of 144 eyes of 144 patients were enrolled in this prospective interventional comparative study, 72 each of which had PXFG and POAG, respectively. All patients underwent twin-site combined phaco-trabeculectomy at a tertiary eye center in India between December 2017 and December 2018 and were followed up for a period of 12 months. The main outcome measures were intra-ocular pressure (IOP), best corrected visual acuity (BCVA), total surgical time, rate of intra-operative and post-operative complications, and the number of ocular hypotensive medications needed. Success rates were determined via Kaplan-Meier survival analysis. The mean age was 63.9 ± 7.9 years in the POAG group and 66.4 ± 6.8 years in the PXFG group (P - 0.04). The baseline BCVA, IOP, and cup-disc ratio were comparable between two groups. Intra-operative complications and post-operative outcomes were comparable between the two groups. There was a significant drop in anti-glaucoma medications in both groups. Six patients, three (4.2%) in each group, were lost to follow-up after 6 months. Three patients (4.2%) in PXFG needed additional glaucoma intervention for controlling IOP, one patient needed a non-valved glaucoma drainage device, and two patients required diode cyclo-photocoagulation within the follow-up period. Patients with PXFG had a longer surgical time than POAG. Similar success and complication rates were observed following combined twin-site phaco-trabeculectomy in both POAG and PXFG at 1 year. Combined glaucoma surgery resulted in good IOP control, improvement in BCVA, and lower requirement of ocular hypotensives in both the groups.

A Novel Tube Insertion Technique for Glaucoma Drainage Device Implantation.

Early hypotony after non-valved glaucoma drainage device (GDD) implantation for complex glaucomatous eyes with labile aqueous production can lead to significant visual morbidity. We therefore sought to report the early postoperative outcomes of a novel surgical technique that allows atraumatic insertion of non-valved GDDs through a much smaller 25-gauge scleral track, to minimize entry site leakage and improve safety. Retrospective case series of 15 consecutive cases undergoing non-valved GDD insertion into the anterior chamber using a previously unreported technique. All eyes underwent successful GDD insertion using our novel technique, with no intraoperative complications. The mean preoperative intraocular pressures (IOP), at day 1, week 1 and week 3 were 31.4, 22.4, 23.7, and 25.6 mm Hg, respectively. A statistically significant IOP reduction was achieved at day 1, week 1 and week 3 postoperatively ( P <0.05) without any observed leakage at the scleral entry site. One eye (6.7%) with complex panuveitic glaucoma developed early hypotony (5mm Hg) with shallow choroidal detachments on day 1. This was successfully managed with 1 intracameral ophthalmic viscoelastic device injection given at the slit-lamp and no further intervention. This novel single needle-docking intraocular insertion manoeuvre is an easily adoptable technique to make GDD insertion through a smaller 25-gauge water-tight scleral track more efficient and less traumatic. The technique reduces scleral distortion and therefore improves surgical safety particularly in eyes with complex secondary glaucoma.

Commentary: Meeting the nemesis of a non-valved glaucoma drainage device head-on.

Commentary: Meeting the nemesis of a non-valved glaucoma drainage device head-on.

Primary tubes in siblings of a South Indian family with total aniridia and glaucoma

Aniridia is an uncommon hereditary bilateral panocular disorder affecting not only the iris but also the cornea, anterior chamber angle, lens, retina, and optic nerve with associated life-threatening conditions. Glaucoma is associated with aniridia in around 50% of the cases and usually develops in the first two decades of life. The treatment of glaucoma is challenging and often needs surgical intervention to achieve adequate intraocular pressure (IOP) control in cases refractory to medical treatment. Here, we report the familial nature of aniridia with secondary glaucoma and discuss the challenges in the management with a comprehensive review of the literature. The elder one, a 16-year-old girl presented with absolute glaucoma in the right eye and high IOP with advanced disk damage in the left eye for which she underwent a non-valved glaucoma drainage implantation. The younger one, a 12-year-old boy presented with a high IOP of more than 40 mmHg in both eyes (OU) for which he underwent sequential glaucoma drainage devices (GDD) implantation in OU. The intermediate-term outcomes in both of them showed a well-placed Aurolab aqueous drainage implant (AADI) tube with adequately controlled IOP.

