Rapid learning curve assessment in an ex vivo training system for microincisional glaucoma surgery

Learning Curve in Posterior Segment Ophthalmic Diagnostic Endoscopy: Implications for Budding Enthusiasts and Fellows-In-Training

PURPOSE

To elucidate the learning curve for posterior segment diagnostic endoscopy (DE) based on the results of a self-trained (ST) and a supervised (SUP) vitreoretinal surgeon.

METHODS

Retrospective review of medical records of DE performed between 2017 and 2023 by one ST and one SUP vitreoretinal surgeon at a tertiary eye care institute. Data were collected and the serial number of cases was plotted against the time taken for the procedure. A comparative regression plot was created for both the surgeons to know the slope of the learning curve. The start time was noted as that of attachment of the endoscope and the stop time was noted as the end of diagnostic evaluation. Procedures were divided into blocks of 10 cases each and the time taken for the procedures was calculated.

RESULTS

Total of 106 eyes (58 by ST surgeon and 48 by SUP surgeon) were included. For ST surgeon, the time taken for the surgery correlated inversely (reduced sequentially) with the serial number of the case till the 20th case (correlation coefficient = -0.5, p = .01), for SUP surgeon, the time taken for the surgery correlated inversely with the serial number of the case till the 10th case (correlation coefficient = -0.9, p = <0.0001) and then stabilized. Neither of the groups had any adverse events.

CONCLUSION

About 20 cases for a self-trained and about 10 cases for a supervised vitreoretinal surgeon are required to get stable with DE. These observations have implications in creating a training module for DE with appropriate number of training cases.

Prospective Study of Canaloplasty and Trabeculotomy Performed by Trainees

Purpose

To evaluate outcomes of new adopters of the OMNI® Surgical System (Sight Sciences, Inc.) by prospectively evaluating intermediate-term outcomes of patients operated by trainees.

Patients and Methods

This was a prospective study of surgeries performed by trainees on patients with open angle glaucoma undergoing simultaneous cataract surgery and ab interno canaloplasty and trabeculotomy using the OMNI Surgical System. Pre-operative intraocular pressure (IOP) and number of glaucoma medications were recorded. Only patients with a minimum of 6-month follow up were included. Baseline IOP was used to separate subjects into two groups: Group 1 (IOP ≥18 mmHg) and Group 2 (IOP <18 mmHg). Mean decrease in IOP and medications was calculated and compared with paired t-tests for the overall sample as well as the subgroups. Success was defined as those with a ≥20% reduction from pre-operative IOP or with an IOP ≤18 mmHg and ≥6 mmHg and on the same or fewer number of medications while not requiring additional surgery. Adverse events were also recorded.

Results

Forty-two eyes of 31 patients were included. Mean pre-operative IOP was 17.2 ± 4.8 mmHg and mean number of medications was 2.4 ± 1.2. The primary endpoint was reached in 83.3% of patients at 12 months. IOP was reduced by 22.3% to 13.4 ± 2.4 (p<0.001). Mean number of medications decreased to 1.7 ± 1.6 (p<0.001). Group 1 mean IOP decreased 35.4% from 22.2 ± 4.6 mmHg to 14.3 ± 2.8 mmHg (p<0.001). Group 2 mean number of medications decreased from 2.3 ± 1.1 to 1.6 ± 1.5 (p<0.001).

Conclusion

When operated on by the novice MIGS surgeon, the OMNI device provides effective IOP and glaucoma medication reduction with minimal adverse events. Efficacy and safety of the device in the hands of trainees was comparable to experienced glaucoma surgeons suggesting its ease of adoption.

Tissue-engineered anterior segment eye cultures demonstrate hallmarks of conventional organ culture

BACKGROUND

Glaucoma is a blinding disease largely caused by dysregulation of outflow through the trabecular meshwork (TM), resulting in elevated intraocular pressure (IOP). We hypothesized that transplanting TM cells into a decellularized, tissue-engineered anterior segment eye culture could restore the outflow structure and function.

METHODS

Porcine eyes were decellularized with freeze-thaw cycles and perfusion of surfactant. We seeded control scaffolds with CrFK cells transduced with lentiviral vectors to stably express eGFP and compared them to scaffolds seeded with primary TM cells as well as to normal, unaltered eyes. We tracked the repopulation behavior, performed IOP maintenance challenges, and analyzed the histology.

RESULTS

Transplanted cells localized to the TM and progressively infiltrated the extracellular matrix, reaching a distribution comparable to normal, unaltered eyes. After a perfusion rate challenge to mimic a glaucomatous pressure elevation, transplanted and normal eyes reestablished a normal intraocular pressure (transplanted = 16.5 ± 0.9 mmHg, normal = 16.9 ± 0.9). However, eyes reseeded with eGFP-expressing CrFK cells could not regulate IOP, remaining high and unstable (27.0 ± 6.2 mmHg) instead.

CONCLUSION

Tissue-engineered anterior segment scaffolds can serve as readily available, scalable ocular perfusion cultures. This could reduce dependency on scarce donor globes in outflow research and may allow engineering perfusion cultures with specific geno- and phenotypes.

Surgeon Experience as a Risk Factor for Short-Term Failure for Ab Interno Gelatin Microstent: A Canadian Multicenter Propensity-Matched Study

PURPOSE

To compare the efficacy and safety of early versus later ab interno gelatin microstent placement with mitomycin C.

DESIGN

Canada-wide, multicenter, retrospective propensity score-matched cohort study.

PARTICIPANTS

Two hundred seventy eyes (135 early cases and 135 later cases) with no prior incisional surgery.

METHODS

Surgeons' first 20 patients (early cases group), from 6 glaucoma surgeons across 4 Canadian sites, were matched 1:1 to patients with the closest propensity score from the later (21+) patients (later cases group).

