A review of aqueous outflow resistance and its relevance to microinvasive glaucoma surgery

Outcomes of Circumferential Versus Hemi-gonioscopy-Assisted Transluminal Trabeculotomy for Congenital Glaucoma

PURPOSE

To compare the efficacy of circumferential gonioscopy-assisted transluminal trabeculotomy (GATT) vs hemi-GATT in primary congenital glaucoma (PCG).

DESIGN

Prospective randomized controlled trial.

METHODS

This study included children with PCG having corneal diameters <14 mm and relatively clear cornea. The eyes included were randomized to undergo either circumferential GATT (360-GATT) or hemi-GATT (180-GATT). The intraocular pressure (IOP) reduction, requirement for glaucoma medications after surgery, need for repeat surgery, and the incidence and type of complications in each group were analyzed. Surgical success was defined as absolute when IOP ≤18 mm Hg (criterion A) and ≤15 mm Hg (criterion B) was achieved without medications and qualified when the same was achieved with pressure-lowering medications. Eyes with an IOP ≥18 mm Hg on maximum medications, those with IOP <6 mm Hg, or need for further intervention for IOP control were considered failures.

RESULTS

Fifty-two eyes of children with PCG were randomized into either the 360-GATT group (22 eyes) or the 180-GATT group (30 eyes) and followed up for at least 1 year. The median follow-up duration was 22.5 months (range: 12-30 months). IOP fell by 49% and 20.5% with 360-GATT and 180-GATT, respectively, with the final IOP being significantly lower in the former group (P = .0003). For absolute success, the cumulative survival was superior with 360-GATT for both criterion A and B at 1 year (P = .009). Average cup-to-disc ratio, corneal diameter, and axial length reversal were significant in the 360-GATT group but not in the 180-GATT group.

CONCLUSIONS

This study reinforces the superior efficacy of circumferential GATT for IOP control in eyes with congenital glaucoma.

A 3D-Printed Aqueous Drainage Tube with an Expandable Inner Diameter to Accommodate the Intraocular Pressure (IOP) Fluctuations After Glaucoma Surgery

Glaucoma treatment involves reducing the intraocular pressure (IOP), which can damage the optic nerve, to a normal range. Aqueous drainage devices may be used for treatment, and a variety of devices have been proposed. However, they have a non-variable and uniform inner diameter, which makes it difficult to accommodate the IOP fluctuations that occur after glaucoma surgery. To ensure effective treatment in the early post-operative period with low IOP and the late post-operative period with high IOP, the inner diameter should be expandable over time to allow for smooth aqueous drainage. Here, we applied 3D printing technology with a tri-axial nozzle to develop an aqueous drainage tube that can expand its inner diameter. The distinct bilayer structure of the device allows it to expand its inner diameter through biodegradation, which can accommodate the IOP fluctuations that often occur after glaucoma surgery. The fabricated structure was evaluated in a series of tests, including leakage, cytotoxicity, and degradation experiments. The device did not show any leakage, was not toxic to cells, and demonstrated the expansion of the inner diameter through biodegradation. The device may provide a more effective post-operative solution for glaucoma patients by alleviating the effects of low IOP in the early post-operative period and high IOP in the late post-operative period.

Bent ab interno needle goniotomy versus gonioscopy-assisted transluminal trabeculotomy in primary open-angle glaucoma: study protocol of a randomized clinical trial

BACKGROUND

Minimally invasive glaucoma surgery (MIGS) is a new class of surgeries, which combines moderate to high success rates and a high safety profile. Bent Ab interno Needle Goniotomy (BANG) and Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) are two low-cost MIGS procedures that communicate the anterior chamber to Schlemm's canal. Most of the available publications on MIGS are either case series or retrospective studies, with different study protocols. The aim of this manuscript is to describe a randomized clinical trial (RCT) protocol to compare the long-term intraocular pressure (IOP) control and the safety of both procedures in eyes with primary open-angle glaucoma.

METHODS

This is a parallel, double-arm, single-masked RCT that includes pseudophakic primary open-angle glaucoma (POAG) eyes. After inclusion criteria, medications will be washed out to verify baseline IOP before surgery. Patients will be randomized to BANG or GATT using a sealed envelope. Follow-up visits will be 1, 7, 15, 30, 60, 90, 180, 330 and 360 days after surgery. On PO330, a new medication washout will be done. The main outcome is the IOP reduction following the procedures. Complimentary evaluation of functional and structural parameters, safety, and quality of life will be done after 30, 90, 180, and 360 days.

DISCUSSION

Our study was designed to compare the long-term efficacy and safety of two low-cost MIGS. Most of the published studies on this subject are case series or retrospective cohorts, with different study protocols, which included different types and severities of glaucomas, combined with cataract extraction. Our study only included mild to moderate POAG eyes, with previous successful cataract extraction. Moreover, it provides a standardized protocol that could be replicated in future studies investigating various types of MIGS. This would allow comparison between different techniques in terms of efficacy, safety, and patients' quality of life.

TRIAL REGISTRATION

Retrospectively registered at the Registro Brasileiro de Ensaios Clínicos (ReBEC) platform RBR-268ms5y . Registered on July 29, 2023. The study was approved by the Ethics Committee of the University of Campinas, Brazil.

