[Clinical, functional and electron microscopy studies on the regenerative ability of the iridocorneal angle region of primate eyes following trabeculotomy]

Historical and Contemporary Debates in Schlemm's Canal-Based MIGS

Glaucoma is one of the primary causes of blindness worldwide. Canal opening surgery, a type of minimally invasive glaucoma surgery (MIGS) applied in cases of mild to moderate glaucoma, has gained increasing popularity in recent years due to its efficacy in reducing the intraocular pressure, its safety profile, the simplicity of its technique, and the reduced likelihood of compromised vision. Nevertheless, the existing body of histopathological studies remains insufficient for a comprehensive understanding of post-surgical wound healing. Consequently, debates persist among researchers regarding the mechanism through which Schlemm's canal opening surgery reduces the intraocular pressure, as well as the surgical techniques that may impact the outcomes and the factors influencing surgical success. As the history of MIGS is relatively short and lacks sufficient systemic reviews or meta-analyses evaluating the influence of individual factors, this review was conducted to illuminate the disparities in researchers' opinions at the current stage of research.

Consequences of Clot Formation and Hyphema Post-Internal Trabeculotomy for Glaucoma

PRCIS

Clot formation and hyphema following internal trabeculotomy represent distinct clinical entities. The eyes with clot formation exhibited a more pronounced postsurgical intraocular pressure spike, longer residual intracameral bleeding, and a higher risk of reoperation.

PURPOSE

The aim of this study was to investigate the consequences of clot formation and hyphema in the anterior chamber after internal trabeculotomy.

MATERIALS AND METHODS

In this retrospective interventional comparative study, we investigated the surgical outcomes of internal trabeculotomy in 142 eyes of 142 patients at Sensho-kai Eye Institute.

RESULTS

Concurrent clot formation and L≥2 hyphema (height of hyphema ≥1 mm) was observed in 22 eyes. In these cases, the postsurgical IOP was 29.3 mm Hg at 1 week, significantly higher than the 16.1 mm Hg in eyes that had L≥2 hyphema but without clot formation ( P =0.0002). However, the 1-week postsurgical IOP in L≥2 hyphema and clot (-) eyes, which measured 16.1 mm Hg was not significantly greater than that in L<2 hyphema and clot (-) eyes, which measured 18.7 mm Hg ( P =0.162). Thus, clot formation was identified as a significant factor contributing to high postsurgical IOP at 1 week. The resolution time for anterior chamber bleeding in eyes with concurrent clot formation and L≥2 hyphema was 12.3 days, longer than the 5.8 days observed in L≥2 hyphema eyes without clot formation ( P =0.016). Among the 22 eyes with concurrent L≥2 hyphema and clot formation, 8 required anterior chamber washout. Three of the 10 eyes that underwent washout necessitated additional trabeculectomy, a rate significantly higher than that in nonwashout eyes ( P <0.001).

CONCLUSIONS

After internal trabeculotomy, the sequelae of concurrent clot formation and L≥2 hyphema in the anterior chamber were more severe than those of simple hyphema without clots. Clot formation negatively affected postoperative IOP.

Randomised clinical trial for morphological changes of trabecular meshwork between Kahook dual-blade goniotomy and ab interno trabeculotomy with a microhook