MAIN OUTCOME MEASURES

Primary outcome was hazard ratio (HR) of failure of the early versus later cases groups, with failure defined as IOP of less than 6 mmHg with more than 2 lines of vision loss or more than 17 mmHg with no medications (complete success) on 2 consecutive visits despite in-clinic maneuvers (including needling) more than 1 month after surgery. Secondary outcomes were HRs for failure, defined as IOP outside the range of 6 to 14 mmHg and 6 to 21 mmHg with and without allowing for medications (qualified success), interventions, complications, and reoperations.

RESULTS

Hazard ratio of failure for early versus later cases groups was 1.38 (95% confidence interval [CI], 0.97-1.96) for the IOP range of 6 to 17 mmHg, 1.29 (95% CI, 0.90-1.84) for 6 to 14 mmHg, and 1.48 (95% CI, 1.03-2.13) for 6 to 21 mmHg without medication and 0.95 (95% CI, 0.55-1.64), 0.95 (95% CI, 0.61-1.48), and 0.95 (95% CI, 0.52-1.75) for the same IOP ranges allowing for medications. Needling rates were 43.0% (early cases group) and 41.5% (later cases group). Complication rates after 1 month occurred in 9.6% (early cases group) and 11.1% (later cases group; P = 0.69). Reoperation rates were 14.8% (early cases group) and 8.1% (later cases group; P = 0.08).

CONCLUSIONS

There is some evidence for improved success in the later cases group. Similar needling rates, similar complication rates, and a slightly higher reoperation rate were found for the early cases group. The results suggest that this procedure can be adopted by existing surgeons with current training regimens, although they may see an improvement in their success outcomes over time.

Animal and cadaver human eyes for residents' surgical training in ophthalmology

In ophthalmology residency programs surgical training plays a vital role in creating confident and skillful surgeons. As almost all ophthalmic surgery needs microscope training, creating a well-taught environment for hand-eye coordination, ocular tissue handling, and anticipation of complications is essential. Wet lab training with animal or cadaver human eyes offers diverse possibilities. We conducted a thorough literature search on various databases to identify the existing literature on wet labs. The results revealed constructive efforts for training novice surgeons in all surgical ophthalmology subspecialties. Wet lab models were initially used only to practice cataract surgery; however, now various complex ocular procedures can be practiced. Ocular surface, corneal, iris, lenticular, scleral, vitreoretinal, extraocular, eyelid, and other adnexal surgeries were reproduced and mastered in many ways. Importantly, with repeated surgical practice, residents gained an increasing level of confidence with enhanced surgical accuracy. In addition, we propose a few novel techniques of various other procedures.

Comparison of Gonioscopy-assisted Transluminal Trabeculotomy Versus Trabeculectomy With Mitomycin C in Patients With Open-angle Glaucoma

PRCIS

Trabeculectomy (TRAB) lowers the intraocular pressure (IOP) more than gonioscopy-assisted transluminal trabeculotomy (GATT) at 18 months, with a reduction in IOP of 30% or more and a significant reduction in the number of glaucoma medications compared with baseline.

PURPOSE

To compare the IOP-lowering efficacy of GATT with mitomycin-C augmented TRAB in patients with uncontrolled open-angle glaucoma.

METHODS

Single-center, retrospective, comparative cohort study. One hundred ten consecutive patients (110 eyes) underwent GATT (n=61) or TRAB (n=49). The primary outcome measure was IOP reduction, defined as a percentage decrease ≥30% and absolute IOP≤18 mm Hg at 18 months with (qualified) or without (complete) medications. Secondary outcomes were visual field change, number of glaucoma medications, complications, and reintervention.

RESULTS

The mean±SD baseline IOP was 30.04±7.5 and 27.59±4.70 (P=0.072) with the mean number of medications of 3.08±0.73 and 2.92±0.91 (P=0.310) in TRAB and GATT, respectively. At 18 months, the mean±SD IOP was 15.26±3.47 mm Hg and 12.48±4.58 mm Hg after GATT and TRAB, respectively (P=0.002). The percentage of IOP lowering from baseline was 56.05±17.72 after TRAB and 42.04±15.56 after GATT (P<0.001). Percentages of complete and qualified success were 59% and 27% after TRAB and 46% and 31% after GATT (P=0.353). No change in visual field loss was observed in both groups. The mean reduction in medications was 2.3±1.4 and 2.1±1.5 in TRAB and GATT, respectively (P=0.493). The most frequent complication after TRAB was hypotony and after GATT hyphema. Reintervention occurred in 8.2% of cases after TRAB and in 14.8% after GATT (P=0.341).

CONCLUSIONS

IOP lowering was greater after TRAB than after GATT at 18 months with a significant reduction in the number of medications after both procedures. Complications and reintervention occurred equally in both groups but differed in type.

Exact matching of trabectome-mediated ab interno trabeculectomy to conventional trabeculectomy with mitomycin C followed for 2 years

PURPOSE

We used exact matching for a highly balanced comparison of ab interno trabeculectomy (AIT) with the trabectome to trabeculectomy with mitomycin C (TRAB).

METHODS

A total of 5485 patients who underwent AIT were exact-matched to 196 TRAB patients by baseline intraocular pressure (IOP), number of glaucoma medications, and glaucoma type. Nearest-neighbor-matching was applied to age. Success was defined as a final IOP of less than 21 mmHg, IOP reduction of at least 20% reduction from baseline, and no secondary surgical interventions. Outcomes were measured at 1, 3, 6, 12, 18, and 24 months.

