In vivo analysis of conjunctiva in canaloplasty for glaucoma

Safety and Efficacy of Three Modifications of Canaloplasty to Treat Open-Angle Glaucoma: 3-Year Outcomes

BACKGROUND

This is a report of 3-year results of a prospective assessment of three modifications of canaloplasty (C): ab externo (ABeC), mini-canaloplasty (miniABeC), and ab interno (ABiC) performed concomitantly with cataract removal in subjects suffering from primary open-angle glaucoma (POAG).

METHODS

Forty-eight individuals were randomized for one of the surgeries: ABeC, miniABeC, or ABiC and cataract removal-16 eyes for each group. Follow-up examinations were carried out on the day of the surgery, on days 1 and 7, after 1, 3, 6 months, and at 1, 2, and 3 years. Complete and qualified success was an IOP ≤ 15 mmHg without or with antiglaucoma eye drops, respectively. The IOP reduction of 20% or more was considered an additional success criterion.

RESULTS

Within three years the probability of qualified success was ABiC and miniABeC-94%, ABeC-100%, and of complete success ABiC-75%, miniABeC-100%. At the 3-year follow-up, the median IOP decreased from 22 to 15 mmHg in the ABeC group (p = 0.001), from 22 to 15 mmHg in the miniABeC group 15 (p < 0.001), and from 21 to 15 mmHg in the ABiC group (p = 0.001) compared to the post-washout stage. The IOP dropped by 20% or more without medications in 56.2% of patients post ABiC, 68.8% post miniABeC and 75% post ABeC. The median number of antiglaucoma medications dropped in all three groups; at the 3-year follow-up, only one patient following ABeC and four subjects following miniABeC required treatment. One patient required reoperation and further intensification of topical treatment-post miniABeC. The levels of IOP, CDVA, and success probability at the 36-month follow-up showed no significant difference for individual groups.

CONCLUSIONS

ABeC, miniABeC, and ABiC have significant IOP-lowering potential in individuals diagnosed with POAG at a mild to moderate stage and no history of IOP ≥ 30 mmHg with a good safety profile.

Safety and Efficacy of Three Variants of Canaloplasty with Phacoemulsification to Treat Open-Angle Glaucoma and Cataract: 12-Month Follow-Up

Background: A single-center prospective randomized observational study to compare three types of canaloplasty, i.e., ab externo (ABeC), minicanaloplasty (miniABeC) and ab interno, (ABiC) combined with cataract surgery in primary open-angle glaucoma (POAG) patients over 12 months. Methods: 48 POAG patients underwent one of three canaloplasty procedures: ABeC (16 eyes), miniABeC (16 eyes) or ABiC (16 eyes) or combined with phacoemulsification. Patients were assessed at baseline, at day 0–1–7 and at month 1–3–6–12. Successful treatment was defined as unmedicated IOP reduction ≥20%. Complete surgical success was defined as an IOP ≤ 15 mmHg without medications, and a qualified surgical success as IOP ≤ 15 mmHg with or without medications. Results: Pre-washout IOP median values (mmHg) were 17 (ABeC), 18 (miniABeC) and 17 (AbiC) and decreased at 12-month follow up postoperatively to 13 (p = 0.005), 13 (p = 0.004) and 14 (p = 0.008), respectively—successful treatment was achieved in approximately 100% of patients for ABeC and in 93.8% for both miniABeC and AbiC groups. Preoperatively, the median number of medications was 2.0 (range 1–3) (ABeC), 2.0 (1–3) (miniABeC) and 2.0 (0–4) (ABiC); 12-month post-operatively, all medications were withdrawn except in two patients (followed miniABeC and AbiC). Conclusions: The three variants of canaloplasty significantly reduced IOP and the number of medications in patients with mild to moderate POAG and gave no significant complications.

Size Matters: Ab Interno Canaloplasty Revision with Suture Trabeculotomy

Aim

To report the efficacy of the revision of failed ab interno canaloplasty with micro-invasive suture trabeculotomy (MIST) over a follow-up period of 24 months.

Materials and methods

A retrospective analysis was performed on 23 eyes with open-angle glaucoma (OAG), on whom an ab interno canaloplasty revision with MIST was performed for glaucoma progression. The primary outcome was the proportion of eyes with a significant intraocular pressure (IOP) reduction at 12 months post trabeculotomy, defined as an IOP ≤ 18 mm Hg or ≥20% reduction in IOP without any secondary intervention (SI), and with the same or fewer number of glaucoma medications (NGM). All parameters, including best corrected visual acuity (BCVA), IOP, NGM, and SI, were evaluated at 1, 6, 12, 18, and 24 months.