We demonstrated whether the difference of trabecular meshwork remodeling occur depending on the incisional cross-sectional area by comparing Kahook dual-blade goniotomy (KDB) and ab interno trabeculotomy with a microhook. Phakic eyes with primary open-angle or exfoliative glaucoma were randomised into a KDB or a microhook group. The primary outcome was an incisional cross-sectional area quantified by anterior segment optical coherence tomography. In subgroup analysis, the number of patients with the unidentifiable incisional area was compared between the groups. Secondary outcomes were the rate of intraocular pressure changes, the laser flare metre values, corneal endothelial cell densities, the number of glaucoma medications, the usage rate per glaucoma medication type and postoperative complications between the two groups. A total of 29 eyes in 29 patients in the KDB and microhook group were included respectively, with an overall mean age of 72.6 ± 8.1 years. The incisional cross-sectional area of the KDB group was significantly larger at 1 week and at 1, 6 and 12 months (p < 0.01) postoperatively. The number of patients with the nonidentified incisional area was higher at 1, 6 and 12 months postoperatively (p ≤ 0.03) in the microhook group. The flare values in the KDB group were higher than those in the microhook group at 12 months postoperatively (p = 0.02). No significant differences were observed in other secondary outcomes. Incisional cross-sectional area remains larger in eyes treated with KDB goniotomy than in those treated with ab interno trabeculotomy with the microhook, whereas KDB goniotomy did not have an advantage in controlling intraocular pressure postoperatively.Trial registration: UMIN000041290 (UMIN, University Hospital Medical Information Network Clinical Trials Registry of Japan; date of access and registration, 03/08/2020).

Outcomes of Penetrating Canaloplasty in Childhood Glaucoma

PRCIS

Penetrating canaloplasty was safe and effective for the management of refractory childhood glaucoma.

PURPOSE

The purpose of this paper is to report the safety and efficacy of penetrating canaloplasty for the management of childhood glaucoma.

MATERIALS AND METHODS

This single-center prospective interventional case series enrolled 50 eyes of 32 patients with childhood glaucoma between July 2017 and July 2020. Penetrating canaloplasty to create direct communication between the anterior chamber and tensioning suture-dilated the Schlemm canal was performed through a trabecular meshwork ostium in the affected eyes. Preoperative and postoperative intraocular pressure (IOP), number of glaucoma medications, and procedure-related complications were recorded. Qualified and complete success was defined as IOP≥5 and ≤21 mm Hg with or without glaucoma medications, respectively.

RESULTS

A total of 43 eyes (86.0%) achieved 360 degrees catheterization of Schlemm canal and completed penetrating canaloplasty. The median age at surgery was 5 years (range, 10 d-17 y, mean 6.20±5.46 y). The mean IOP decreased from 33.11±10.89 mm Hg on 2 medications (median, range: 0-5) before surgery to 13.46±4.71 mm Hg on 0 medications (median, range:0-2) postoperatively at 12 months ( P <0.001). Complete and qualified success rates were 81.08% and 89.19%, respectively, at the 12-month follow-up. Hyphema (6/43, 13.95%) and a transient shallow anterior chamber with hypotony (5/43, 11.63%) were the most commonly observed early complications.

CONCLUSION

Penetrating canaloplasty demonstrated good safety and efficacy in eyes with childhood glaucoma, and may be considered an option for managing refractory childhood glaucoma.

Histological analysis of trabeculotomy - An investigation on the intraocular pressure lowering mechanism

