Dilation of Schlemm's canal in viscocanalostomy: comparison of 2 viscoelastic substances

Viscocanalostomy with Mitomycin-C: A Preliminary Study

Purpose

To compare the results of viscocanalostomy with and without mitomycin-C (MMC).

Methods

Retrospective results of 15 standard viscocanalostomy (VCO) operations (Group 1) were compared with the prospective results of 15 VCO operations performed with intraoperative adjunctive MMC (Group 2). MMC (0.2 mg/mL) was applied over and under the superficial scleral flap for 3 minutes in Group 2 before the deep flap was prepared. Each patient was followed up for at least 1 year, and results of examinations in the first 12 months were used in the statistical comparison of the two groups. Surgical success was defined as intraocular pressure (IOP) ≤ 18 mmHg.

Results

Pr eoperative mean intraocular pressures (IOP) in Group 1 and Group 2 wer e 35.3±11.0 and 39.1±8.9, respectively. Mean IOP levels at the 12th month were 14.4±2.6 and 11.9±4.0, respectively, showing a significant decrease in both groups (p<0.001). Postoperative IOP course appeared to be lower in the MMC group, however, the difference was not statistically significant (p=0.554). Complete success rates without medications were 40% in Group 1 and 67% in Group 2. No significant difference was found between the two groups in terms of early and late postoperative complications, pre- and postoperative number of antiglaucoma medications, and surgical success rates at the end of the study period (p>0.05 for all). A significant difference was verified between the two groups of eyes considering the conjunctival bleb types, as low-lying, localized blebs were the most frequent type in Group 1 and thin-walled, avascular blebs were more predominant in the MMC group (p=0.004).

Conclusions

Intraoperative adjunctive MMC use might improve the long-term results of viscocanalostomy by facilitating subconjunctival filtration and might widen the indication range of the technique.

Outcomes of Nd: YAG Goniopuncture After Viscocanalostomy/Phacoviscocanalostomy

PURPOSE

The aim of this study is to evaluate the safety and efficacy of laser goniopuncture (LGP) to lower intraocular pressure (IOP) post-viscocanalostomy (VC)/phacoviscocanalostomy (PVC). Outcomes include: IOP reduction from pre-LGP levels and the need for further topical antiglaucomatous medication or surgery.

PATIENTS AND METHODS

A total of 541 eyes that underwent VC/PVC between 2009 and 2012, at the Stanley eye unit in Abergele were included in the study.

INCLUSION CRITERIA

All patients who had LGP at any timepoint after VC/PVC when target IOP was not achieved +/- progression in visual field with at least 6 months of follow-up data.Statistical analysis was performed on IOP values pre- and post-LGP, involving χ, Fischer exact, Mann-Whitney U, and Wilcoxon tests. A P-value of <0.05 was accepted as the level of significance.

RESULTS

Of the 515 included eyes, 136 (26%) required LGP after a mean of 15.11±9.73 months after surgery (95% confidence interval, 13.46-16.76 mo), ranging from 1 to 42 months. LGP reduced IOP significantly from a mean of 22.92±5.80 to 17.08±5.30 mm Hg immediately for all eyes, a reduction of 5.84 mm Hg (or a 25% reduction) (P<0.0001). IOP significantly reduced in the VC group with a mean reduction of 7.60 mm Hg compared with 4.85 mm Hg in the PVC group immediately after the procedure (P=0.0038). LGP was required sooner in the VC group compared with PVC, 11.35 and 14.57 months, respectively (P=0.0393). A total of 69 (62%) eyes were commenced on topical IOP-lowering medications, mean 7.26±6.41 months after LGP.

CONCLUSIONS

This study supports previous evidence that LGP enhances the IOP-lowering success of VC/PVC. The advantages of LGP are that it is a minimally invasive clinic-based procedure with a low complication rate.

Spectral-domain optical coherence tomographic assessment of Schlemm's canal in Chinese subjects with primary open-angle glaucoma

PURPOSE

To evaluate in vivo features of Schlemm's canal (SC) in patients with primary open-angle glaucoma (POAG) with spectral-domain optical coherence tomography (SD-OCT) and to investigate the relationship of SC size with intraocular pressure (IOP) and glaucoma severity.

DESIGN

Prospective, comparative study.

PARTICIPANTS

Fifty Chinese patients with newly diagnosed POAG who had not undergone surgery and 50 normal Chinese subjects from a population-based, cross-sectional study in Shanghai.

METHODS

All participants underwent SD-OCT. The diameter and area of SC were examined in the temporal and nasal sections and measured with customized software.

MAIN OUTCOME MEASURES

Patient demographics, repeatability and reproducibility assessed with the coefficient of variation (CV) and the intraclass correlation coefficient (ICC), SC parameters and their correlation with IOP, and the mean deviation (MD) of the visual field were analyzed.