Results

At 12 months, eight out of 23 eyes (36.4%) achieved complete success, maintained in six eyes (27.3%) at 24 months. A significantly lower mean IOP was recorded at all visits [14.3 ± 4.0 mm Hg at 24 months vs 23.1 ± 6.8 mm Hg at baseline (BL)] with a percent IOP change of up to 27.3% at 24 months postoperatively. NGM and BCVA did not significantly decrease from BL. A total of 11 eyes (47.8%) needed an SI throughout the follow-up period.

Conclusion

Ab interno trabeculotomy in patients with failed canaloplasty was not shown to be effective in providing a satisfactory control of IOP in OAG patients, possibly due to the small suture gauge used in the initial canaloplasty.

Clinical significance

Further research is needed to optimize the surgical outcome.

How to cite this article

Seif R, Jalbout NDE, Sadaka A, et al. Size Matters: Ab Interno Canaloplasty Revision with Suture Trabeculotomy. J Curr Glaucoma Pract 2022;16(3):152-157.

Updates on the utility of anterior segment optical coherence tomography in the assessment of filtration blebs after glaucoma surgery

The formation of filtration blebs is the main drainage mechanism for reducing intraocular pressure after traditional incisional glaucoma surgery such as trabeculectomy and non-penetrating deep sclerotomy. Early and short-lasting blebs may also occur after canaloplasty. Bleb formation also plays an important role after the implantation of glaucoma drainage devices, including Minimally Invasive Glaucoma Surgery devices. Anterior segment optical coherence tomography (AS-OCT) is a rapid and non-invasive high-resolution imaging technique that has evolved in recent years to become a routine examination. Anterior segment optical coherence tomography (AS-OCT) provides key information in the assessment and follow-up of glaucoma surgery, especially in the assessment of filtration blebs. Thus, bleb morphology can be qualitatively classified into diffuse, cystic, encapsulated and flattened, and AS-OCT imaging can also provide several quantitative parameters of the bleb, such as total bleb height, bleb fluid-filled cavity height, bleb wall thickness, number of microcysts and trabeculectomy opening size. These parameters could have an impact on clinical management during follow-up because they may predict the success or failure of the surgery in the early and late postoperative periods. Additionally, they may also guide the procedures used to increase filtration and reduce intraocular pressure, such as bleb needling and laser suture lysis.

Aerobic exercise reduces intraocular pressure and expands Schlemm's canal dimensions in healthy and primary open-angle glaucoma eyes

Purpose

Aerobic exercise (AE) has been reported to decrease intraocular pressure (IOP) in healthy subjects and there are concomitant morphological changes in the anterior segment of the eye including the Schlemm's canal (SC). However, its effects on IOP and SC morphology in glaucoma patients had not been studied before. We aim to investigate the effect of AE on the IOP and SC dimension in both healthy and primary open-angle glaucoma (POAG) eyes.

Methods

The area and diameter of SC and IOP were measured in 35 primary open-angle glaucoma (POAG) patients (59 eyes) and 36 healthy subjects (72 eyes) before and after performing moderate intensity of AE by running on a treadmill for 30 min. SC was imaged by swept-source optical coherence tomography (SS-OCT) for evaluation.

Results

In comparison with baseline values, mean IOP decreased significantly following AE in both POAG and healthy eyes (both P < 0.001), in which POAG eyes showed a greater degree of reduction compared to healthy eyes (P = 0.002). In comparison with baseline values, in both POAG and healthy eyes, the average cross-sectional area (POAG: 80.48 +/- 59.54 vs. 99.20 +/- 54.87 pixels; healthy: 151.84 +/- 52.76 vs. 198.23 +/- 53.70 pixels; both P < 0.001) and diameter (POAG: 3.73 +/- 1.69 vs. 4.33 +/- 1.74 pixels; healthy: 5.61 +/- 1.02 vs. 6.47 +/- 1.20 pixels; both P < 0.001) of SC significantly increased after AE. In POAG, both treated and untreated with IOP-lowering medications, a significant reduction in mean IOP and increase in SC dimensions following AE were observed (all P < 0.05), and there were no significant differences of such measurements between the two subgroups (all P > 0.05).

Conclusion

AE-induced reduction in IOP and an increase in SC dimensions in POAG eyes as in healthy eyes. Further studies to evaluate the long-term effect of AE on IOP control and SC morphology in POAG seem warranted.

Comparison of Ab Externo and Ab Interno 360-degree Suture Trabeculotomy in Adult Open-angle Glaucoma

PRECIS

Ab interno (gonioscopy-assisted transluminal trabeculotomy) and ab externo 360-degree suture trabeculotomy (ST) achieved similar success rates for reducing intraocular pressure (IOP) without serious complications threatening visual acuity.