RESULTS

A total of 165 AIT could be matched to 165 TRAB. The mean baseline IOP was 22.3 ± 5.6 mmHg, and the baseline number of glaucoma medications was 2.7 ± 1.1 in both groups. At 24 months, IOP was reduced to 15.8 ± 5.2 mmHg in AIT and 12.4 ± 4.7 mmHg in TRAB. IOP was lower than baseline at all visits (p < 0.01) and lower in TRAB than AIT (p < 0.01). Glaucoma medications were reduced to 2.1 ± 1.3 in AIT and 0.2 ± 0.8 in TRAB. Compared to baseline, patients used fewer drops postoperatively (p < 0.01) and more infrequently in TRAB than in AIT (p > 0.01). Secondary surgical interventions had the highest impact on success and became necessary in 15 AIT and 59 TRAB patients. Thirty-two challenging events occurred in TRAB and none in AIT.

CONCLUSION

Both AIT and TRAB reduced IOP and medications. This reduction was more significant in TRAB but at the expense of four times as many secondary interventions.

Combining Baerveldt Implant with Trabectome Negates Tube Fenestration: A Coarsened-matched Comparison

Purpose

To assess the efficacy and survival rate of the Trabectome-mediated ab interno trabeculectomy combined with non-fenestrated Baerveldt glaucoma implant compared with the Baerveldt glaucoma implant alone.

Methods

In this retrospective comparative case series, 175 eyes undergoing primary glaucoma surgery (Baerveldt–Trabectome [BT] group: 60 eyes and Baerveldt [B] group: 115 eyes) were included. Participants were identified using the procedural terminology codes. Groups were then matched by Coarsened Exact Matching that resulted in the inclusion of 51 eyes in each group. The primary outcome measure was surgical success defined as 5 mmHg < intraocular pressure (IOP) ≤ 21 mmHg, and IOP reduction ≥ 20% from baseline, and no need to reoperation for glaucoma. Secondary outcome measures were IOP, number of glaucoma medications, and best-corrected visual acuity (BCVA).

Results

The cumulative probability of success at one year was 61% in the BT group and 50% in the B group. IOP decreased from 23.5 ± 2.4 mmHg at baseline to 14.1 ± 2.7 mmHg at the final follow-up in the BT group (P = 0.001). The corresponding values for the B group were 23.2 ± 2.0 mmHg and 13.9 ± 1.6 mmHg, respectively (P = 0.001). There was no significant difference between the groups in terms of IOP at the final follow-up (P = 0.56). The number of medications at baseline was 2.3 ± 0.3 in both groups. However, the BT group needed fewer drops at all postoperative time intervals and used 1.1 ± 0.3 versus 2.0 ± 0.4 eye drops (group B) at the final follow-up visit (P = 0.004). Eyes in B with phacoemulsification had a significantly higher IOP on day 1 compared to B (23.2 ± 14.3 versus 17.9 ± 11.4, P = 0.041). During the one-year follow-up, 7 (13.7%) patients in BT group and 18 (35.2%) in B group experienced hypotony (P = 0.04). No dangerous hypotony or hypertension occurred in BT group. The mean BCVA at baseline was 0.64 ± 0.85 logMAR and changed to 0.55 ± 0.75 logMAR in BT and B groups, respectively (P = 0.663). The corresponding numbers for the final follow-up visit was 0.72 ± 1.07 and 0.63 ± 0.97 logMAR, respectively (P = 0.668).

Conclusion

We observed similar rates of success and IOP reduction using BT and B techniques. BT group needed fewer glaucoma medications. Tube fenestration was unnecessary in BT group resulting in less postoperative ocular hypotony and hypertension. The results of our study indicate that additional trabectome procedure makes Baerveldt glaucoma implant safer, easier to handle, and more predictable in the most vulnerable patients with advanced glaucoma.

A systematic review of simulation-based training tools for technical and non-technical skills in ophthalmology

To evaluate all simulation models for ophthalmology technical and non-technical skills training and the strength of evidence to support their validity and effectiveness. A systematic search was performed using PubMed and Embase for studies published from inception to 01/07/2019. Studies were analysed according to the training modality: virtual reality; wet-lab; dry-lab models; e-learning. The educational impact of studies was evaluated using Messick's validity framework and McGaghie's model of translational outcomes for evaluating effectiveness. One hundred and thirty-one studies were included in this review, with 93 different simulators described. Fifty-three studies were based on virtual reality tools; 47 on wet-lab models; 26 on dry-lab models; 5 on e-learning. Only two studies provided evidence for all five sources of validity assessment. Models with the strongest validity evidence were the Eyesi Surgical, Eyesi Direct Ophthalmoscope and Eye Surgical Skills Assessment Test. Effectiveness ratings for simulator models were mostly limited to level 2 (contained effects) with the exception of the Sophocle vitreoretinal surgery simulator, which was shown at level 3 (downstream effects), and the Eyesi at level 5 (target effects) for cataract surgery. A wide range of models have been described but only the Eyesi has undergone comprehensive investigation. The main weakness is in the poor quality of study design, with a predominance of descriptive reports showing limited validity evidence and few studies investigating the effects of simulation training on patient outcomes. More robust research is needed to enable effective implementation of simulation tools into current training curriculums.

Face and content validity of an artificial eye model for Ab-Interno Goniotomy

PURPOSE

To determine the face and content validity of an artificial eye model for ab-interno goniotomy (SimulEYE KDB model, InsEYEt, Westlake Village, CA) by surveying ophthalmologists with varying experience using a Kahook Dual Blade (KDB; New World Medical, Rancho Cucamonga, CA, USA) following a 90-min wet-lab course using the model.

PARTICIPANTS

Overall 13 ophthalmologists participated following a surgical simulation session on goniotomy using the goniotomy blade at the 2019 Canadian Ophthalmological Society annual meeting.

METHODS

A 17-question survey to assess the face and content validity of the model was given immediately following the surgical simulation session on goniotomy using the goniotomy blade. Responses to each survey question were recorded on a 5-point Likert scale ranging from (1) strongly agree to (5) strongly disagree.