RESULTS

The percentage of sections in which SC was observable was similar between eyes with POAG and normal eyes, and ranged from 78% to 86%. For intraobserver repeatability, the CV and ICC values were 7.9% and 0.97 for diameter, and 13.8% and 0.83 for area, respectively. For interobserver repeatability, the CV and ICC values were 13.6% and 0.89 for diameter, and 13.4% and 0.80 for area, respectively. Significant differences between the 2 groups were found for the average SC area (11332 ± 2015 μm(2) vs. 13991 ± 1357 μm(2); P<0.001), but not for the SC diameter (40.2 ± 7.1 μm vs. 45.2 ± 4.0 μm; P = 0.195). In addition, the mean IOP values correlated well only with the SC area (ρ = -0.674, P<0.001), not with the SC diameter (ρ = -0.103, P = 248). No significant correlations were found between the MD values and the SC parameters.

CONCLUSIONS

Eyes with POAG have a decreased SC area compared with normal eyes. A correlation between the SC area and the IOP also was observed. However, the degree of glaucoma damage was not consistently associated with the SC area. Spectral-domain OCT could be used for investigating SC changes in patients with glaucoma.

Clinical options for the reduction of elevated intraocular pressure

Elevated IOP in clinical practice is usually seen in glaucoma or ocular hypertension. Glaucoma affects 60 million people worldwide and 8.4 million are bilaterally blind from this chronic disease.1 Options for reducing IOP rely on pharmacological agents, laser treatments and surgery which may be penetrating or non-penetrating. The last twenty years has seen significant changes in all of these strategies. This review aims to cover these clinical options and introduce some of the new technologies currently in development for the clinical lowering of IOP.

Use of viscoelastic substance in ophthalmic surgery - focus on sodium hyaluronate

Among viscoelastic substances, sodium hyaluronate has become the most popular for intraocular surgeries since the introduction of Healon^® (sodium hyaluronate 1%, 4 × 10⁶ daltons) in 1979. This review focuses on the recent development of a new generation of sodium hyaluronate agents with new rheologic properties and the relevant new techniques used in cataract, glaucoma, corneal, and vitreoretinal surgeries. The introduction of sodium hyaluronate agents with different rheologic properties has improved the safety and reliability of intraocular surgeries. Although there have been numerous studies reporting the effectiveness of viscoelastic substances in intraocular surgeries, rigorous validation by multi-center randomized control trials is lacking in many cases. At present, no single viscoelastic agent is most suitable to all of the various intraocular surgical techniques. Therefore, ophthalmologic surgeons should keep up with recent developments of viscoelastic agents and relevant surgical techniques for better patient care.

Identification and assessment of Schlemm's canal by spectral-domain optical coherence tomography

PURPOSE

Measurements of human Schlemm's canal (SC) have been limited to histologic sections. The purpose of this study was to demonstrate noninvasive measurements of aqueous outflow (AO) structures in the human eye, examining regional variation in cross-sectional SC areas (on/off collector channel [CC] ostia [SC/CC] and nasal/temporal) in the eyes of living humans.

METHODS

SC was imaged by spectral-domain optical coherence tomography with a 200-nm bandwidth light source. Both eyes of 21 healthy subjects and one glaucomatous eye of three subjects were imaged nasally and temporally. Contrast and magnification were adjusted to maximize visualization. Cross-sectional SC on and off SC/CC was traced three times by two independent masked observers using ImageJ (ImageJ 1.40g, http://rsb.info.nih.gov/ij/ Wayne Rasband, developer, National Institutes of Health, Bethesda, MD). The mean SC area was recorded. A linear mixed-effects model was used to analyze eye, nasal/temporal laterality, and SC area on or off SC/CC.

RESULTS

SC area was significantly larger on SC/CCs than off (12,890 vs. 7,391 micorm(2), P < 0.0001) and was significantly larger on the nasal side than on the temporal (10,983 vs. 8,308 micorm(2), P = 0.009). SC areas were significantly smaller in glaucoma patients than in normal subjects, whether pooled (P = 0.0073) or grouped by on (P = 0.0215) or off (P = 0.0114) SC/CC.

CONCLUSIONS

Aqueous outflow structures, including SC and CCs, can be noninvasively assessed in the human eye. These measurements will be useful in physiological studies of AO and will be clinically useful in the determination of the impact of glaucoma therapies on IOP as well as presurgical planning.