PURPOSE

We aimed to compare the efficacy of ab externo and ab interno 360-degree ST in reducing IOP, decreasing the number of antiglaucoma medications required, and decreasing the rates of intraoperative/postoperative complications in adults with open-angle glaucoma (OAG).

PATIENTS AND METHODS

This retrospective study included 33 eyes of 33 patients who underwent ab externo 360-degree ST (group 1) and 23 eyes of 23 patients who underwent ab interno 360-degree ST for OAG (group 2). We analyzed demographics as well as preoperative and postoperative (1, 3, 6, and 12 mo) data related to IOP, the number of antiglaucoma medications, complications, and surgical success rates.

RESULTS

In group 1, the mean IOP was 26.2±10.4 mm Hg, and the mean number of antiglaucoma medications was 3.2±1.0 preoperatively, decreasing to 11.2±3.0 mm Hg and 0.1±0.4 at 12 months, respectively (P<0.001, <0.001). In group 2, the mean IOP was 28.3±10.4 mm Hg, and the mean number of antiglaucoma medications was 3.5±0.9 preoperatively, decreasing to 13.3±6.5 mm Hg and 0.8±1.0 at 12 months, respectively (P<0.001, <0.001). Decreases in IOP at 6 and 12 months were similar in groups 1 and 2 (50% vs. 47%, P=0.6; and 51% vs. 49%, P=0.7, respectively). At 12 months, complete and qualified success rates were 88% and 97% for group 1 and 57% and 87% for group 2, respectively. The most common complications in both groups were hyphema and transient IOP spikes.

CONCLUSION

Ab interno 360-degree ST is similar to ab externo 360-degree ST in terms of safety and efficacy in patients with OAG.

Mini-canaloplasty as a modified technique for the surgical treatment of open-angle glaucoma

Authors present a modified surgical technique for canaloplasty without preparing the classical trabeculo-Descemet’s membrane (TDM) and having to close sutures. Twelve patients with open-angle glaucoma (OAG) (aged 58–77 years) received the modified technique, which does not require the deep scleral flap to be excised, an intrascleral lake to be created, or TDM dissection. After accessing the Schlemm’s canal (SC), cannulation and placement of the sutures are made similar to those in the classical canaloplasty. The conjunctiva is closed via bipolar diathermy. The mean intraocular pressure (IOP) before surgery was 18.0 ± 8 mmHg, and the mean number of anti-glaucoma medications taken was 3 ± 1. Mean IOP at the end of the observation period (18.0 ± 6.0 months) was reduced by 23% (15.5 ± 4.1 mmHg), while the mean number of medications taken was reduced to 0.25 ± 1.0. In all eyes, the SC was successively opened, with no cheese-wiring. Adverse events included microhyphaema, mild corneal oedema, and folds in the TDM. The eyes recovered spontaneously within a few days after the procedure. The mini-canaloplasty technique may reduce the risk of complications associated with classical canaloplasty while effectively lowering the IOP in patients with OAG.

Comparison of ExPress Implantation and Partial Deep Sclerectomy Combined with ExPress Implantation and Simultaneous Phacoemulsification

Background

To compare the effectiveness and safety profile of ExPress implantation versus partial deep sclerectomy combined with ExPress implantation and simultaneous phacoemulsification.

Patients and Methods

A prospective, randomized control study with 24-month follow-up was performed. 114 eyes were included, of which 42 eyes underwent phacoemulsification with simultaneous implantation of the Ex-Press device (ExPress), and deep sclerectomy with phacoemulsification and simultaneous implantation of the Ex-Press device (DS-ExPress) was performed in 72 eyes. The main outcome measures were intraocular pressure (IOP), corrected distance visual acuity (CDVA), the number of antiglaucoma medications, and the rate of complications. Surgical success was defined as complete (without antiglaucoma medications) with IOP ≤18 mmHg in criterion A, IOP ≤16 mmHg in criterion B, and IOP ≤12 mmHg in criterion C. Satisfactory success was defined as the same IOP levels for individual criteria with a maximum of 2 antiglaucoma medications.

Results

Before the procedure, mean IOP in the ExPress group was 17.5 ± 4.7 mmHg; after 24 months, it decreased by 13% to 16.0 ± 3.0 mmHg (P < 0.05). In the DS-ExPress group, mean IOP reduced from 16.3 ± 4.4 mmHg to 14.3 ± 3.3 mmHg (P < 0.05), which was a 9% reduction compared to the initial value. In the DS-ExPress group, 65.9% of the patients did not use topical pharmacotherapy, and the same is true for 29.2% of the ExPress group (P=0.004).