RESULTS

Respondents rated statements regarding the model with a median response of 1 (Strongly Agree) to 3 (Neither agree or disagree). Mann-Whitney U nonparametric analysis revealed no significant difference in responses between instructor vs. non-instructor or between prior experience vs. no prior experience for any of the survey statements. The model received highest survey ratings for utility in training residents, acquisition of surgical skills, accessibility, and higher likelihood of success with the procedure than theory and observation alone. Lowest ratings were for realism of the model compared to a human cadaveric eye.

CONCLUSION

Our results suggest the SimulEYE KDB model is a reasonably cost-effective solution for simulating angle-based surgeries. Additionally, our project shows that experienced ophthalmologists found the artificial eye models useful and helpful for angle-based surgery training.

3D-Reconstruction of the human conventional outflow system by ribbon scanning confocal microscopy

PURPOSE

The risk for glaucoma is driven by the microanatomy and function of the anterior segment. We performed a computation-intense, high-resolution, full-thickness ribbon-scanning confocal microscopy (RSCM) of the outflow tract of two human eyes. We hypothesized this would reveal important species differences when compared to existing data of porcine eyes, an animal that does not spontaneously develop glaucoma.

METHODS

After perfusing two human octogenarian eyes with lectin-fluorophore conjugate and optical clearance with benzyl alcohol benzyl benzoate (BABB), anterior segments were scanned by RSCM and reconstructed in 3D for whole-specimen rendering. Morphometric analyses of the outflow tract were performed for the trabecular meshwork (TM), limbal, and perilimbal outflow structures and compared to existing porcine data.

RESULTS

RSCM provided high-resolution data for IMARIS-based surface reconstruction of outflow tract structures in 3D. Different from porcine eyes with an abundance of highly interconnected, narrow, and short collector channels (CCs), human eyes demonstrated fewer CCs which had a 1.5x greater cross-sectional area (CSA) and 2.6x greater length. Proximal CC openings at the level of Schlemm's canal (SC) had a 1.3x larger CSA than distal openings into the scleral vascular plexus (SVP). CCs were 10.2x smaller in volume than the receiving SVP vessels. Axenfeld loops, projections of the long ciliary nerve, were also visualized.

CONCLUSION

In this high-resolution, volumetric RSCM analysis, human eyes had far fewer outflow tract vessels than porcine eyes. Human CCs spanned several clock-hours and were larger than in porcine eyes. These species differences may point to factors downstream of the TM that increase our vulnerability to glaucoma.

Dose-dependent effects of netarsudil, a Rho-kinase inhibitor, on the distal outflow tract

PURPOSE

To characterize the effects of netarsudil on the aqueous humor outflow tract distal to the trabecular meshwork (TM). We hypothesized that netarsudil increases outflow facility in eyes with and without circumferential ab interno trabeculectomy (AIT) that removes the TM.

METHODS

Sixty-four porcine anterior segment cultures were randomly assigned to groups with (n = 32) and without circumferential AIT (n = 32). Cultures were exposed to 0.1, 1, and 10 μM netarsudil (N = 8 eyes per concentration). For each concentration, IOP and vessel diameters were compared with their respective pretreatment baselines. Outflow tract vessel diameters were assessed by spectral-domain optical coherence tomography (SDOCT) and rendered in 4D (XYZ time series).

RESULTS

Netarsudil at 1 μM reduced IOP both in eyes with TM (- 0.60 ± 0.24 mmHg, p = 0.01) and in eyes without TM (- 1.79 ± 0.42 mmHg, p < 0.01). At this concentration, vessels of the distal outflow tract dilated by 72%. However, at 0.1 μM netarsudil elevated IOP in eyes with TM (1.59 ± 0.36 mmHg, p < 0.001) as well as in eyes without TM (0.23 ± 0.32 mmHg, p < 0.001). Vessels of the distal outflow tract constricted by 31%. Similarly, netarsudil at a concentration of 10 μM elevated IOP both in eyes with TM (1.91 ± 0.193, p < 0.001) and in eyes without TM (3.65 ± 0.86 mmHg, p < 0.001). At this concentration, outflow tract vessels constricted by 27%.

CONCLUSION

In the porcine anterior segment culture, the dose-dependent IOP changes caused by netarsudil matched the diameter changes of distal outflow tract vessels. Hyper- and hypotensive properties of netarsudil persisted after TM removal.

Intraocular pressure reduction in a pigmentary glaucoma model by Goniotome Ab interno trabeculectomy

PURPOSE

To investigate whether microsurgical excision of trabecular meshwork (TM) in an ex vivo pigmentary glaucoma model can normalize the hypertensive phenotype.

METHODS

Eight eyes of a porcine pigmentary glaucoma model underwent 90° of microsurgical TM excision with an aspirating dual-blade (Goniotome (G)). 24 hours later, additional 90° of TM were removed. Anterior segments with sham surgeries served as the control (C). Outflow facility and intraocular pressure (IOP) were analyzed. Histology with hematoxylin and eosin (H&E) was obtained.

RESULTS

After the first 90° TM excision, IOP was significantly lower in G (10.2±2.4 mmHg, n = 7) than C (20.0±2.0mmHg, n = 8, P<0.01). Outflow facility in G (0.38±0.07 μl/min/mmHg) was higher than C (0.16±0.02 μl/min/mmHg, P<0.01). After the second 90° TM excision, IOP in G (6.46±0.81 mmHg, n = 7) was significantly lower than C (20.3±1.7 mmHg, n = 8, P<0.001), while the outflow facility in G (0.50±0.05 μl/min/mmHg, n = 7) was higher than C (0.16±0.01 μl/min/mmHg, n = 8, P<0.001). Compared to the first excision, excision of an additional 90° did not change of IOP (P = 0.20) or outflow facility (P = 0.17) further.