Microfluidics in the eye: a review of glaucoma implants from an engineering perspective

Glaucoma is a progressive optic neuropathy in the eye, which is a leading cause of irreversible blindness worldwide and currently affects over 70 million individuals. Clinically, intraocular pressure (IOP) reduction is the only proven treatment to halt the progression of glaucoma. Microfluidic devices such as glaucoma drainage devices (GDDs) and minimally invasive glaucoma surgery (MIGS) devices are routinely used by ophthalmologists to manage elevated IOP, by creating an artificial pathway for the over-accumulated aqueous humor (AH) in a glaucomatous eye, when the natural pathways are severely blocked. Herein, a detailed modelling and analysis of both the natural microfluidic pathways of the AH in the eye and artificial microfluidic pathways formed additionally by the various glaucoma implants are conducted to provide an insight into the causes of the IOP abnormality and the improvement schemes of current implant designs. The mechanisms of representative glaucoma implants have been critically reviewed from the perspective of microfluidics, and we have categorized the current implants into four groups according to the targeted drainage sites of the AH, namely Schlemm's canal, suprachoroidal space, subconjunctival space, and ocular surface. In addition, we propose to divide the development and evolution of glaucoma implant designs into three technological waves, which include microtube (1st), microvalve (2nd) and microsystem (3rd). With the emerging trends of minimal invasiveness and artificial intelligence in the development of medical implants, we envision that a comprehensive glaucoma treatment microsystem is on the horizon, which is featured with active and wireless control of IOP, real-time continuous monitoring of IOP and aqueous rate, etc. The current review could potentially cast light on the unmatched needs, challenges, and future directions of the microfluidic structural and functional designs of glaucoma implants, which would enable an enhanced safety profile, reduced complications, increased efficacy of lowering IOP and reduced IOP fluctuations, closed-loop and on-demand control of IOP, etc.

Effects of Schlemm's Canal Suture Implantation Surgery and Pilocarpine Eye Drops on Trabecular Meshwork Pulsatile Motion

The trabecular meshwork is an important structure in the outflow pathway of aqueous humor, and its movement ability directly affects the resistance of aqueous humor outflow, thereby affecting the steady state of intraocular pressure (IOP). (1) Objective: The purpose of this study was to preliminarily estimate the effects of pilocarpine eye drops and trabeculotomy tunneling trabeculoplasty (3T) on trabecular meshwork (TM) pulsatile motion via phase-sensitive optical coherence tomography (Phs-OCT). (2) Method: In a prospective single-arm study, we mainly recruited patients with primary open-angle glaucoma who did not have a history of glaucoma surgery, and mainly excluded angle closure glaucoma and other diseases that may cause visual field damage. The maximum velocity (MV) and cumulative displacement (CDisp) of the TM were quantified via Phs-OCT. All subjects underwent Phs-OCT examinations before and after the use of pilocarpine eye drops. Then, all subjects received 3T surgery and examinations of IOP at baseline, 1 day, 1 week, 1 month, 3 months, and 6 months post-surgery. Phaco-OCT examinations were performed at 3 and 6 months post-surgery, and the measurements were compared and analyzed. (3) Results: The MV of TM before and after the use of pilocarpine eye drops was 21.32 ± 2.63 μm/s and 17.00 ± 2.43 μm/s. The CDisp of TM before and after the use of pilocarpine eye drops was 0.204 ± 0.034 μm and 0.184 ± 0.035 μm. After the use of pilocarpine eye drops, both the MV and CDisp significantly decreased compared to those before use (p < 0.001 and 0.013, respectively). The IOP decreased from baseline at 22.16 ± 5.23 mmHg to 15.85 ± 3.71 mmHg after 3 months post-surgery and from 16.33 ± 2.51 mmHg at 6 months post-surgery, showing statistically significant differences (p < 0.001). The use of glaucoma medication decreased from baseline at 3.63 ± 0.65 to 1.17 ± 1.75 at 3 months and 1.00 ± 1.51 at 6 months post-surgery; the differences were statistically significant (p < 0.001). Additionally, there was no statistically significant difference in the MV between 3 and 6 months after surgery compared to baseline (p = 0.404 and 0.139, respectively). Further, there was no statistically significant difference in the CDisp between 3 and 6 months after surgery compared to baseline (p = 0.560 and 0.576, respectively) (4) Conclusions: After the preliminary study, we found that pilocarpine eye drops can attenuate TM pulsatile motion, and that 3T surgery may reduce IOP without affecting the pulsatile motion status of the TM.

Outcomes of ab-interno irrigating goniectomy with trabectome in primary and secondary glaucoma from a single center in India

Purpose

This study was done to report intermediate-term outcomes of irrigating goniectomy with trabectome (trabectome) surgery among different types of glaucoma eyes from a single center in India using a cross-sectional, longitudinal, observational study design.

Methods

Fifty-three patients (58 eyes) with glaucoma who underwent irrigating goniectomy with trabectome between January 2019 and February 2020 were included. Pre-operative data included age, gender, eye laterality, specific diagnosis, number of anti-glaucoma medications (AGMs), prior glaucoma surgeries, visual acuity, and intraocular pressure (IOP) on medical treatment. Post-operative data included IOP changes during the follow-up till 1-year, number of AGMs, any complications, or additional surgical intervention required. Success was defined as IOP ≤ 21 mmHg and ≥ 20% reduction of IOP from pre-operative IOP with no additional glaucoma surgery.