The primary aim of trabeculotomy (TLO) and/or minimally invasive glaucoma surgery (MIGS) is to produce a direct communication between the anterior chamber (AC) and collector channels (CC), which is believed to be the process by which intraocular pressure (IOP) is normalized. However, we previously reported our finding of the large opening of the Schlemm's canal (SC) into the AC in eyes with failed TLO (Amari et al., 2015). If the routes from the AC to the CC by TLO/MIGS are direct, IOP should be stabilized at around aqueous vein pressure if the SC and CC are undamaged. However, in eyes in which TLO/MIGS is successful, IOP usually stays at around the middle or high teens post surgery. In this current study, we retrospectively investigated the specific reason for middle- or high-teens IOP following TLO/MIGS via the histological examination of trabeculectomy (TRAB) specimens that include the area of previous TLO/MIGS in eyes with failed TLO or insufficient IOP control following TLO by specifically focusing on the behavior of the SC endothelium (SCE). Patient background, maximum IOP prior to TLO/MIGS and TRAB, the number medications administered, and elapsed time between TLO/MIGS and TRAB were reviewed. In 42 TRAB specimens of 31 120-180° TLO eyes (Group A; 27 ab-externo and 4 ab-interno eyes) and 11 360° suture TLO eyes (Group B), SC length (SCL), the site of the incision in the trabecular meshwork (TM) [i.e., the center (CEN)/anterior-tip (TIP)], and TM opening into the AC [i.e., open (OPN)/closed (CLS)] were histologically investigated. The correlation between the clinical parameters of the maximum IOP of pre-TLO/MIGS, the maximum IOP of pre-TRAB, the percentage of IOP reduction (PIR), and the histological results were statistically evaluated. Our findings revealed a significant negative correlation between the maximum IOP of pre-TRAB and SCL (P = 0.0167), and a significantly higher PIR in the eyes with OPN than those with CLS in Group A (P = 0.0045). However, no significant difference in SCL was found between the OPN and CLS eyes in both groups. In comparison to Group A, a higher percentage of OPN (82%) yet a smaller SCL (P = 0.0024) was observed in Group B. No significant correlation between clinical and histological parameters was found in Group B. In both groups, the common finding was sealing of the SC openings by SC endothelium (SCE) and no direct communication between the AC and the CC. This fact indicates that the nature by which SCE seals off the opened SC lumen into the AC created by TLO may be very important for maintaining the blood-aqueous barrier. Based on these results, we concluded that accessibility for aqueous humor to the SC and preservation of the SC may be important for lowering IOP by TLO. However, the opening of the SC into the AC (OPN type) does not guarantee an adequate IOP lowering effect if the SC is widely collapsed. Thus, TLO may be improved only by eliminating the most resistant part of the TM with minimal SCE damage.

Effects of Preoperative Intraocular Pressure Level on Surgical Results of Microhook Ab Interno Trabeculotomy

To assess the roles of preoperative intraocular pressure (IOP) level on the IOP reducing efficacy of microhook ab interno trabeculotomy (µLOT), 126 consecutive open-angle glaucomatous eyes (90 primary open angle glaucoma, 36 exfoliation glaucoma) of 126 Japanese subjects (60 men, 66 women; mean age ± standard deviation, 70.5 ± 11.4 years) who underwent µLOT alone (25 eyes, 20%) or combined µLOT and cataract surgery (101 eyes, 80%) were retrospectively included, and subdivided into four groups based on the quartile of preoperative IOP: Q1, ≤15 mmHg; Q2, 15–18 mmHg, Q3, 18–21 mmHg, and Q4, >21 mmHg. Preoperative and 12 months postoperative IOPs and numbers of antiglaucoma medications were compared among IOP groups. Factors associated with postoperative IOP were assessed using multivariate analysis, and the success of IOP control was assessed with various definitions. Postoperatively, IOP was significantly higher in Q3 (p < 0.0146) and Q4 (p = 0.0320) groups than Q1 group, while the number of medications was not significantly different among four IOP groups (p = 0.1966). Older age was associated with lower postoperative IOP, and higher preoperative IOP was associated with higher postoperative IOP, while sex, glaucoma type, surgical procedure, lens status, extent of trabeculotomy incision, and preoperative number of medications were not associated with postoperative IOP. The success rates for IOP ≤ 18 and ≤15 mmHg were higher in lower preoperative IOP groups (i.e., Q1 and Q2) than higher preoperative IOP groups (Q3 and Q4), while the success rate for ≥20% IOP reduction was higher in higher preoperative IOP groups than in lower preoperative IOP groups; the success rate for ≥0% IOP reduction was equivalent among groups. By reviewing the previous studies in ab interno trabeculotomy/goniotomy procedures, positive correlation between preoperative and postoperative IOPs was preserved throughout the studies and surgical procedures. After the µLOT, larger %IOP reduction was achieved in higher preoperative IOP groups than in lower preoperative IOP groups, while postoperative IOP was still lower than in lower preoperative IOP groups.

Turn Back Elevation of Once Reduced IOP After Trabeculotomy Ab Externo and Kahook Dual Blade Surgeries Combined with Cataract Surgery

Purpose

To evaluate the surgical outcome of internal trabeculectomy by Kahook dual blade (KDB) with that of external trabeculotomy, each combined with phaco-lensectomy and intraocular lens implantation (Phaco).