CONCLUSIONS

Excision of 90° of TM in a pigmentary glaucoma model using an aspirating dual-blade decreased IOP and increased outflow facility.

Efficacy and Safety of the Ab-interno Xen Gel Stent After Failed Trabeculectomy

AIMS

To assess the efficacy and safety of the Xen gel stent in reducing intraocular pressure (IOP) in eyes with prior failed trabeculectomy and to determine the frequency of complications and further intervention.

METHODS

Retrospective case note review of all patients with prior trabeculectomy undergoing Xen surgery across 5 centers from August 2015 to May 2017.

RESULTS

In total, 17 surgeries were reviewed. IOP reduced from 21.5 (±2.4) mm Hg preoperatively to 13.6 (±3.4) mm Hg at month 12 (P<0.05). Medication usage reduced from 2.8 (±0.6) preoperatively to 1.0 (±1.3) at month 12 (P<0.05). Adverse events included: numerical hypotony (IOP<6 mm Hg) in 4 cases (23.5%) that all resolved spontaneously, IOP spike of ≥30 mm Hg in 2 (11.8%) cases and transient occlusion of the implant by iris in 1 (5.9%) case. Secondary filtration surgery (Baerveldt tube implantation) was required in 2 (11.8%) cases. Postoperative bleb intervention was required in 9 cases (52.9%), usually in the first month after surgery.

CONCLUSIONS

Xen reduces IOP and number of medications in eyes with failed trabeculectomy. Detailed preoperative conjunctival assessment and targeted stent placement is required. Prospective data and follow-up beyond 12 months are required but Xen seems a viable, effective, and safe option after failed trabeculectomy.

Structure-Function Changes of the Porcine Distal Outflow Tract in Response to Nitric Oxide

Purpose

To correlate outflow function and outflow tract vessel diameter changes induced by nitric oxide (NO).

Methods

In a porcine anterior segment perfusion model, the effects of a nitric oxide donor (100 μM DETA-NO) on outflow facility were compared with controls (n = 8 per group) with trabecular meshwork (TM) and after circumferential ab interno trabeculectomy (AIT). Outflow structures were assessed with spectral-domain optical coherence tomography (SD-OCT) before and after NO, or an NO synthase inhibitor (100 μM L-NAME) and the vasoconstrictor, endothelin-1 (100 pg/mL ET-1). Scans were processed with a custom macroscript and aligned for automated reslicing and quantification of cross-sectional outflow tract areas (CSA).

Results

The facility increased after DETA-NO (Δ of 0.189 ± 0.081 μL/min·mm Hg, P = 0.034) and AIT (Δ of 0.251 ± 0.094 μL/min·mm Hg, P = 0.009), respectively. Even after AIT, DETA-NO increased the facility by 61.5% (Δ of 0.190 ± 0.074 μL/min·mm Hg, P = 0.023) and CSA by 13.9% (P < 0.001). L-NAME + ET-1 decreased CSA by -8.6% (P < 0.001). NO increased the diameter of focal constrictions 5.0 ± 3.8-fold.

Conclusions

NO can dilate vessels of the distal outflow tract and increase outflow facility in a TM-independent fashion. There are short, focally constricting vessel sections that display large diameter changes and may have a substantial impact on outflow.

Outflow facility and extent of angle closure in a porcine model

PURPOSE

To establish the extent of anterior chamber angle circumference needed to maintain a physiological outflow facility (C). This could create a model to investigate focal outflow regulation.

METHODS

Twenty anterior segments of porcine eyes were assigned to five groups, each with a different degree of cyanoacrylate-mediated angle closure: 90° (n = 4), 180° (n = 4), 270° (n = 4), 360° (n = 4), and four unoccluded control eyes. The outflow facility was measured at baseline, 3, 12, 24, and 36 h after angle closure. Outflow patterns were evaluated with canalograms and the histomorphology was compared.

RESULTS

Baseline outflow facilities of the five groups were similar (F = 0.922, p = 0.477). Occlusion of 360° induced a significant decrease in facility from baseline at all time-points (p ≤ 0.023 at 3, 12, 24, and 36 h). However, no difference from baseline was found in any of the partially occluded (0-270°) groups (F ≥ 0.067, p ≥ 0.296 at 3, 12, 24, and 36 h). The canalograms confirmed the extent of occlusion with flow through the unblocked regions. Histology revealed no adverse effects of blockage on the TM or aqueous plexus in the unoccluded angle portions. The unoccluded TM appeared normal.

CONCLUSION

Cyanoacrylate-mediated angle occlusion created a reproducible angle closure model. Ninety degrees of unoccluded anterior chamber angle circumference was sufficient to maintain physiological outflow. This model may help understand how outflow can be regulated in healthy, nonglaucomatous TM.

High-Resolution, Three-Dimensional Reconstruction of the Outflow Tract Demonstrates Segmental Differences in Cleared Eyes

Purpose

The rate of conventional aqueous humor outflow is the highest nasally. We hypothesized that this is reflected in regionally different outflow structures and analyzed the entire limbus by high-resolution, full-thickness ribbon-scanning confocal microscopy (RSCM).

Methods

We perfused pig eyes by anterior chamber cannulation with eight lectin-fluorophore conjugates, followed by optical clearance with benzyl alcohol benzyl benzoate (BABB). RSCM and advanced analysis software (Imaris) were used to reconstruct a three-dimensional (3D), whole-specimen rendering of the perilimbal outflow structures. We performed morphometric analyses of the outflow tract from the level of the trabecular meshwork (TM) to the scleral vascular plexus (SVP).