Conclusions

This modification is efficient in surgical treatment of glaucoma, especially when very low postoperative IOP is needed. A less amount of antiglaucoma medicines are needed.

Scleral and conjunctival features in patients with rhegmatogenous retinal detachment undergoing scleral buckling: an anterior segment optical coherence tomography and in vivo confocal microscopy study

PURPOSE

To investigate the scleral and conjunctival features in patients with rhegmatogenous retinal detachment (RRD) undergoing scleral buckling (SB), using anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM).

METHODS

Twenty RRD eyes were consecutively enrolled. AS-OCT was performed at RRD diagnosis (RRD-D) and day 1, week 1, month 1 and month 6 after SB to evaluate the sclera, in the affected and unaffected quadrants (AQ, UQ). IVCM was performed at RRD-D, and at month 1 and month 6, to evaluate the conjunctiva in AQ and UQ. The main outcomes were as follows: mean intra-scleral hypo-reflective spaces area (MIHSA) at AS-OCT; mean density and area of microcysts (MMD, MMA) at IVCM; and intra-ocular pressure (IOP). The relations between MIHSA, MMA, MMD and IOP were evaluated.

RESULTS

Rhegmatogenous retinal detachment- diagnosis (RRD-D) overall-mean intra-scleral hypo-reflective spaces (MISHA), -MMD and -MMA were significantly higher in affected eye (AE) compared with UE (p < 0.05) and in AQ compared with UQ (p < 0.05). After SB, overall-, AQ- and UQ-MISHA further increased (p < 0.05), whereas overall-MMD and -MMA did not change. At all follow-up, AQ and UQ parameters did not show significant differences between them. RRD-D IOP was 14.3 ± 2.8 and 15.5 ± 2.7 mmHg in the AE and UE, respectively (p < 0.05). After SB, week-1, month-1 and -6 IOP was significantly lower than RRD-D (p < 0.05). Rhegmatogenous retinal detachment- diagnosis (RRD-D), 1- and 6-month overall and AQ-MISHA and AQ-MMD negatively correlated with IOP (p < 0.05).

CONCLUSION

Rhegmatogenous retinal detachment (RRD) and SB induced scleral and conjunctival changes that suggested an activation of fluid outflow through the entire unconventional aqueous humour pathway; these modifications may in part account for the relative hypotony after RRD and SB.

How many aqueous humor outflow pathways are there?

The aqueous humor (AH) outflow pathways definition is still matter of intense debate. To date, the differentiation between conventional (trabecular meshwork) and unconventional (uveoscleral) pathways is widely accepted, distinguishing the different impact of the intraocular pressure on the AH outflow rate. Although the conventional route is recognized to host the main sites for intraocular pressure regulation, the unconventional pathway, with its great potential for AH resorption, seems to act as a sort of relief valve, especially when the trabecular resistance rises. Recent evidence demonstrates the presence of lymphatic channels in the eye and proposes that they may participate in the overall AH drainage and intraocular pressure regulation, in a presumably adaptive fashion. For this reason, the uveolymphatic route is increasingly thought to play an important role in the ocular hydrodynamic system physiology. As a result of the unconventional pathway characteristics, hydrodynamic disorders do not develop until the adaptive routes cannot successfully counterbalance the increased AH outflow resistance. When their adaptive mechanisms fail, glaucoma occurs. Our review deals with the standard and newly discovered AH outflow routes, with particular attention to the importance they may have in opening new therapeutic strategies in the treatment of ocular hypertension and glaucoma.

Evaluation of Long-term Anatomic Changes Following Canaloplasty With Anterior Segment Spectral-domain Optical Coherence Tomography and Ultrasound Biomicroscopy

BACKGROUND

To analyze long-term structural changes in conjunctiva, sclera and Schlemm canal (SC) with anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM) following uncomplicated canaloplasty.

MATERIALS AND METHODS

Fifteen patients with planned canaloplasty and no intraoperative complications were included in this prospective study. AS-OCT images were acquired at 1, 3, 6 months and at a long-term time point (20±4.9 mo) postsurgery. UBM images were acquired at 3, 6 months and long-term after canaloplasty. The surgical site was evaluated for the presence of SC, transscleral filtration, a scleral lake, and the visibility of intra-Schlemm sutures. The SC's height and width were measured at the 3 and 9 o'clock limbus position.