Results

The cohort included 58 eyes (male 53.4% and female 46.6%) ranging from 0.6 to 81 years of age. The average baseline IOP was 23.4 ± 10.2 mmHg and reduced significantly with surgery to 14.1 ± 5.3 mmHg at 1-year follow-up. The AGMs reduced from 2.4 ± 1.4 pre-surgery to 1.6 ± 1.4 at 1-year follow-up. Four eyes required additional glaucoma surgeries for IOP control. The success rate of trabectome with phacoemulsification (88%) was discernibly higher than with trabectome alone (67%). Intra-operatively, significant blood reflux was noticed in 27 eyes, of which only one required tamponading with a viscoelastic agent.

Conclusion

This study concludes that irrigating goniectomy with trabectome has good efficacy and safety in both pediatric and adult cases of glaucoma in terms of IOP control, reduction in AGMs, and low incidence of complications in the Indian population.

Ciliochoroidal effusion and its association with the outcomes of micropulse transscleral laser therapy in glaucoma patients: a pilot study

We investigate the development of ciliochoroidal effusion following micropulse transscleral laser therapy (MPTLT) and evaluate the relationship between the early postoperative ciliochoroidal effusion (ECE) and short-term treatment outcomes. Glaucoma patients who underwent MPTLT were assessed for ciliochoroidal effusion by anterior segment optical coherence tomography (AS-OCT) at postoperative 1, 4, 12 weeks. The subjects were classified based on AS-OCT findings at postoperative 1 week into eyes with and without ECE. The absolute intraocular pressure (IOP), IOP reduction and number of antiglaucoma medications were compared between eyes with and without ECE. A total of 50 eyes were included, of which 23 (46%) developed ciliochoroidal effusion at postoperative 1 week. Almost all effusion resolved at 4 weeks. At 12 weeks, the mean IOP (SD) significantly decreased from 28.5 (12.8) mmHg to 17.8 (10.5) mmHg (p < 0.001), and the mean number of medications (SD) decreased from 4.1 (0.9) to 3.3 (1.1) (p < 0.001). Eyes with ECE had significantly greater IOP reduction (p = 0.009) and lower absolute IOP (p = 0.008) at the 4-week visit. There was no significant difference in number of medications between the groups. In conclusion, ciliochoroidal effusion was commonly observed following MPTLT. Eyes with ECE had overall greater IOP reduction during early post-operation.

Selective Laser Trabeculoplasty and Outcomes of Subsequent Phacoemulsification Combined with Kahook Dual Blade Goniotomy

Introduction

To investigate the relationship between intraocular pressure (IOP)-lowering success of selective laser trabeculoplasty (SLT) and combined phacoemulsification/Kahook Dual Blade (phaco/KDB) goniotomy in eyes with mild to severe open angle glaucoma (OAG).

Methods

Eyes undergoing combined phaco/KDB goniotomy and that had previously undergone SLT were analyzed. Data collected included demographics, glaucoma type and severity, IOP, and topical IOP-lowering medications before and after both procedures. Eyes were divided into two groups based on success of SLT, defined as IOP reduction of at least 20% maintained on at least two consecutive follow-up visits without any subsequent medication additions or interventions. Phaco/KDB goniotomy success was defined as IOP reduction of at least 20% and/or reduction in the number of IOP-lowering medications of at least one up to 12 months of follow-up.

Results

Overall, SLT was successful in 20 of 43 eyes (46.5%), of which 63.6% (7/11) had successful phaco/KDB goniotomy at 12 months follow-up. Among eyes with unsuccessful SLT, 60.0% (9/15) had successful phaco/KDB at 12 months follow-up. Phaco/KDB success rate was similar in patients regardless of their previous response to SLT at all postoperative time points up to 12 months follow-up (p = 0.87).

Conclusions

The presence or lack of IOP-lowering response to SLT did not influence the success rate of subsequent phaco/KDB goniotomy in eyes with mild to severe OAG. Patients who did not respond to SLT still benefited from phaco/KDB goniotomy at a later date.

Bionic eye system mimicking microfluidic structure and intraocular pressure for glaucoma surgery training

Among increasing eye diseases, glaucoma may hurt the optic nerves and lead to vision loss, the treatment of which is to reduce intraocular pressure (IOP). In this research, we introduce a new concept of the surgery simulator for Minimally Invasive Glaucoma Surgery (MIGS). The concept is comprised of an anterior eye model and a fluidic circulatory system. The model made of flexible material includes a channel like the Schlemm’s canal (SC) and a membrane like the trabecular meshwork (TM) covering the SC. The system can monitor IOP in the model by a pressure sensor. In one of the MIGS procedures, the TM is cleaved to reduce the IOP. Using the simulator, ophthalmologists can practice the procedure and measure the IOP. First, considering the characteristics of human eyes, we defined requirements and target performances for the simulator. Next, we designed and manufactured the prototype. Using the prototype, we measured the IOP change before and after cleaving the TM. Finally, we demonstrated the availability by comparing experimental results and target performances. This simulator is also expected to be used for evaluations and developments of new MIGS instruments and ophthalmic surgery robots in addition to the surgical training of ophthalmologists.