Sign of filtration in non-valved glaucoma drainage device

Sign of filtration in non-valved glaucoma drainage device

Comparison of Outcomes of Glaucoma Drainage Implant Surgery With or Without Prior Failed Trabeculectomy.

A comparison of 186 glaucoma patients with mixed diagnoses who underwent nonvalved glaucoma drainage device (GDD) implant surgery showed similar long-term intraocular pressure (IOP), medication, and visual acuity (VA) outcomes between those with prior failed trabeculectomy surgery versus those without. The purpose of this study was to evaluate whether prior failed trabeculectomy adversely affects the outcome of glaucoma tube surgery. A total of 186 eyes of 186 patients who underwent a nonvalved GDD implant surgery by a single surgeon between 1996 and 2015 at a University practice were included. Patients were of mixed diagnoses and over 18 years old. Before the GDD surgery, 65 had a previous failed glaucoma filtering surgery and 121 had no prior glaucoma surgery. Demographic information, preoperative and postoperative IOP, medication, VA, and complications were collected from chart review. No significant difference was noted in mean IOP and mean medication use (13.0 and 12.6 mm Hg on 2.0 and 1.7 medication classes at 5 y postoperatively, respectively), mean VA and change in VA from baseline, or numbers of complications (P>0.05), between eyes that had a prior failed filtration surgery and those that had not. Kaplan-Meier plots for failure over 5 years using a lower limit of <5 mm Hg and an upper limit of ≥18, ≥15, or ≥12 mm Hg did not show a significant difference between groups. Subanalyses were performed to examine only primary glaucoma eyes and results were similar. Further group subanalyses comparing those with baseline IOP ≥25 or <25 mm Hg, age 65 and above or below 65 years and those specifically with Baerveldt 350 mm2 implants also did not show significant differences. Prior failed filtration surgery does not appear to affect the outcome of future GDD surgery.

One stage non-valved glaucoma drainage device in refractory glaucoma under cover of oral propranolol for presumed choroidal hemangioma in Sturge-Weber syndrome

One stage non-valved glaucoma drainage device in refractory glaucoma under cover of oral propranolol for presumed choroidal hemangioma in Sturge-Weber syndrome

Early-Onset Glaucoma Manifesting as Buphthalmos in an Infant with Phakomatosis Pigmentovascularis Type IIa

Abstract Phacomatosis pigmentovascularis (PPV) is a rare type of phakomatosis characterized by co-existence of vascular nevus and pigmentary nevus with or without extracutaneous systemic involvement.Presentation of this rare entity is uncommon among infantile age group and bilateral glaucoma with megalocornea in PPV is exceedingly rare.We present a rare case of bilateral buphthalmos associated with PPV type IIa in a seven-month child who had nonvalved glaucoma drainage device(GDD) in right eye(OD) &combined trabeculotomy+ trabeculectomy in left eye(OS), followed by successful control of intraocular pressure(IOP) for the period of 18 months follow up.We discuss challenges in management with a comprehensive review of literature.

Two-Year Outcomes of the New Low-cost Nonvalved Aurolab Aqueous Drainage Implant in Refractory Glaucoma.

This study aimed to report the 2-year surgical outcomes in terms of efficacy and safety of the relatively new, indigenously manufactured, low-cost nonvalved drainage device Aurolab Aqueous Drainage Implant (AADI) in the management of refractory glaucomas in the Indian population. A retrospective review of consecutive patients older than 12 years, who underwent nonvalved glaucoma drainage device surgery via AADI, was performed by a single fellowship-trained surgeon, between January 2014 and January 2018, who had at least 12 months of documented postoperative follow-up. Primary-intraocular pressure (IOP).Secondary-number of antiglaucoma medication (AGM), LogMAR best-corrected visual acuity and complications.Complete success was defined as IOP ≥5 and ≤21 mm Hg; qualified success was defined as fulfilling the above criteria with the use of AGM. Failure was defined as the inability to fulfill the IOP criteria, loss of perception of light, explantation, or any additional glaucoma surgery. A total of 48 eyes of 46 patients were included with a median follow-up of 24 months (quartile 1=16, quartile 3=31.25; interquartile range=15.25) (mean=24.9 mo; SD=10.1). The IOP and number of AGM required was significantly lower at every timepoint postoperatively (P<0.001). The median LogMAR best-corrected visual acuity remained unchanged (P=0.307). Complications occurred in 21 patients (43.7%); some eyes had >1 complication. Complete success was seen in 56.3%; overall success was 87.5%. The safety and efficacy of the new nonvalved glaucoma drainage device, AADI, remain in its second year after implantation. Still further follow-up is recommended, as it has the ability to breach the cost barrier in newly industrialized nations worldwide.