Results

Except for pigmented structures, BABB cleared the entire eye. Rhodamine-conjugated Glycine max agglutinin (soybean [SBA]) labeled the outflow tract evenly and retained fluorescence for months. RSCM produced terabyte-sized files allowing for in silico dissection of outflow tract vessels at a high resolution and in 3D. Networks of interconnected lumens were traced from the TM to downstream drainage structures. The collector channel (CC) volumes were 10 times smaller than the receiving SVP vessels, the largest of which were in the inferior limbus. Proximal CC diameters were up to four times the size of distal diameters and more elliptical at their proximal ends. The largest CCs were found in the superonasal and inferonasal quadrants where the highest outflow occurs.

Conclusion

RSCM of cleared eyes enabled high-resolution, volumetric analysis of the outflow tract. The proximal structures had greater diameters nasally, whereas the SVP was larger in the inferior limbus.

Is a Day 1 postoperative review following ab interno Xen gel stent surgery for glaucoma needed?

Purpose

To assess whether a first day review is needed following Xen surgery in glaucoma patients.

Patients and methods

We performed a retrospective case note review of all Xen surgeries performed across four centers between August 2015 and May 2017. Intraocular pressure (IOP), number of medications, complications, and all further procedures were recorded.

Results

Two hundred and fifty-nine cases from 226 patients were analyzed, 78 of 259 cases (30.1%) had numerical hypotony (<6 mmHg) on Day 1, but 60 had resolved by Week 1. Zero cases of hypotony required intervention at Day 1. Two of 259 cases (0.8%) had transient IOP of ≥20 mmHg due to air bubble/iris blockage on Day 1 with one case (0.4%) requiring iris manipulation at the slit-lamp. One case (0.4%) required IOP lowering medications at Day 1. All other complications and interventions in our series occurred at 1 week or beyond. Day 1 IOP was not shown to be a reliable indicator for outcomes at Week 1 (r2=0.2155), Month 1 (r2=0.0574), or Month 12 (r2=0.1580).

Conclusion

The presence of significant complications requiring intervention at Day 1 was 0%. Only one case (0.4%) required topical IOP lowering medication and one case (0.4%) needed stent manipulation at Day 1. Day 1 IOP is not a reliable indicator of long-term outcomes in Xen surgeries. Removing Day 1 follow-up would have been safe in our series and it may be more effective to perform the first postoperative review of Xen surgery at Week 1.

Did you choose appropriate tracer for retrograde tracing of retinal ganglion cells? The differences between cholera toxin subunit B and Fluorogold

Cholera toxin subunit B (CTB) and Fluorogold(FG) are two widely utilized retrograde tracers to assess the number and function of retinal ganglion cells (RGCs). However, the relative advantages and disadvantages of these tracers remain unclear, which may lead to their inappropriate application. In this study, we compared these tracers by separately injecting the tracer into the superior Colliculi (SC) in rats, one or 2 weeks later, the rats were sacrificed, and their retinas, brains, and optic nerves were collected. From the first to second week, FG displayed a greater number of labeled RGCs and a larger diffusion area in the SC than CTB; The number of CTB labeled RGCs and the diffusion area of CTB in the SC increased significantly, but there was no distinction between FG; Furthermore, CTB exhibited more labeled RGC neurites and longer neurites than FG, but no difference was evident between the same trace; The optic nerves labeled using CTB were much clearer than those labeled using FG. In conclusion, both CTB and FG can be used for the retrograde labeling of RGCs in rats at 1 or 2 weeks. FG achieves retrograde labeling of a greater number of RGCs than CTB, whereas CTB better delineates the morphology of RGCs. Furthermore, CTB seems more suitable for retrograde labeling of some small, non-image forming nuclei in the brain to which certain RGC subtypes project their axons.

Five-year clinical outcomes of combined phacoemulsification and trabectome surgery at a single glaucoma center

PURPOSE

To analyze the 5-year results of trabectome ab interno trabeculectomy of a single glaucoma center.

METHOD

In this retrospective interventional single-center case series, data of 93 patients undergoing ab interno trabeculotomy between September 2010, and December 2012 were included. Kaplan-Meier analysis was performed using success criteria defined as postoperative intraocular pressure (IOP) ≤ 21 mmHg, and > 20% reduction from preoperative IOP, and no need for further glaucoma surgery. Risk factors for failure were identified using Cox proportional hazards ratio (HR).

RESULTS

The retention rate for 5-year follow-up was 66%. The cumulative probability of success at 1, 2, 3, 4, and 5 years was 82.6%, 76.7%, 73.9%, 72.3%, and 67.5%. Risk factors for failure were lower baseline IOP (HR = 0.27, P = 0.001), younger age (HR = 0.25, P = 0.02), and higher central corneal thickness (HR = 0.18, P = 0.01). Exfoliative glaucoma was associated with a higher success rate (HR = 0.39, P = 0.02). IOP was decreased significantly from 20.0 ± 5.6 mmHg at baseline to 15.6 ± 4.6 mmHg at 5-year follow-up (P = 0.001). The baseline number of glaucoma medications was 1.8 ± 1.2, which decreased to 1.0 ± 1.2 medications at 5 years.

CONCLUSION

Trabectome surgery was associated with a good long-term efficacy and safety profile in this single-center case series with a high retention rate.

Outflow enhancement by three different ab interno trabeculectomy procedures in a porcine anterior segment model

PURPOSE

To evaluate three different microincisional ab interno trabeculectomy procedures in a porcine eye perfusion model.

METHODS

In perfused porcine anterior segments, 90° of trabecular meshwork (TM) was ablated using the Trabectome (T; n = 8), Goniotome (G; n = 8), or Kahook device (K; n = 8). After 24 h, additional 90° of TM was removed. Intraocular pressure (IOP) and outflow facility were measured at 5 and 10 μl/min perfusion to simulate an elevated IOP. Structure and function were assessed with canalograms and histology.