RESULTS

Following canaloplasty, the intraocular pressure was successfully reduced from 23.43±5.52 to 12.6±1.78 mm Hg (P<0.0001) at the final control visit. Topical medication was reduced from 2.9±1.1 to 0.4±0.6 over the same period. SC's increase in height was higher than that in width at the last visit (height: +351%, P=0.0004, width: +144%, P=0.002). With the UBM the SC was easily identifiable by the reflection of the tractions sutures in 75% of the patients at the last visit. Transscleral filtration was detectable in 42% of the patients at the last visit using AS-OCT and a scleral lake was still detectable by OCT in 25% of the patients and even in 42% of the patients by UBM.

CONCLUSIONS

Persisting anatomic changes of SC, a transscleral filtration and a scleral lake can be recorded by AS-OCT and UBM long-term after successful canaloplasty.

Three-dimensional Laser Scanning Confocal Analysis of Conjunctival Microcysts in Glaucomatous Patients Before and After Trabeculectomy

BACKGROUND/AIM

In glaucoma, conjunctival epithelial microcysts (CEM) have been extensively investigated by means of laser scanning confocal microscopy. In the present case series, we examined eight glaucomatous patients undergoing trabeculectomy to obtain a 3-dimensional (3-D) characterization of CEM.

MATERIALS AND METHODS

Image acquisition was performed in z-scan automatic volume mode by Heidelberg Retina Tomograph III/Rostock Cornea Module and a series of 40 images of 300×300 μm (384×384 pixels) to a maximum depth of 40 μm were acquired throughout the upper bulbar conjunctiva before (at the site planned for surgery) and eight weeks after trabeculectomy. The 3-D volume tissue reconstruction with maximal size of 300×300×40 μm was obtained.

RESULTS

In the enface view, CEM appeared as empty, optically clear, round or oval shaped sub-epithelial structures. The 3-D spatial reconstruction showed microcysts as oval-shaped and optically clear elements, which were close, but clearly separated from the epithelium. CEM were embedded in the extra-cellular spaces and located about 10 μm below the epithelial surface. After trabeculectomy, CEM increased density and area especially along the horizontal axis.

CONCLUSION

The 3-D in vivo confocal reconstruction of CEM permits for better clarification of their microscopic anatomy and patho-physiological significance, confirming their involvement in AH flow through the bleb-wall after filtration surgery for glaucoma.

High-Intensity Focused Ultrasound Circular Cyclocoagulation in Glaucoma: A Step Forward for Cyclodestruction?

The ciliary body ablation is still considered as a last resort treatment to reduce the intraocular pressure (IOP) in uncontrolled glaucoma. Several ablation techniques have been proposed over the years, all presenting a high rate of complications, nonselectivity for the target organ, and unpredictable dose-effect relationship. These drawbacks limited the application of cyclodestructive procedures almost exclusively to refractory glaucoma. High-intensity focused ultrasound (HIFU), proposed in the early 1980s and later abandoned because of the complexity and side effects of the procedure, was recently reconsidered in a new approach to destroy the ciliary body. Ultrasound circular cyclocoagulation (UC³), by using miniaturized transducers embedded in a dedicated circular-shaped device, permits to selectively treat the ciliary body in a one-step, computer-assisted, and non-operator-dependent procedure. UC³ shows a high level of safety along with a predictable and sustained IOP reduction in patients with refractory glaucoma. Because of this, the indication of UC³ was recently extended also to naïve-to-surgery patients, thus reconsidering the role and timing of ciliary body ablation in the surgical management of glaucoma. This article provides a review of the most used cycloablative techniques with particular attention to UC³, summarizing the current knowledge about this procedure and future possible developments.

Modified 360-degree Suture Trabeculotomy for Pseudoexfoliation Glaucoma: 12-Month Results

PURPOSE

We aimed to evaluate the 12-month results of a modified 360-degree suture trabeculotomy (ST) technique in patients with pseudoexfoliation glaucoma (XFG).

PATIENTS AND METHODS

The modified 360-degree ST was performed on 20 eyes of 20 consecutive patients with XFG resistant to maximal topical treatment. In 8 patients, ST was combined with phacoemulsification. The main outcome measures were the surgical success rate, the mean postoperative intraocular pressure (IOP), the number of antiglaucoma medications, and the operative complications.

RESULTS

The baseline IOP (26.55 ± 8.91) and medications (3.15 ± 0.81) decreased significantly to 10.90 ± 2.73 mm Hg and 0.30 ± 0.80, respectively, at 12 months postoperatively (P<0.001). The magnitude of IOP reduction was 58.9%. Complete and qualified success rates were 68.4% and 94.7%, respectively. The entire circumference of Schlemm's canal was opened successfully in all cases. Hyphema, perforation of the trabeculodesmetic window, posterior synechia, peripheral anterior synechia, and a transient elevation of the IOP were noted. The results are comparable to our 6-month results and other previously published results for circumferential trabeculotomy.