Rational Design of Microfluidic Glaucoma Stent

Glaucoma is a common, irreparable eye disease associated with high intraocular pressure. One treatment option is implantation of a stent to lower the intraocular pressure. A systematic approach to develop a microchannel stent meshwork that drains aqueous humor from the anterior chamber of the eye into the subconjunctival space is presented. The stent has a large number of outlets within its mesh structure that open into the subconjunctiva. The development approach includes a flow resistance model of the stent. Local adaption of the stent’s tubular dimensions allows for adjustment of the flow resistance. In this way, an evenly distributed outflow into the subconjunctiva is achieved. We anticipate that microblebs will form at the stent outlets. Their size is crucial for drainage and control of intraocular pressure. An analytical model for bleb drainage is developed based on the porous properties of the subconjunctival tissue. Both models—the stent flow resistance model and the bleb drainage model—are verified by numerical simulation. The models and numerical simulation are used to predict intraocular pressure after surgery. They allow for a systematic and personalized design of microchannel stents. Stents designed in this way can stabilize the intraocular pressure between an upper and lower limit.

Gonioscopy-Assisted Transluminal Trabeculotomy for Glaucoma: 1-Year Outcomes and Success Predictors

PRCIS

Our results suggest gonioscopy-assisted transluminal trabeculotomy (GATT) as an effective and safe option for the surgical management of open-angle glaucoma (OAG). Older age was the only risk factor for failure in our analysis.

PURPOSE

To report 12-month clinical outcomes, safety profile and success predictors of GATT in patients with OAG.

PATIENTS AND METHODS

A retrospective study of patients (18 y old and above) with medically uncontrolled OAG who underwent GATT as a solo procedure or combined with phacoemulsification (PHACO-GATT) between January 2018 and January 2020. Success at 12 months (primary outcome) was defined as intraocular pressure (IOP) <15 mm Hg, with an IOP reduction of at least 20%, OR a reduction of at least 2 glaucoma medications, compared with baseline. Secondary outcomes were success predictors and safety parameters.

RESULTS

A total of 73 eyes (GATT=38; PHACO-GATT=35) from 58 patients with a mean age of 54.8±11.6 years were included. Overall, after 12 months of follow-up, the mean IOP was reduced from 24.9±8.5 to 12.1±2.1 mm Hg (P<0.001). The mean number of glaucoma medications was reduced from 3.5±0.7 to 1.2±1.2 (P<0.001). The success rate was 87% at 12 months, with no significant differences between GATT (85%) and PHACO-GATT (91%) eyes (P=0.330). Age was the only factor significantly associated with surgical success (hazard ratio=1.35; P=0.012; after adjusting for preoperative IOP and number of glaucoma medications). Patients older than 60 years had a significant greater chance of failure (hazard ratio=10.96; P=0.026) compared with those younger than 60 years. The most common postoperative complication was transient hyphema (39%; median duration, 5 d). No sight-threatening adverse event was documented.

CONCLUSIONS

GATT was effective and safe at lowering IOP with or without cataract extraction in OAG. Patients 60 years or older had a higher risk of failure compared with those younger in age.

Modeling the Effects of Disease, Drug Properties, and Material on Drug Transport From Intraocular Lenses

Purpose

Surgically implanted intraocular lenses (IOLs) may be used as drug-delivery devices, but their effectiveness is not well defined. Computational fluid dynamics models were developed to investigate the capability of IOLs to release drugs at therapeutic concentrations.

Methods

Models were generated using COMSOL Multiphysics. Primary open-angle glaucoma (POAG) and wet age-related macular degeneration (AMD) were simulated by reducing aqueous vein and choroidal blood flow, respectively. Release of dexamethasone, ganciclovir, or dextran was studied using common IOL materials, polydimethylsiloxane (PDMS) and poly(2-hydroxyethyl methacrylate) (PHEMA).

Results

Drug clearance proceeds mainly through choroidal blood flow. When fully constricted, maximum concentration at the choroid (Cmax) values increased by 32.4% to 39,800%. Compared to dexamethasone, Cmax in different tissues decreased by 6.07% to 96.0% for ganciclovir and dextran, and clearance rates decreased by 16% to 69% for ganciclovir and by 92% to 100% for dextran. Using PDMS as the IOL reduced clearance rates by 91.3% to 94.6% compared to PHEMA.

Conclusions

In diseased eyes, drugs accumulate mainly in posterior tissue; thus, choroidal drug toxicity must be assessed prior to IOL implantation in POAG and AMD patients. Moreover, drug properties modulated concentration profiles in all ocular segments. The hydrophobic small-molecule dexamethasone attained the highest concentrations and cleared the fastest, whereas hydrophilic macromolecular dextran attained the lowest concentrations and cleared the slowest. Furthermore, high concentrations were achieved quickly following release from PHEMA, whereas PDMS allowed for sustained release.

Translational Relevance

In silico results can guide scientists and clinicians regarding important physiological and chemical factors that modulate tissue drug concentrations from drug-eluting IOLs.

The surgical management of glaucoma: A review

After a long period of little change, glaucoma surgery has experienced a dramatic rise in the number of possible procedures in the last two decades. Glaucoma filtering surgeries with mitomycin C and glaucoma drainage devices remain the standard of surgical care. Other newer surgeries, some of which are minimally or microinvasive glaucoma surgeries, target existing trabecular outflow, enhance suprachoroidal outflow, create subconjunctival blebs, or reduce aqueous production. Some require the implantation of a device such as the iStent, Hydrus, Ex-PRESS, XEN and PRESERFLO, whilst others do not-Trabectome, Kahook dual blade, Ab interno canaloplasty, gonioscopy-assisted transluminal trabeculotomy, OMNI and excimer laser trabeculotomy. Others are a less destructive variation of an established procedure, such as micropulse transscleral cyclophotocoagulation, endoscopic cyclophotocoagulation and ultrasound cycloplasty. Cataract surgery alone can be a significant glaucoma operation. These older and newer glaucoma surgeries, their mechanism of action, efficacy and complications are the subject of this review.