Baerveldt implant versus trabeculectomy as the first filtering surgery for uncontrolled primary congenital glaucoma: a randomized clinical trial.

Our initial goal was to compare the efficacy and safety of a glaucoma drainage device and trabeculectomy for children with primary congenital glaucoma after angular surgery failure. However, we discontinued the study due to the rate of complications and wrote this report to describe the results obtained with the two techniques in this particular group. This was a parallel, non-masked, controlled trial that included patients aged 0-13 years who had undergone previous trabeculotomy or goniotomy and presented inadequately controlled glaucoma with an intraocular pressure ≥21 mmHg on maximum tolerated medical therapy. We randomized the patients to undergo either placement of a 250-mm2 Baerveldt glaucoma implant or mitomycin-augmented trabeculectomy. The main outcome measure was intraocular pressure control. We calculated complete success (without hypotensive ocular medication) and qualified success (with medication) rates. We defined failure as uncontrolled intraocular pressure, presence of serious complications, abnormal increase in ocular dimensions, or confirmed visual acuity decrease. We studied 13 eyes of 13 children (five in the glaucoma drainage device group; eight in the trabeculectomy group). Both surgical procedures produced a significant intraocular pressure reduction 12 months after intervention from the baseline (tube group, 22.8 ± 5.9 mmHg to 12.20 ± 4.14 mmHg, p=0.0113; trabeculectomy group, 23.7 ± 7.3 mmHg to 15.6 ± 5.9 mmHg, p=0.0297). None of the patients in the tube group and 37.5% of those in the trabeculectomy group achieved complete success in intraocular pressure control after 12 months of follow-up (p=0.928, Chi-square test). Two patients (40%) had serious complications at the time of tube aperture (implant extrusion, retinal detachment). Both the tube and trabeculectomy groups presented similar intraocular pressure controls, but complete success was more frequent in the trabeculectomy group. Non-valved glaucoma drainage devices caused potentially blinding complications during tube opening. Because of the small sample size, we could not draw conclusions as to the safety data of the studied technique.

Comparative Outcomes of the Molteno3 and Baerveldt Glaucoma Implants

To compare outcomes between 2 nonvalved glaucoma drainage devices (GDDs) used to treat refractory glaucoma or in patients with neovascular/uveitic glaucoma likely to be poorly responsive to less aggressive therapies. Retrospective, nonrandomized, multicenter comparative study. A total of 117 eyes from 117 patients. Retrospective chart review of patients who underwent implantation of the Baerveldt (BGI) (Abbott Medical Optics, Abbott Park, IL) or the Molteno3 glaucoma implant (MGI) (Molteno Ophthalmic Limited, Dunedin, New Zealand). Noninferiority of the MGI versus the BGI was tested with Cox and mixed-effects regression models. Interventions in each group were analyzed with chi-square tests. The primary outcome was time until device failure, defined as intraocular pressure (IOP) >21 mmHg or a reduction <20%, hypotony, reoperation for glaucoma, or loss of light perception. Secondary outcomes were intraoperative time, postoperative IOP, number of IOP-lowering medications, and visual acuity (VA). The MGI could not be deemed noninferior to the BGI with regard to time until device failure (hazard ratio [HR], 0.83; confidence interval [CI], 0.41-1.65). The MGI was noninferior to the BGI when comparing postoperative IOP, a difference of-0.40 mmHg (95% CI,-1.74-0.93). The MGI needed 2% fewer medications (ratio of 0.98, 95% CI, 0.79-1.22), but noninferiority could not be claimed. With regard to VA, the MGI's mean was 0.10 logarithm of the minimum angle of resolution (logMAR) higher (95% CI,-0.01-0.21), but noninferiority testing was again inconclusive. Intraoperative time for the MGI was 15.7 minutes shorter versus the 350 mm2 plate size BGI (P < 0.001) and 4.3 minutes shorter versus the 250 mm2 plate size BGI (P= 0.32). More patients in the MGI group needed secondary operative management (11%, P= 0.03). The MGI was noninferior to the BGI in lowering IOP. Differences in time until device failure, VA outcomes, and medication use were inconclusive. The MGI required more secondary operative interventions. The MGI required less time to implant than the BGI's 350 mm2 plate size implant. Overall, the use of both GDDs is justifiable to lower IOP when more conservative management has failed.