CONCLUSIONS

The modified 360-degree ST provides a feasible choice in patients with XFG with a reasonable rate of complications. The 12-month success rates are promising. It can also be combined effectively with the current cataract surgery.

Evaluation of early anatomical changes following canaloplasty with anterior segment spectral-domain optical coherence tomography and ultrasound biomicroscopy

PURPOSE

To analyse structural changes in conjunctiva, sclera and Schlemm's canal (SC) following canaloplasty with optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM).

METHODS

Fifteen patients undergoing canaloplasty were included in this prospective study. AS-OCT images were acquired pre- and 1, 7, 30 and 90 days postoperatively. UBM was performed 3 months postoperatively. The surgical site was evaluated for the presence of SC, transscleral filtration, a scleral lake and the visibility of intra-Schlemm-sutures. The height and width of SC were measured at the 3 and 9 o'clock limbus position.

RESULTS

After canaloplasty, SC was detectable with AS-OCT in 93% of the patients on day 1. The increase in height was higher than that in width (height: +369%, p = 0.0004, width: +152%, p = 0.002). IOP was negatively correlated to SC's width 1 week postoperatively (r = -0.63, p = 0.04) and to SC's height until 3 months (r = -0.66, p = 0.02) postoperatively. Using UBM, a reflection of the traction sutures indicated SC's position in all patients. Transscleral filtration was found in all patients using AS-OCT, demonstrating a peak 1 week postoperatively. At 3 months, a scleral lake could be visualized in 50% and 83% of patients using AS-OCT and UBM, respectively.

CONCLUSIONS

AS-OCT offers a high resolution for imaging superficial conjunctival areas and SC after canaloplasty, whereas UBM is capable of detecting deeper structures such as scleral lakes or intra-canal-sutures. The results imply a correlation of the dilation of SC with the IOP-lowering effect and an early pronounced transscleral filtration following canaloplasty.

[Revision procedures after canaloplasty]

Canaloplasty is a recently introduced non-penetrating surgical technique for glaucoma, which seeks to improve the natural outflow of aqueous humor through Schlemm's canal and the collector channels. Just as in all forms of glaucoma surgery there are a certain number of failures of the procedure and further surgery is often needed to reduce the intraocular pressure in these cases. This article describes some of the revision procedures after canaloplasty.

Canaloplasty: Current Value in the Management of Glaucoma

Canaloplasty is a nonpenetrating blebless surgical technique for open-angle glaucoma, in which a flexible microcatheter is inserted within Schlemm's canal for the entire 360 degrees. When the microcatheter exits the opposite end, a 10-0 prolene suture is tied and it is then withdrawn, by pulling microcatheter back through the canal in the opposite direction. Ligation of prolene suture provides tension on the canal and facilitates aqueous outflow. The main advantage of canaloplasty is that this technique avoids the major complications of fistulating surgery related to blebs and hypotony. Currently, canaloplasty is performed in glaucoma patients with early to moderate disease and combination with cataract surgery is a suitable option in patients with clinically significant lens opacities.

Uveo-scleral outflow pathways after ultrasonic cyclocoagulation in refractory glaucoma: an anterior segment optical coherence tomography and in vivo confocal study

AIMS

To evaluate, using anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM), the uveo-scleral aqueous humour (AH) outflow pathways after ultrasonic circular cyclocoagulation (UCCC).

METHODS

Forty-four patients with refractory glaucoma underwent 4 or 6 s UCCC (group 1, 24 eyes; group 2, 20 eyes). UCCC was successful when the preoperative intraocular pressure (IOP) reduced by one-third. AS-OCT and IVCM were performed at baseline and at month 1 to evaluate the sclera and conjunctiva. The main outcomes were mean intra-scleral hyporeflective spaces area (MIHSA: mm²) at AS-OCT, mean density and area of conjunctival microcysts (MMD: cysts/mm²; MMA: µm²) at IVCM. The relations between MIHSA, MMA and MMD with IOP were analysed.

RESULTS

Mean baseline IOP was 26.9±2.8 mm Hg in group 1 and 27.5±4.0 in group 2. Intra-scleral hyporeflective spaces and microcysts were observed in both groups, without significant differences in MIHSA, MMA and MMD. At month 1, UCCC was successful in 63.6% of patients (41.6% in group 1, 80% in group 2), and IOP reduced to 18.8±3.2 (30.1%) and 17.1±2.7 mm Hg (38.7%), respectively (p<0.001). MIHSA showed a twofold and threefold increase in group 1 and 2 (p<0.05), with a significant difference between groups (p<0.05). MMA and MMD increased in both groups (p<0.05), with values higher in group 2 (p<0.05). Significant relations were found between MIHSA and IOP in both groups (p<0.01).