RESULTS

At 5 μl/min infusion rate, T resulted in a greater IOP reduction than G or K from baseline (76.12% decrease versus 48.19% and 47.96%, P = 0.013). IOP reduction between G and K was similar (P = 0.420). Removing another 90° of TM caused an additional IOP reduction only in T and G but not in K. Similarly, T resulted in the largest increase in outflow facility at 5 μl/min compared with G and K (first ablation, 3.41 times increase versus 1.95 and 1.87; second ablation, 4.60 versus 2.50 and 1.74) with similar results at 10 μl/min (first ablation, 3.28 versus 2.29 and 1.90 (P = 0.001); second ablation, 4.10 versus 3.01 and 2.01 (P = 0.001)). Canalograms indicated circumferential flow beyond the ablation endpoints.

CONCLUSIONS

T, G, and K significantly increased the outflow facility. In this model, T had a larger effect than G and K.

A porcine ex vivo model of pigmentary glaucoma

Pigment dispersion can lead to pigmentary glaucoma, a poorly understood condition of younger myopic eyes with fluctuating high intraocular pressure. It has been difficult to investigate its pathogenesis without a model similar to human eyes in size and behavior. Here we present a porcine ex vivo model that recreates several features of pigmentary glaucoma, including intraocular hypertension, accumulation of pigment in the trabecular meshwork, and declining phagocytosis. We found that trabecular meshwork cells regulate outflow, form actin stress fibers, and have a decreased phagocytic activity. Gene expression microarrays and a pathway analysis of TM monolayers as well as ex vivo anterior segment perfusion cultures indicated that RhoA plays a central role in regulating the cytoskeleton, motility, and phagocytosis in the trabecular meshwork, providing new insights and targets to investigate in pigmentary glaucoma.

Intraocular pressure elevation precedes a phagocytosis decline in a model of pigmentary glaucoma

Background: Outflow regulation and phagocytosis are key functions of the trabecular meshwork (TM), but it is not clear how the two are related in secondary open angle glaucomas characterized by an increased particle load. We hypothesized that diminished TM phagocytosis is not the primary cause of early ocular hypertension and recreated pigment dispersion in a porcine ex vivo model.

Methods: Sixteen porcine anterior chamber cultures received a continuous infusion of pigment granules (Pg), while 16 additional anterior chambers served as controls (C). Pressure transducers recorded the intraocular pressure (IOP). The phagocytic capacity of the trabecular meshwork was determined by fluorescent microspheres.

Results: The baseline IOPs in Pg and C were similar ( P=0.82). A significant IOP elevation occurred in Pg at 48, 120, and 180 hours (all P<0.01, compared to baseline). The pigment did not cause a reduction in TM phagocytosis at 48 hours when the earliest IOP elevation occurred, but at 120 hours onward ( P=0.001 compared to C). This reduction did not result in an additional IOP increase at 120 or 180 hours compared to the first IOP elevation at 48 hours ( P>0.05).

Conclusions: In this porcine model of pigmentary glaucoma, an IOP elevation occurs much earlier than when phagocytosis fails, suggesting that two separate mechanisms might be at work.

Predictive value of early postoperative IOP and bleb morphology in Mitomycin-C augmented trabeculectomy

Background: To determine the predictive value of postoperative bleb morphological features and intraocular pressure (IOP) on the success rate of trabeculectomy.

Methods: In this prospective interventional case series, we analyzed for one year 80 consecutive primary open angle glaucoma patients who underwent mitomycin-augmented trabeculectomy. Bleb morphology was scored using the Indiana bleb appearance grading scale (IBAGS). Success was defined as IOP ≤15 mmHg at 12 months. We applied a multivariable regression analysis and determined the area under the receiver operating characteristic curve (AUC).

Results: The mean age of participants was 62±12.3 years in the success and 63.2±16.3 years in the failure group (P= 0.430) with equal gender distribution (P=0.911). IOPs on day 1, 7 and 30 were similar in both (P= 0.193, 0.639, and 0.238, respectively.) The AUC of IOP at day 1, day 7 and 30 for predicting a successful outcome was 0.355, 0.452, and 0.80, respectively. The AUC for bleb morphology parameters of bleb height, extension, and vascularization, on day 14 were 0.368, 0.408, and 0.549, respectively. Values for day 30 were 0.428, 0.563, and 0.654. IOP change from day 1 to day 30 was a good predictor of failure (AUC=0.838, 95% CI: 0.704 to 0.971) with a change of more than 3 mmHg predicting failure with a sensitivity of 82.5% (95% CI: 68 to 91%) and a specificity of 87.5% (95% CI: 53 to 98%).

Conclusions: IOP on day 30 had a fair to good accuracy while bleb features failed to predict success except bleb vascularity that had a poor to fair accuracy.  An IOP increase more than 3 mmHg during the first 30 days was a good predictor of failure.