Ab interno tube ligation for refractory hypotony following non-valved glaucoma drainage device implantation

PurposeTo report the 2-year outcomes of a novel surgical technique allowing reduction of the intraluminal diameter of the tube without total tube occlusion in order to allow enough increase in outflow resistance to permit resolution of hypotony whilst also achieving adequate IOP control.MethodsThis was a single-surgeon retrospective case note review of all non-valved GDD cases over an 8-year period (2008–2015) that underwent ab interno ligation of the drainage tube in order to manage post-operative hypotony (Baerveldt or Molteno). Twelve eyes of 12 patients (4.4%) developing refractory hypotony that did not respond to multiple intracameral ophthalmic viscoelastic device (OVD) injections were included in this retrospective case series and were treated with our ab interno tube ligation technique. The post-ligation management algorithm consisted of re-instating topical anti-glaucoma agents, laser suture lysis (LSL), or further ab interno ligation.ResultsMean IOP increased from 2.8 mmHg at baseline to 7.8 mmHg, 7.1 mmHg, 9.0 mmHg, 13.6 mmHg, 10.9 mmHg, 13.9 mmHg and 13.6 mmHg at day 1, week 1, month 1, month 3, month 6, year 1 and year 2 respectively, with or without additional topical anti-glaucoma medications. Although hypotony resolution following our technique was achieved in all eyes at 2 years, 8.3% of cases required reinstatement of topical medications to maintain IOP control within the target range.ConclusionsWe propose ab interno partial tube tying as an effective surgical option to achieve an immediate, predictable and sustained IOP elevation either as a primary procedure or when traditional methods have failed to resolve hypotony in eyes with non-valved GDDs.

Effects of the Numbers and the Shapes of Venting Slits on Intraocular Pressure after Baerveldt Glaucoma Drainage Implant

ABSTRACTPurpose: Venting slits are widely used as an effective method to avoid the high intraocular pressure (IOP) phase immediately after the implantation of non-valved glaucoma drainage devices. However, there have been no detailed reports comparing the types of needles used and the numbers of slits made. In this study we investigated the effects of different needle types and the number of venting slits.Methods: IOP was measured using a Keyence NR-600 transducer connected to the limbus of a pig eye with a 27G needle. A microsyringe pump was also connected to the corneal limbus using a 27 G needle to make a continuous perfusion system at the rate of 200 μl/hr. The silicone tube of a Baerveldt glaucoma drainage implant (BG101-350) was ligated near the plate and then implanted in the anterior chamber of the pig eye. The tube was covered with scleral tissue of another pig eye after 1 or 3 venting slits were created in the middle of the outer diameter using different types of needles (7–0 Vicryl®, 7–0 PDSⅡ®, 5–0 PDSⅡ®, 3–0 PDS Plus®). IOP measurement was started from 50 mmHg and then we monitored the chronological changes of IOP for 15 minutes.Results: The IOPs at 15 minutes after continuous perfusion with the venting slits made using 7–0 Vicryl needles were 29.0 ± 2.5 mmHg (1 slit) and 23.1 ± 8.3 mmHg (3 slits). The IOPs were 23.1 ± 3.1 mmHg and 23.5 ± 4.7 mmHg with 7–0 PDS needles (1 slit and 3 slits, respectively), 21.8 ± 2.2 mmHg and 20.8 ± 4.3 mmHg with 5–0 PDS needles (1 slit and 3 slits, respectively), and with 3–0 PDS needles they were 12.2 ± 3.0 mmHg for one slit and 13.2 ± 3.5 mmHg for 3 slits.Conclusions: Usage of a round (PDS) needles produces more predictable IOP than a spatulated (Vicryl) needle.