Nonpenetrating glaucoma surgery

Nonpenetrating glaucoma surgeries have been developed in recent years in order to improve the safety of conventional filtering procedures. The goal of nonpenetrating filtering procedures is to reduce intraocular pressure by enhancing the natural aqueous outflow channels, while reducing outflow resistance located in the inner wall of the Schlemm's canal and the juxtacanalicular trabecular meshwork. In the last few years viscocanalostomy and deep sclerectomy with external trabeculectomy have become the most popular nonpenetrating filtering procedures. Both involve removal of a deep scleral flap, the external wall of Schlemm's canal and corneal stroma behind the anterior trabeculum and Descemet's membrane, thus creating an intrascleral space. The aqueous humour leaves the anterior chamber through the intact trabeculo-Descemet's membrane into the scleral space, from where it will egress into different pathways. The technique is associated with a long learning curve. Published clinical trials comparing nonpenetrating glaucoma surgery to full-thickness trabeculectomy have a consensus on the superior safety profile of nonpenetrating glaucoma surgery but are not in agreement when it comes to efficacy, where conflicting results have been found. This article reviews the nonpenetrating surgical techniques, mechanisms of action, indications, contraindications, complications, and results.

Combined viscocanalostomy-trabeculectomy for management of far-advanced glaucoma: evaluation of the early postoperative course

BACKGROUND AND OBJECTIVE

To study the early postoperative efficacy and safety of combined viscocanalostomy with trabeculectomy (VISCO-TRAB) for treating far-advanced glaucoma.

PATIENTS AND METHODS

Patients with far-advanced glaucoma scheduled for glaucoma surgery were enrolled in the study. Surgery included viscocanalostomy until Schlemm's canal was deroofed and dilated with viscoelastic, followed by penetrating corneotrabeculectomy, peripheral iridectomy, and tight closure of lamellar flap. Patients with severe glaucoma who were treated with trabeculectomy only (TRAB) in the preceding year were used for comparison.

RESULTS

The study included 39 eyes in the VISCO-TRAB group and 40 eyes in the TRAB group. Mean intraocular pressure was significantly lower in the VISCO-TRAB group during the early postoperative period (P < .05). The postoperative course was less eventful in the VISCO-TRAB group with minimal hypotony or suture lysis-related complications.

CONCLUSION

During the early postoperative period, VISCO-TRAB proved efficacious and safe in reducing intraocular pressure to target levels in patients with far-advanced glaucoma.

Trabecular bypass: effect of schlemm canal and collector channel dilation

PURPOSE

To theorize the effect of Schlemm canal (SC) and/or collector channel (CC) dilation combined with a trabecular bypass on intraocular pressure (IOP) in eyes with primary open angle glaucoma.

METHODS

The elliptic shaped SC is dilated in conjunction with a trabecular bypass and its expanded height is largest at the bypass and linearly deceases to the nondilated height over the dilated circumferential length. The CC dilation is modeled with a reduced outflow resistance of second order polynomial over the same dilated length. Equations governing the pressure and circumferential flow in SC are solved numerically for both the unidirectional and bidirectional bypasses. The reduced IOP is deduced from the solution.

RESULTS

IOP is reduced substantially with moderate SC dilation from the normal height of 20 microm to 40 to 50 microm at the bypass; additional IOP reduction diminishes with further dilation. SC dilation is more effective for eyes with smaller SC. CC dilation also lower IOP significantly. With the trabecular bypass alone, the elevated IOP in primary open angle glaucoma is expected to drop to the mid-to-high teens. IOP can be further reduced by another 3 to 6 mm Hg with moderate SC and CC dilation. The circumferential length of dilated SC affects the efficacy of IOP reduction. In theory, the dilation of SC with a trabecular bypass is analogous to a partial trabeculotomy in terms of IOP reduction.

CONCLUSIONS

In theory, a moderate dilation of SC and CC in conjunction with a trabecular bypass reduces the IOP to the low-to-mid teens.

Viscocanalostomy Versus Trabeculectomy in Patients with Bilateral High-tension Glaucoma

Results of trabeculectomy (TE) and viscocanalostomy (VCO) were compared in a prospective randomised study in two fellow eyes of 22 consecutive patients with bilateral symmetrical high-tension glaucoma. Rates of overall surgical success with intraocular pressures (IOP) < or = 18 mm Hg with or without medications were 91 for the TE, and 95 for the VCO group after a mean follow-up of 18 months. Complete success rates without medications were 64 and 59 for TE and VCO groups, respectively (p = 0.750). Both procedures significantly reduced IOP, however, IOP course following trabeculectomy was significantly lower (p = 0.026). Rates of complications were not found to be different between the two groups of eyes, except for an apparent--though not significant (p = 0.066)--increase in cataract progression with TE. Various types of conjunctival blebs were detected in all eyes with surgical success in both groups, however, diffuse, elevated or multi-cystic functional blebs appeared to be more predominant in eyes with TE, compared to the VCO group in which low-lying, localised blebs had a higher incidence (p = 0.015). Viscocanalostomy was found to be a safe and effective filtration technique in patients with uncomplicated high-tension glaucoma, though IOP decrease was more pronounced with trabeculectomy.