Patients and Methods

This is a retrospective comparative study. The primary and secondary outcome measures are postsurgical intraocular pressure and postsurgical hyphema. One eye each of 76 primary open angle glaucoma (POAG), pseudoexfoliation glaucoma (PEG) and ocular hypertension (OH) patients underwent external phaco-trabeculotomy, and that of 40 POAG, PEG and OH patients underwent phaco-KDB surgery.

Results

Reduction of the intraocular pressure (IOP) by phaco-KDB at one and two years was 28.4 and 27.8%, respectively, and was not significantly different from that by external phaco-trabeculotomy of 32.7% (P=0.256) and 31.5% (P=0.468), respectively. Three months postsurgical IOP after phaco-KDB and external phaco-trabeculotomy was 16.1 and 15.9 mmHg, respectively. There was a significant turn back elevation of once reduced IOP to 17.1 (P=0.0207) and 17.0 mmHg (P=0.0096) at 24 months, respectively. There were no differences in success probability to achieve IOP below 17 mmHg (P=0.120), 21 mmHg (P=0.719) and >20% IOP reduction (P=0.309) with medication(s) at two years between the phaco-KDB and external phaco-trabeculotomy cohorts. Younger age was a significant (P<0.001) risk factor for failure; however, presurgical IOP (P=0.466), the type of surgery (P=0.219) and presence of postsurgical IOP spike (P=0.737) were not significant risk factors by the Cox proportional hazard model. Hyphema and spike of the IOP in phaco-KDB and external phaco-trabeculotomy cohorts were 40% and 88% (P<0.001), and 53% and 41% (P=0.238), respectively.

Conclusion

The IOP reduction by the phaco-KDB was equivalent to that by external phaco-trabeculotomy up to two years. In both cohorts, once reduced postsurgical IOP tend to increase up to 24 months.

Modified deep sclerectomy (D-lectomy MMC) for primary open-angle glaucoma: preliminary results

PURPOSE

To evaluate the outcome of modified deep sclerectomy [D-lectomy mitomycin C (MMC)] for medically refractory glaucoma patients.

METHODS

In a retrospective comparative study, the surgical outcome in 1 eye each of 31 patients who underwent D-lectomy MMC was compared with that of 91 eyes of 91 patients who underwent trabeculectomy with adjunctive MMC. These eyes had a diagnosis of primary open-angle glaucoma or pseudoexfoliation glaucoma, a record of high intraocular pressure (IOP) exceeding 25 mm Hg, and planned for surgical intervention. In the D-lectomy MMC cases, a slit incision at the trabecular meshwork and peripheral iridectomy were created. The "lake" and trabeculo-Descemet membrane ("window") were examined by ultrasound biomicroscope, gonioscopy, and time-domain optical coherence tomography.

RESULTS

Postsurgical IOP at 1, 3, 6, and 12 months after the D-lectomy MMC and trabeculectomy MMC were comparable (P=0.63-0.97). The filtering bleb was noted in 14 (45%) of the 31 D-lectomy MMC eyes at 3 months, and their survival was significantly less than trabeculectomy MMC subjects in which 81 of 91 eyes had the bleb at 3 months (P<0.0001). The lake was noted in 29 of 31 D-lectomy MMC eyes. The sealing of the once penetrated trabecular meshwork was complete at 3 months in 23 of 29 eyes by ultrasound biomicroscopic and/or gonioscopic examinations, whereas that was incomplete in 6 eyes.

CONCLUSIONS

Addition of a slit incision to the trabecular meshwork and peripheral iridectomy (D-lectomy MMC) improved postsurgical IOP of the deep sclerectomy to the level comparable with trabeculectomy MMC, with a less frequency of the bleb formation.