Conventional glaucoma implants and the new MIGS devices: a comprehensive review of current options and future directions

Glaucoma is a progressive optic neuropathy that is the second leading cause of preventable blindness worldwide, after cataract formation. A rise in the intraocular pressure (IOP) is considered to be a major risk factor for glaucoma and is associated with an abnormal increase of resistance to aqueous humour outflow from the anterior chamber. Glaucoma drainage devices have been developed to provide an alternative pathway through which aqueous humour can effectively exit the anterior chamber, thereby reducing IOP. These devices include the traditional aqueous shunts with tube-plate design, as well as more recent implants, such as the trabeculectomy-modifying EX-PRESS^® implant and the new minimally invasive glaucoma surgery (MIGS) devices. In this review, we will describe each implant in detail, focusing on their efficacy in reducing IOP and safety profile. Additionally, a critical and evidence-based comparison between these implants will be provided. Finally, we will propose potential developments that may help to improve the performance of current devices.

Twelve-month results of ab interno trabeculectomy with Kahook Dual Blade: an interventional, randomized, controlled clinical study

PURPOSE

To evaluate the efficacy and safety profile of Kahook Dual Blade ab interno trabeculectomy combined with phacoemulsification compared to stand-alone conventional cataract surgery.

METHODS

A single-center longitudinal, randomized controlled trial was conducted. Patients older than 18 years with coexisting cataract and open-angle glaucoma or ocular hypertension were invited to participate. Preoperative and postoperative clinical data were collected and analyzed preoperatively and at months 1, 3, 6, and 12 after the procedure. Main outcome measures included best corrected visual acuity, intraocular pressure, number of glaucoma medications, endothelial cell count, and standard automated perimetry.

RESULTS

Forty-two eyes from 33 patients were randomly allocated to the combined cataract and KDB (treatment, n = 21) or cataract alone (control, n = 21) groups. Intraocular pressure decreased from 17.9 ± 3.5 to 16.0 ± 2.2 mmHg and from 17.3 ± 2.5 to 15 ± 3.2 mmHg at the last visit in the treatment and control groups (p = 0.47). The use of glaucoma medications was reduced from a median (IQR) 1 (1-2) to 0 (0-0) in the treatment group and from 1 (1-2) to 0 (0-1) in the control group, with no significant differences between groups at the 12-month visit (p = 0.47). Best corrected visual acuity, endothelial cell count, and standard automated perimetry remained similar during follow-up in both groups.

CONCLUSIONS

In patients with well-controlled, mild-to-moderate glaucoma, adding ab interno trabeculectomy with KDB to phacoemulsification might not be more effective than phacoemulsification alone to reach mid-teens IOP values. Both procedures showed similar safety profiles.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04202562, December 17, 2019 retrospectively registered.

Relationship between selective laser trabeculoplasty and excisional goniotomy outcomes in glaucomatous eyes

OBJECTIVE

To evaluate the relationship between intraocular pressure (IOP)-lowering success with selective laser trabeculoplasty (SLT) and Kahook Dual Blade (KDB) goniotomy in eyes with glaucoma.

DESIGN

Retrospective chart review.

PARTICIPANTS

30 eyes of 24 patients undergoing phacoemulsification combined with a KDB with 6 months follow-up and who had previously undergone SLT in the same eye.

METHODS

Data collected from electronic health records included demographic and glaucoma status, IOP and IOP-lowering medication after SLT and KDB. SLT and KDB success were defined as IOP reduction ≥20% or medication reduction ≥1 at 2 and 6 months, respectively.

MAIN OUTCOME

Association between SLT success and KDB success.

RESULTS

Overall, SLT was successful in 17 of 30 eyes (56.7%) at 2 months, and KDB was successful in 18 of 30 eyes (60%) at 6 months. Nine of 17 eyes (52.9%) with prior successful SLT had successful subsequent KDB, whereas 9 of 13 (69.2%) with prior unsuccessful SLT had successful KDB. There was no significant relationship between SLT and KDB outcome in these 30 eyes (p = 0.465 by Fisher's exact test).

CONCLUSION

No relationship between success of SLT and subsequent KDB was observed. However, patients with history of failed SLT still benefited from subsequent KDB.

Factors Associated With Unqualified Success After Trabecular Bypass Surgery: A Case-control Study

PRECIS

An older age, a low number of baseline glaucoma medications, an early glaucoma stage, lower intraocular pressure (IOP) values during the first postoperative month, and combined surgery are possible predictors of unqualified success after a trabecular by-pass microinvasive glaucoma surgery (MIGS) procedure.

PURPOSE

The purpose of this study was to identify the potential predictors of unqualified success (IOP<18 mm Hg with no glaucoma medication) after trabecular by-pass MIGS.