Predictive value of early postoperative IOP and bleb morphology in Mitomycin-C augmented trabeculectomy

Background: To determine the predictive value of postoperative bleb morphological features and intraocular pressure (IOP) on the success rate of trabeculectomy. Methods: In this prospective interventional case series, we analyzed for one year 80 consecutive primary open angle glaucoma patients who underwent mitomycin-augmented trabeculectomy. Bleb morphology was scored using the Indiana bleb appearance grading scale (IBAGS). Success was defined as IOP ≤15 mmHg at 12 months. We applied a multivariable regression analysis and determined the area under the receiver operating characteristic curve (AUC). Results: The mean age of participants was 62±12.3 years in the success and 63.2±16.3 years in the failure group (P= 0.430) with equal gender distribution (P=0.911). IOPs on day 1, 7 and 30 were similar in both (P= 0.193, 0.639, and 0.238, respectively.) The AUC of IOP at day 1, day 7 and 30 for predicting a successful outcome was 0.355, 0.452, and 0.80, respectively. The AUC for bleb morphology parameters of bleb height, extension, and vascularization, on day 14 were 0.368, 0.408, and 0.549, respectively. Values for day 30 were 0.428, 0.563, and 0.654. IOP change from day 1 to day 30 was a good predictor of failure (AUC=0.838, 95% CI: 0.704 to 0.971) with a change of more than 3 mmHg predicting failure with a sensitivity of 82.5% (95% CI: 68 to 91%) and a specificity of 87.5% (95% CI: 53 to 98%). Conclusions: IOP on day 30 had a fair to good accuracy while bleb features failed to predict success except bleb vascularity that had a poor to fair accuracy.  An IOP increase more than 3 mmHg during the first 30 days was a good predictor of failure.

Freeze-thaw decellularization of the trabecular meshwork in an ex vivo eye perfusion model

Objective

The trabecular meshwork (TM) is the primary substrate of outflow resistance in glaucomatous eyes. Repopulating diseased TM with fresh, functional TM cells might be a viable therapeutic approach. Decellularized TM scaffolds have previously been produced by ablating cells with suicide gene therapy or saponin, which risks incomplete cell removal or dissolution of the extracellular matrix, respectively. We hypothesized that improved trabecular meshwork cell ablation would result from freeze-thaw cycles compared to chemical treatment.

Materials and Methods

We obtained 24 porcine eyes from a local abattoir, dissected and mounted them in an anterior segment perfusion within two hours of sacrifice. Intraocular pressure (IOP) was recorded continuously by a pressure transducer system. After 72 h of IOP stabilization, eight eyes were assigned to freeze-thaw (F) ablation (−80 °C × 2), to 0.02% saponin (S) treatment, or the control group (C), respectively. The TM was transduced with an eGFP expressing feline immunodeficiency viral (FIV) vector and tracked via fluorescent microscopy to confirm ablation. Following treatment, the eyes were perfused with standard tissue culture media for 180 h. TM histology was assessed by hematoxylin and eosin staining. TM viability was evaluated by a calcein AM/propidium iodide (PI) assay. The TM extracellular matrix was stained with Picro Sirius Red. We measured IOP and modeled it with a linear mixed effects model using a B-spline function of time with five degrees of freedom.

Results

F and S experienced a similar IOP reduction of 30% from baseline (P = 0.64). IOP reduction of about 30% occurred in F within 24 h and in S within 48 h. Live visualization of eGFP demonstrated that F conferred a complete ablation of all TM cells and only a partial ablation in S. Histological analysis and Picro Sirius staining confirmed that no TM cells survived in F while the extracellular matrix remained. The viability assay showed very low PI and no calcein staining in F in contrast to many PI-labeled, dead TM cells and calcein-labeled viable TM cells in S.

Conclusion

We developed a rapid TM ablation method that uses cyclic freezing that is free of biological or chemical agents and able to produce a decellularized TM scaffold with preserved TM extracellular matrix in an organotypic perfusion culture.

Angle stability and outflow in dual blade ab interno trabeculectomy with active versus passive chamber management

Purpose

To compare intraoperative angle stability and postoperative outflow of two ab interno trabeculectomy devices that excise the trabecular meshwork with or without active aspiration and irrigation. We hypothesized that anterior segment optical coherence tomography (AS-OCT) allows for a quantitative comparison of intraoperative angle stability in a microincisional glaucoma surgery (MIGS) pig eye training model.

Methods

Twelve freshly enucleated porcine eyes were measured with AS-OCT at baseline, at the beginning of the procedure and at its conclusion to determine the anterior chamber depth (ACD) and the nasal angle α in degrees. The right and left eye of pairs were randomly assigned to an active dual blade goniectome (aDBG) and a passive dual blade goniectome (pDBG) group, respectively. The aDBG had irrigation and aspiration ports while the pDBG required surgery under viscoelastic. We performed the procedures using our MIGS training system with a standard, motorized ophthalmic operating microscope. We estimated outflow by obtaining canalograms with fluorescent spheres.

Results

In aDBG, the nasal angle remained wide open during the procedure at above 90° and did not change towards the end (100±10%, p = 0.9). In contrast, in pDBG, ACD decreased by 51±19% to 21% below baseline (p<0.01) while the angle progressively narrowed by 40±12% (p<0.001). Canalograms showed a similar extent of access to the outflow tract with the aDBG and the pDBG (p = 0.513). The average increase for the aDBG in the superonasal and inferonasal quadrants was between 27 to 31% and for the pDBG between 15 to 18%.

Conclusion

AS-OCT demonstrated that active irrigation and aspiration improved anterior chamber maintenance and ease of handling with the aDBG in this MIGS training model. The immediate postoperative outflow was equally good with both devices.

Training strategies and outcomes of ab interno trabeculectomy with the trabectome

Plasma-mediated ab interno trabeculectomy with the trabectome was first approved by the US Food and Drug Administration in 2004 for use in adult and pediatric glaucomas. Since then, increased clinical experience and updated outcome data have led to its expanded use, including a range of glaucomas and angle presentations, previously deemed to be relatively contraindicated. The main benefits are a high degree of safety, ease, and speed compared to traditional filtering surgery and tube shunts. The increasing burden of glaucoma and expanding life expectancy has resulted in demand for well-trained surgeons. In this article, we discuss the results of trabectome surgery in standard and nonstandard indications. We present training strategies of the surgical technique that include a pig eye model, and visualization exercises that can be performed before and at the conclusion of standard cataract surgery in patients who do not have glaucoma. We detail the mechanism of enhancing the conventional outflow pathway and describe methods of visualization and function testing.