Factors leading to reduced intraocular pressure after combined trabeculotomy and cataract surgery

PURPOSE

To determine the factors that control intraocular pressure (IOP) after trabeculotomy combined with phacoemulsification and intraocular lens implantation as an initial procedure in adults with primary open-angle glaucoma (POAG).

METHODS

A consecutive series of 141 eyes with POAG or ocular hypertension was prospectively recruited. One hundred five eyes were treated by combined trabeculotomy and cataract surgery (TPI group) and 36 eyes were treated by cataract surgery alone (PI group). The prognostic factors that correlate with successful IOP control after surgery were screened using the Cox multivariate analyses based on three definitions of success: IOP <21 mm Hg, <17 mm Hg, and <15 mm Hg, with or without eye drops. The factors examined were types of procedure (TPI or PI), age, sex, preoperative IOP level, number of preoperative antiglaucoma medications, eyes with high myopia (>-10 diopters), postoperative hyphema lasting longer than 4 days, and postoperative transient IOP spike (>30 mm Hg).

RESULTS

TPI was a significant factor for IOP reduction in the three definition-based multivariate analyses. Other factors included patient age, preoperative IOP level, and postoperative IOP spike. The statistical significance of age was further confirmed using linear regression analysis and the Spearman correlation coefficient (Rs) between age and IOP level 3 months after surgery (R(2)=0.13, P = 0.0002 and Rs=-0.44, P < 0.0001, respectively in the TPI group). The success rates for IOP control <17 mm Hg and <15 mm Hg were significantly higher in patients 70 years and older than in younger patients, as determined using the Kaplan-Meier life table analysis with the Mantel-Cox logrank test in both TPI and PI groups. IOP reduction was significantly greater in older patients than in younger patients at every follow-up visit for up to 1.5 years for the TPI group and up to 1 year for the PI group.

CONCLUSION

Advanced age is a favorable prognostic factor for successful control of IOP after combined trabeculotomy and cataract surgery. Older patients with POAG and visually significant cataract are good candidates for combined trabeculotomy and cataract surgery.

Perspectives in trabecular surgery

The aim of trabecular surgery is to selectively combat the diseased structure central to the pathogenesis of chronic open-angle glaucoma, thereby reducing potential hazards during and after conventional filtering procedures. This overview considers new techniques in ab interno trabecular surgery. Special emphasis is placed on the description of each novel technique, its instrumentation, presumed mechanism of action and clinical results. Trabecular aspiration is evaluated as a method of clearing intertrabecular spaces of extracellular debris in pseudoexfoliation glaucoma with or without simultaneous cataract surgery or goniocurettage, while laser trabecular ablation is discussed for the treatment of absolute glaucomas. Where corneal haze has formed visualisation of the anterior chamber angle structures and trabecular surgery is performed with the aid of a microendoscope. Although the results are very promising it should be understood that some of these procedures are still in the experimental phase and are undergoing careful clinical evaluation, leaving plenty of room for refinements and further developments.

Goniocurettage for removing trabecular meshwork: clinical results of a new surgical technique in advanced chronic open-angle glaucoma

PURPOSE

To elucidate the long-term outcome of goniocurettage as a new technique in trabecular microsurgery for advanced open-angle glaucoma.

METHODS

In a prospective, nonrandomized clinical trial, 25 eyes of 25 patients with a mean age +/- SD of 72.7+/-10.1 years (range, 50 to 89 years) with uncontrolled chronic open-angle glaucoma that had undergone failed filtering procedures were treated by goniocurettage. Trabecular tissue was scraped away from the chamber angle by means of an instrument similar to a microchalazion curette (diameter, 300 microm).