MATERIALS AND METHODS

We designed a case-control study using logistic regression modeling that included all trabecular by-pass surgeries with at least 3 months of follow-up, performed at a single center from June 2017 to December 2019. Eyes that achieved an endpoint of unqualified success (dependent variable) were considered cases. All other eyes were used as the controls. Cases and controls were paired by sex and postoperative time. We tested the following independent variables: age, race, laterality (right eye or left eye), glaucoma stage, type of surgery (combined or stand-alone), type of trabecular bypass, intraoperative complications, baseline number of medications, baseline IOP, and postoperative IOP on days 1, 15, and 30. Additional analysis using IOP <15 mm Hg as a threshold and including eyes with at least 12 months of follow-up were performed.

RESULTS

One hundred ninety-four eyes were included in the analysis. We observed complete success in 56.7% of eyes. The mean follow-up time for the entire population was 12.3±6.8 months. All variables were considered in the first step of the modeling process; however, only age, day-15 IOP, day-30 IOP, baseline number of medications, glaucoma stage, and type of surgery remained until the completion of our model, with adequate significance (P<0.05). The additional analysis confirmed our results.

CONCLUSION

We identified that an older age, a low number of baseline glaucoma medications, an early glaucoma stage, lower IOP values during the first postoperative month, and combined surgery were associated with a higher chance of unqualified success at 12 months after a trabecular by-pass MIGS procedure.

Low expression of GSTP1 in the aqueous humour of patients with primary open-angle glaucoma

Primary open‐angle glaucoma (POAG) is characterized by irreversible neurodegeneration accompanied by visual field defects and high intraocular pressure. Currently, an effective treatment is not available to prevent the progression of POAG, other than treatments to decrease the high intraocular pressure. We performed proteomic analysis of aqueous humour (AH) samples from patients with POAG combined with cataract and patients with cataract to obtain a better understanding of the pathogenesis of POAG and explore potential treatment targets for this condition. Samples were collected from 10 patients with POAG combined with cataract and 10 patients with cataract. Samples from each group were pooled. A high‐resolution, label‐free, liquid chromatography‐tandem mass spectrometry‐based quantitative proteomic analysis was performed. In total, 610 proteins were identified in human AH samples from the two groups. A total of 48 up‐regulated proteins and 49 down‐regulated proteins were identified in the POAG combined with cataract group compared with the control group. Gene Ontology (GO) analysis revealed key roles for these proteins in inflammation, immune responses, growth and development, cellular movement and vesicle‐mediated transport in the biological process category. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated the down‐regulated expression of glutathione S‐transferase P (GSTP1) in the glutathione metabolism signalling pathway in the POAG combined with cataract group. Additionally, certain significantly differentially expressed proteins in the proteomic profile were verified by enzyme‐linked immunosorbent assay (ELISA). GSTP1 levels were reduced in the human AH samples from the POAG combined with cataract group, based on the results of ELISA and proteomic profiling. Therefore, GSTP1, a redox‐related marker, may be involved in the pathological process of POAG and may become a treatment target in the future.

iStent Inject (Second-generation Trabecular Microbypass) Versus Nonpenetrating Deep Sclerectomy in Association With Phacoemulsification for the Surgical Treatment of Open-angle Glaucoma and Cataracts: 1-Year Results

PRECIS

Both nonpenetrating deep sclerectomy (NPDS) and iStent inject are safe and effective when combined with phacoemulsification. The NPDS group presented lower final intraocular pressure (IOP); however, more postoperative intervention and longer recovery time was required.

AIM

The aim of this study was to assess the 1-year efficacy and safety of second-generation trabecular microbypass stent implantation (iStent inject) versus NPDS in association with phacoemulsification (Phaco) for the concomitant surgical treatment of open-angle glaucoma and cataracts.

MATERIALS AND METHODS

This was a single-center longitudinal retrospective comparative study of eyes treated with Phaco-NPDS, with adjunctive use of collagen matrix implant and mitomycin C (group 1), or Phaco-iStent inject (group 2). The main outcome measures were success rates [absolute success: proportion of eyes with IOP<18 mm Hg without any glaucoma medication; relative success: proportion of eyes achieving different target IOPs (<18; <15; and <12 mm Hg) with or without medication]; mean reduction (%) in IOP and medication use; number of postoperative reinterventions (goniopuncture, needling, and reoperation); and number of complications.

RESULTS

The mean age (y) was 69.3 in group 1 and 72.7 in group 2. Groups 1 (n=51) and 2 (n=32) achieved absolute success rates of 74.5% and 81.3%, respectively (P=0.333). Concerning relative success rates, no significant difference was found for IOP<18 mm Hg or an IOP<15 mm Hg between the 2 groups. However, significantly more eyes achieved an IOP <12 mm Hg in the Phaco-NPDS group. The mean percentage of IOP reduction from baseline to the end of follow-up was also statistically higher in group 1 (39.9% vs. 24.5%). Both groups achieved similar results in the mean reduction of medications per eye. No significant complications were found in either group, but patients in group 1 required more postoperative intervention than group 2.

CONCLUSIONS

Both techniques are safe and effective for the concomitant surgical treatment of open-angle glaucoma and cataracts and presented comparable relative success rates at different target IOP levels (<18 and <15 mm Hg). A larger proportion of patients in group 1 achieved a target IOP <12 mm Hg; however, more postoperative intervention was required.