CONCLUSIONS

UCCC induced anatomical modifications of sclera and conjunctiva, which suggested that the trans-scleral AH outflow enhancement is one of the possible mechanisms exploited by ultrasounds to reduce IOP.

Emerging surgical therapy in the treatment of glaucoma

There is general consensus that surgery gives a better intraocular pressure (IOP) control than medical therapy, but surgery may be affected by complications and failures, and for this reason nowadays, it is reserved to advanced or clearly progressive glaucoma. In recent years, there have been a lot of efforts to enhance safety and efficacy of conventional surgery as to find new techniques more safer and more effective. Actually, this is a field in rapid evolution, and we have a great number of innovative procedures, often working on complete different basis. These procedures are classified according to their mechanism of action and the type of surgical approach, in order to clearly understand of what we are speaking about. From a general point of view, surgical procedures may be divided in procedures that increase outflow and procedures that reduce aqueous production: most of these procedures can be performed with an ab externo or an ab interno approach. The ab interno approach has great advantages and enormous potential of development; probably, its diffusion will be facilitated by the development of new devices for angle visualization. Nevertheless, it is important to remember that actually none of the new procedures has been validated in large controlled clinical trials and none of the new procedures is indicated when IOP target is very low.

Complete 360° circumferential gonioscopic optical coherence tomography imaging of the iridocorneal angle

Clinically, gonioscopy is used to provide en face views of the ocular angle. The angle has been imaged with optical coherence tomography (OCT) through the corneoscleral limbus but is currently unable to image the angle from within the ocular anterior chamber. We developed a novel gonioscopic OCT system that images the angle circumferentially from inside the eye through a custom, radially symmetric, gonioscopic contact lens. We present, to our knowledge, the first 360° circumferential volumes (two normal subjects, two subjects with pathology) of peripheral iris and iridocorneal angle structures obtained via an internal approach not typically available in the clinic.

Anterior segment optical coherence tomography imaging of conjunctival filtering blebs after glaucoma surgery

Time domain (TD) and spectral domain (SD) optical coherence tomography (OCT) are cross-sectional, noncontact, high-resolution diagnostic modalities for posterior and anterior segment (AS) imaging. The AS-OCT provides tomographic imaging of the cornea, iris, lens, and anterior chamber (AC) angle in several ophthalmic diseases. In glaucoma, AS-OCT is utilized to evaluate the morphology of AS structures involved in the pathogenesis of the disease, to obtain morphometric measures of the AC, to evaluate the suitability for laser or surgical approaches, and to assess modifications after treatment. In patients undergoing surgery, AS-OCT is crucial in the evaluation of the filtering bleb functionality, permitting a combined qualitative and quantitative analysis. In this field, AS-OCT may help clinicians in distinguishing between functioning and nonfunctioning blebs by classifying their macroscopic morphology, describing bleb-wall features, bleb cavity, and scleral opening. This information is critical in recognizing signs of filtration failure earlier than the clinical approach and in planning the appropriate timing for management procedures in failing blebs. In this review, we summarize the applications of AS-OCT in the conjunctival bleb assessment.

In vivo laser scanning confocal microscopy of the ocular surface in glaucoma

Over the past decade, knowledge about the ocular surface in glaucoma has significantly increased through the use of in vivo laser scanning confocal microscopy (LSCM). This in vivo imaging method can show modifications at the cellular level induced by anti-glaucoma drugs on ocular surface structures and adnexa in the eye. High-quality images of the conjunctiva, cornea, limbus, meibomian glands, and lymphoid structures during therapy can be obtained. In addition, LSCM opened new fields of research on the patho-physiology of aqueous humor (AH) hydrodynamics in untreated, and in medically or surgically treated glaucomatous patients. In these conditions, an enhancement of the trans-scleral AH outflow contributed to clarification of the mechanism of action of different anti-glaucoma medications and surgical approaches. Finally, the use of LSCM represented a huge advance in evaluation of bleb functionality after filtration surgery, defining the hallmarks of AH filtration through the bleb-wall and distinguishing functional from nonfunctional blebs. Thus, signs seen with LSCM may anticipate clinical failure, guiding the clinician in planning the appropriate timing of the various steps in bleb management. In this review we summarize the current knowledge about in vivo LSCM of the ocular surface in glaucoma.