RESULTS

Before surgery, intraocular pressure ranged from 29 to 48 mm Hg (mean +/- SD, 34.7+/-7.1 mm Hg), and mean number of antiglaucoma medications was 2.2+/-0.56. Follow-up averaged (+/-SD) 32.6+/-8.1 months (range, 30 to 45 months). Overall success, defined as postoperative intraocular pressure of 19 mm Hg or less with one pressure-reducing agent, was attained in 15 eyes (60%), with five eyes (20%) being controlled without medication. Considering all successfully treated patients, the mean intraocular pressure was 17.7+/-3.1 mm Hg (range, 10 to 19 mm Hg) at the final visit. Mean intraocular pressure reduction was 17.1+/-7.1 mm Hg in these eyes, representing a net decrease from baseline of 49%. Number of antiglaucoma medications dropped to 0.63+/-0.29. Complications included localized Descemet membrane detachment in five eyes (20%) and moderate anterior chamber bleeding in four eyes (16%).

CONCLUSIONS

This new surgical technique can effectively control intraocular pressure for long periods of time in patients with open-angle glaucoma and a history of failed filtering procedures. Goniocurettage may be a suitable alternative to surgical treatment of glaucoma patients with excessive conjunctival scarification.

Intraocular pressure response to combined phacoemulsification and trabeculotomy ab externo versus phacoemulsification alone in primary open-angle glaucoma

We investigated trabeculotomy ab externo as a means of optimizing intraocular pressure (IOP) control in glaucoma patients having phacoemulsification and implantation of an intraocular lens (IOL). A prospective, randomized, controlled study was performed to evaluate the effect on IOP and the incidence of complications associated with combined phacoemulsification and trabeculotomy ab externo. The study group had the combined procedure, while the control group had only phacoemulsification with IOL implantation. A total of 106 patients were randomized, and the IOP for each group was compared at 3, 6, 12, and 24 months. At two years, the mean IOP reduction was 6.1 mm Hg in the study group and 3.8 mm Hg in the control group (P = .001). There were no complications in the control group. Two complications (2/53 or 3.8%) occurred in the study group: a small tear in Descemet's membrane and a postoperative microhyphema. There was no increase in medication in either the study or control group. Combined phacoemulsification and trabeculotomy ab externo represents an option to lower IOP and potentially reduce the need for pressure-lowering medications in patients with primary open-angle glaucoma and visually significant cataracts.

Ultrastructural changes of the trabecular meshwork of the monkey (Macaca speciosa) following irradiation with argon laser light

An attempt to elucidate the mechanism of the pressure-lowering effect after treatment of the chamber angle according to Wise and Witter with argon laser light is presented. The ultrastructural effects upon the trabecular meshwork of four Macaca speciosa monkeys were analyzed at planned intervals by scanning and transmission electron microscopy. The ultrastructural effects of the treatment are strongly dependent on the site of the laser burns. Whereas burns delivered to the anterior part of the meshwork are tightly sealed by a monocellular layer of atypical corneoendothelial cells, this mechanism is less marked when delivered more posteriorly.

Trabeculo-electropuncture in cynomolgus monkeys (Macaca irus)

Trabeculo-electropuncture (TEP) was performed in one eye of ten cynomolgus monkeys. In five control eyes, the TEP probe was inserted into Schlemm's canal and withdrawn without causing a spark discharge. In another five control eyes,a scleral window was produced and the canal was opened, but no probe was inserted. The gross facility of outflow was determined prior to the operation and 2, 6, and 18 weeks postoperatively. TEP had no longlasting effect on the facility. Gonioscopy five months after the operation revealed marked changes in the anatomy of Schlemm's canal in treated eyes and in control eyes subjected to probe insertion. Control eyes without probe insertion appeared normal. Six months postoperatively three monkeys were killed and the eyes investigated. Light and electron microscopy indicated that insertion of the probe with or without spark discharge resulted in the formation of dense bridges between the inner and outer walls of Schlemm's canal. At the sites of TEP, the trabecular meshwork was replaced by dense scar tissue containing irregular, fine fibrillar material, elastic fibres and large amounts of curly collagen. There were no intertrabecular spaces in the scar tissue. In one eye, one lesion was covered by a thin endothelium resting on a basal membrane. The results indicate that the failure of TEP in monkey eyes was due to the formation of dense scar tissue occluding the openings initially produced by the spark discharge.