Aqueous Humor Outflow Requires Active Cellular Metabolism in Mice

Purpose

Conventional wisdom posits that aqueous humor leaves the eye by passive bulk flow without involving energy-dependent processes. However, recent studies have shown that active processes, such as cell contractility, contribute to outflow regulation. Here, we examine whether inhibiting cellular metabolism affects outflow facility in mice.

Methods

We measured outflow facility in paired enucleated eyes from C57BL/6J mice using iPerfusion. We had three Experimental Sets: ES1, perfused at 35°C versus 22°C; ES2, perfused with metabolic inhibitors versus vehicle at 35°C; and ES3, perfused at 35°C versus 22°C in the presence of metabolic inhibitors. Inhibitors targeted glycolysis and oxidative phosphorylation (2-deoxy-D-glucose, 3PO and sodium azide). We also measured adenosine triphosphate (ATP) levels in separate murine anterior segments treated like ES1 and ES2.

Results

Reducing temperature decreased facility by 63% [38%, 78%] (mean [95% confidence interval (CI)], n = 10 pairs; P = 0.002) in ES1 after correcting for changes in viscosity. Metabolic inhibitors reduced facility by 21% [9%, 31%] (n = 9, P = 0.006) in ES2. In the presence of inhibitors, temperature reduction decreased facility by 44% [29%, 56%] (n = 8, P < 0.001) in ES3. Metabolic inhibitors reduced anterior segment adenosine triphosphate (ATP) levels by 90% [83%, 97%] (n = 5, P<<0.001), but reducing temperature did not affect ATP.

Conclusions

Inhibiting cellular metabolism decreases outflow facility within minutes. This implies that outflow is not entirely passive, but depends partly on energy-dependent cellular processes, at least in mice. This study also suggests that there is a yet unidentified mechanism, which is strongly temperature-dependent but metabolism-independent, that is necessary for nearly half of normal outflow function in mice.

Minimally Invasive Surgery, Implantable Sensors, and Personalized Therapies

Glaucoma management has changed dramatically over the last decades, through clinical advances and technological revolutions. This review discusses the latest innovations and challenges faced in the field around three major axes: minimally-invasive glaucoma surgery (MIGS), implantable sensors and injectable therapeutics. Indeed, the vast number of recently developed MIGS techniques has not only provided clinicians with a wide range of therapeutic options, but they have also enabled them to adjust their therapies more finely which may have contributed a more patient-centric decision-making process. Yet, despite considerable advances in the field, the wide heterogeneity in clinical trial designs blurs the surgical outcomes, specificities and indications. Thus, more high-quality data are required to make the choice of a specific MIGS procedure more than an educated guess. Beyond the scope of MIGS, the potential of IOP telemetry for self-assessment of IOP-control through implantable sensors is developing into a real option for clinicians and an empowering opportunity for patients. Indeed, providing patients with direct feedback enables them to take control and have a clearer representation of their care, in turn leading to a better control of the disease. However, there are potential issues with self-monitoring of IOP, such as increased anxiety levels induced by measured IOP fluctuations and peaks, leading to patients self-treating during IOP spikes and additional office visits. Furthermore, the advent of implantable therapeutics may soon provide yet another step towards personalized glaucoma treatment, by offering not only an efficient alternative to current treatments, but also a therapeutic option that may better adapt to patients' lifestyle. After several decades of relative stagnation through the last century, glaucoma has now entered what many view as a golden age for the specialty. Like every revolution, this one brings its fair share of uncertainty, clinical questioning and uneasy periods of adaptation to ever-changing expectations. Yet, while it is impossible to guess what the landscape of glaucoma surgery will be like in ten or fifteen years, data suggest a bright outlook both for patients and clinicians.

[The trabecular meshwork: Structure, function and clinical implications. A review of the littérature (French translation of the article)]

Glaucoma is a blinding optic neuropathy, the main risk factor for which is increased intraocular pressure (IOP). The trabecular meshwork, located within the iridocorneal angle, is the main pathway for drainage of aqueous humor (AH) out of the eye, and its dysfunction is responsible for the IOP elevation. The trabecular meshwork is a complex, fenestrated, three-dimensional structure composed of trabecular meshwork cells (TMC) interdigitated into a multilayered organization within the extracellular matrix (ECM). The purpose of this literature review is to provide an overview of current understanding of the trabecular meshwork and its pathophysiology in glaucoma. Thus, we will present the main anatomical and cellular bases for the regulation of aqueous humor outflow resistance, the pathophysiological mechanisms involved in trabecular dysfunction in the various types of glaucoma, as well as current and future therapeutic strategies targeting the trabecular meshwork.

Aqueous Angiography in Normal Canine Eyes

Purpose

To conduct aqueous angiography (AA) using a clinically applicable technique in normal dogs and to compare findings to intravenous scleral angiography (SA).

Methods

We examined 10 canine cadaver eyes and 12 eyes from live normal dogs. A gravity-fed trocar system delivered 2% sodium fluorescein and 0.25% indocyanine green (ICG) intracamerally (IC) in cadaver eyes. In vivo AA was subsequently performed in one eye of each of the 12 dogs via IC bolus of ICG under sedation. The same 12 dogs received SA via intravenous ICG (mean ± SD) 10.7 ± 3.3 days later. Identical scleral sectors were imaged using a Spectralis confocal scanning laser ophthalmoscope.