Trans-conjunctival aqueous humor outflow in glaucomatous patients treated with prostaglandin analogues: an in vivo confocal microscopy study

PURPOSE

To analyze, using in vivo laser scanning confocal microscopy (LSCM), the conjunctival features in glaucomatous patients receiving prostaglandin analogues (PGA).

METHODS

Eighty eyes of 80 consecutive glaucomatous patients naive for therapy were enrolled; 30 eyes of 30 healthy subjects served as a control. Patients were randomized to: preservative-free (PF) and preserved latanoprost (groups 1 and 2, respectively), PF and preserved timolol (groups 3 and 4), and controls to vehicle of latanoprost or physiological buffered saline solution (groups 5 and 6). All subjects underwent LSCM of bulbar conjunctiva at baseline and 3 months after initiating therapy. The main outcomes were: mean density (MMD: cysts/mm(2)) and mean area (MMA: cysts/mm(2)) of epithelial microcysts. The relations between MMA and MMD with intraocular pressure (IOP), age, and mean defect (MD), were analyzed.

RESULTS

At baseline, microcysts were found in all subjects. At month three, MMD did not change in all groups (p > 0.05). MMA significantly increased only in group 1 from 2,158.81 ± 524.09 to 3,877.77 ± 867.31, and in group 2 from 2,019.71 ± 541.03 to 5,560.39 ± 1,176.14, with values significantly higher in group 2 (p < 0.001). Significant relations were not found between MMD and MMA with IOP, MD, and age (p > 0.05).

CONCLUSIONS

PGA increased MMA in therapy-naive glaucomatous patients, indicating a possible enhancement of the trans-conjunctival aqueous humor outflow. Therefore, conjunctiva seems an additional target tissue to evaluate the hydrodynamic pathways in glaucoma and modifications induced by medical therapy.

IOP elevation reduces Schlemm's canal cross-sectional area

PURPOSE

Previously, we demonstrated reduced Schlemm's canal cross-sectional area (SC-CSA) with increased perfusion pressure in a cadaveric flow model. The purpose of the present study was to determine the effect of acute IOP elevation on SC-CSA in living human eyes.

METHODS

The temporal limbus of 27 eyes of 14 healthy subjects (10 male, 4 female, age 36 ± 13 years) was imaged by spectral-domain optical coherence tomography at baseline and with IOP elevation (ophthalmodynamometer set at 30-g force). Intraocular pressure was measured at baseline and with IOP elevation by Goldmann applanation tonometry. Vascular landmarks were used to identify corresponding locations in baseline and IOP elevation scan volumes. Schlemm's canal CSA at five locations within a 1-mm length of SC was measured in ImageJ as described previously. A linear mixed-effects model quantified the effect of IOP elevation on SC-CSA.

RESULTS

The mean IOP increase was 189%, and the mean SC-CSA decrease was 32% (P < 0.001). The estimate (95% confidence interval) for SC-CSA response to IOP change was -66.6 (-80.6 to -52.7) μm(2)/mm Hg.

CONCLUSIONS

Acute IOP elevation significantly reduces SC-CSA in healthy eyes. Acute dynamic response to IOP elevation may be a useful future characterization of ocular health in the management of glaucoma.

Canaloplasty in open-angle glaucoma surgery: a four-year follow-up

Canaloplasty is a new nonperforating surgical technique for open-angle glaucoma, in which a microcatheter is inserted within Schlemm's canal for the entire 360 degrees. A 10-0 prolene suture, which is tied to the distal tip of the microcatheter, is then positioned and left tensioned in Schlemm's canal, thus facilitating aqueous outflow through natural pathways. A small amount of viscoelastic agent is delivered in Schlemm's canal while the catheter is withdrawn. The mid-term results are very promising. Based on our cohort of 214 patients, the percentages of eyes that obtained postoperative IOP ≤ 21 mmHg, ≤18 mmHg, and ≤16 mmHg with or without medical therapy after 2 and 3 years were 88.7%, 73.7%, and 46.2% (2 years); 86.2%, 58.6%, and 37.9% (3 years), respectively. The most frequent complications observed included hyphema; descemet membrane detachment; IOP spikes; and hypotony. The advantages of canaloplasty over trabeculectomy include (1) no subconjunctival bleb; (2) no need for antimetabolites; (3) fewer postoperative complications; and (4) a simplified follow-up. The disadvantages include the following: (1) a long and rather steep surgical learning curve; (2) the need of specific instruments; (3) average postoperative IOP levels tend not to be very low; and (4) impossibility to perform the entire procedure in some cases.