Results

The gravity-fed trocar system permitted visualization of the conventional aqueous humor outflow (CAHO) pathways in cadaver eyes, but not in vivo. Fluorescence was observed superonasally in four of the 10 cadaver eyes within 24.0 ± 3.6 seconds. A single IC bolus of ICG showed CAHO pathways in vivo, demonstrating sectoral outflow patterns in the superotemporal sclera in 10 of the 12 eyes within 35.0 ± 4.3 seconds; four of the 12 eyes exhibited pulsatile aqueous movement. SA exhibited fluorescence patterns comparable to AA with weak pulsatile aqueous humor outflow.

Conclusions

Angiography (AA or SA) in dogs permits visualization of the CAHO pathway and its vascular components in vivo. AA may be a more useful modality to assess aqueous humor outflow.

Translational Relevance

Intracameral AA has potential utility for evaluating CAHO in vivo in dogs, an important animal model species.

The trabecular meshwork: Structure, function and clinical implications. A review of the literature

Glaucoma is a blinding optic neuropathy, the main risk factor for which is increased intraocular pressure (IOP). The trabecular meshwork, located within the iridocorneal angle, is the main pathway for drainage of aqueous humor (AH) out of the eye, and its dysfunction is responsible for the IOP elevation. The trabecular meshwork is a complex, fenestrated, three-dimensional structure composed of trabecular meshwork cells (TMC) interdigitated into a multilayered organization within the extracellular matrix (ECM). The purpose of this literature review is to provide an overview of current understanding of the trabecular meshwork and its pathophysiology in glaucoma. Thus, we will present the main anatomical and cellular bases for the regulation of aqueous humor outflow resistance, the pathophysiological mechanisms involved in trabecular dysfunction in the various types of glaucoma, as well as current and future therapeutic strategies targeting the trabecular meshwork.

Minimally Invasive Glaucoma Surgery: Where Is the Evidence?

PURPOSE

The last decade has witnessed an unprecedented growth in glaucoma treatment options through the introduction of minimally invasive glaucoma surgeries (MIGS). The aim of the present review is to provide an understanding of the currently available MIGS and to examine what data are currently available to guide treatment choice.

DESIGN

Meta-analysis and systematic review of randomized and non-randomized control trials.

METHODS

Out of 2567 articles identified, a total of 77 articles were retained for analysis, including 28 comparative studies and 12 randomized control trials. Overall, 7570 eyes were included. When data permitted, the weighted mean difference in intraocular pressure reduction was calculated for comparison purposes.

RESULTS

Weighted mean intraocular pressure reductions from all analyzed studies were: 15.3% (iStent), 29.1% (iStent inject), 36.2% (ab interno canaloplasty), 34.4% (Hydrus), 36.5% (gonioscopically-assisted transluminal trabeculotomy), 24.0% (trabectome), 25.1% (Kahook dual blade), 30.2% (Cypass), 38.8% (XEN), and 50.0% (Preserflo).

CONCLUSIONS

One of the advantages of the heterogenous range of available MIGS options is the chance to tailor therapy in an individualized manner. However, high-quality data are required to make this choice more than an educated guess. Overall, this review confirms the efficiency of assessed MIGS compared with standalone phacoemulsification, but it highlights that only few studies compare different MIGS techniques and even fewer assess MIGS against criterion standard treatments. Current evidence, while non-negligible, is mostly limited to heterogenous nonrandomized studies and uncontrolled retrospective comparisons, with few quality randomized control trials. We suggest that future research should be comparative and include relevant comparators, standardized to report key outcome features, long-term to assess sustainability and late complications, and ideally randomized.

Effectiveness and Safety of Long Duration versus Short Duration Diode Laser Transscleral Cyclophotocoagulation

Purpose

To compare the efficacy and safety of diode laser transscleral cyclophotocoagulation using either the long duration or short duration protocol.

Methods

Retrospective series of 23 consecutive patients with glaucoma who underwent continuous-wave diode laser transscleral cyclophotocoagulation from August 2016 to July 2018 at a tertiary hospital in Hong Kong. Laser pulse duration for the long and short duration protocols was defined as 3.0–4.0 and 1.5–2.0 s, respectively.

Results

There were 15 male and 8 female Chinese subjects (23 eyes), age 49–90 (71.3 ± 2.7), with 10 subjects that underwent long duration cyclophotocoagulation (power 1239.2 ± 78.3 mW, spots 13.9 ± 1.4) and 13 subjects that had short duration cyclophotocoagulation (mean power 1817.3 ± 85.7 mW, spots 14.4 ± 1.0). Six months after long and short duration cyclophotocoagulation, intraocular pressure decreased significantly from 29.9 ± 7.8 to 21.1 ± 6.5 (p < 0.01), and from 35.4 ± 2.7 to 24.1 ± 3.4 (p = 0.04), respectively, while glaucoma medications decreased significantly by 1.4 ± 0.5 (p = 0.02) in the long duration group only. Reduction of medications after short duration cyclophotocoagulation was less and did not reach statistical significance (0.9 ± 0.9, p = 0.15). There was no significant difference of visual deterioration and complication rates.

Conclusion

Both types of cyclophotocoagulation were equally effective in lowering intraocular pressure by 6 months, but the short duration protocol, using higher laser power, was able to achieve a greater and earlier reduction, at 3 months. However, the long duration protocol, using less laser power, appears better at reducing medication requirement by 6 months.