Removal times for a dispersive and a cohesive ophthalmic viscosurgical device correlated with intraocular lens material

PURPOSE

To investigate the removal times of ophthalmic viscosurgical devices (OVDs) with different intraocular lens (IOL) designs and materials.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA, and Heidelberg IOL & Refractive Surgery Research Group, Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany.

METHODS

In a standardized laboratory setup, the Miyake-Apple posterior view video technique was used to evaluate OVD removal from capsular bags in human autopsy eyes implanted with poly(methyl methacrylate) (PMMA), silicone, and acrylic IOLs. The cohesive OVD ProVisc (sodium hyaluronate 1.0%) and the dispersive OVD Viscoat (sodium hyaluronate 3.0% and chondroitin sulfate 4.0%) were stained with fluorescein for better visualization. The open-sky preparation and an Alcon Series 20000 Legacy phaco machine with a flow rate of 25 mL/min and a vacuum setting of +500 mm Hg (maximum irrigation/aspiration) were used. The time needed for complete removal of the cohesive and dispersive OVDs with each IOL type was measured and analyzed statistically.

RESULTS

The mean removal times for both OVDs were as follows: Alcon MZ60BD PMMA IOL-25.0 seconds +/- 3.7 (SD) (Viscoat), 15.9 +/- 6.9 seconds (ProVisc); Alcon AcrySof MA60BM IOL-35.5 +/- 10.0 seconds (Viscoat), 25.6 +/- 4.7 seconds (ProVisc); Chiron/Bausch & Lomb C1043 silicone IOL-46.5 +/- 10.5 seconds (Viscoat), 17.3 +/- 2.1 seconds (ProVisc); AMO SI-30 silicone IOL-33.5 +/- 3.1 seconds (Viscoat), 15.3 +/- 6.3 seconds (ProVisc); and Pharmacia 912 silicone IOL-18.3 +/- 5.8 seconds (Viscoat), 19.8 +/- 4.3 seconds (ProVisc).

CONCLUSIONS

Differences in OVD removal times were detected. The removal time for the cohesive OVD correlated with the IOL material. Overall, the time needed for complete removal was significantly longer for the dispersive OVD than for the cohesive OVD.

Removal times and techniques of a viscoadaptive ophthalmic viscosurgical device

PURPOSE

To analyze removal techniques for Healon5 (sodium hyaluronate 2.3%).

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Charleston, South Carolina, USA, and Department of Ophthalmology, Ruprecht-Karls-University, Heidelberg, Germany.

METHODS

In a standardized laboratory setup, the Miyake-Apple posterior view video technique in human autopsy eyes was used to evaluate removal of an ophthalmic viscosurgical device (OVD) from capsular bags implanted with poly(methyl methacrylate), silicone, and acrylic intraocular lenses (IOLs). Healon5 was stained with fluorescein for better visualization. Open-sky preparation and an Alcon Legacy Series 20000 phaco machine with a flow rate of 25 mL/minute and a vacuum setting of +500 mm Hg (maximum irrigation/aspiration [I/A]) were used. With Technique 1, the I/A tip was placed on the center of the IOL and maximum aspiration was applied. With Technique 2 (modified rock 'n roll technique), the I/A tip was moved in quick circular movements on top of the IOL to break the OVD chains and facilitate aspiration.

RESULTS

With Technique 1, the mean removal time was 59.0 seconds +/- 23.1 (SD) and with Technique 2, 23.6 +/- 10.3 seconds (P =.004). The removal time of Healon5 correlated with the IOL material. With Technique 2, removal was fastest with silicone IOLs (13.5 +/- 2.1 seconds) followed by PMMA IOLs (17.5 +/- 2.1 seconds). With acrylic IOLs, remnants of the OVD trapped behind the IOL optic resulted in a longer removal time of 34.1 +/- 1.2 seconds.

CONCLUSIONS

Healon5 was completely removed from the capsular bag with the modified rock 'n roll technique. With acrylic IOLs, remnants can be trapped behind the optic and may be overlooked with an unstained OVD. Aspiration behind the optic is recommended with this IOL type.

Intracorneal hematoma with descemet membrane detachment after viscocanalostomy

PURPOSE

To describe a case of intracorneal hematoma with Descemet membrane detachment after viscocanalostomy.

DESIGN

Interventional case report.

METHODS

A 63-year-old with uncontrolled primary open-angle glaucoma underwent viscocanalostomy. During the introduction of hyaluronate 2.3% under the superficial flap, a limited lysis of Descemet membrane was observed.

RESULT

Slit-lamp biomicroscopy showed an intracorneal hematoma with Descemet membrane detachment 1 day after viscocanalostomy. The creation of an intentional break of Descemet membrane and descemetopexy using sulfur hexafluoride gas were performed. The cornea regained transparency after surgery.

CONCLUSIONS

Intracorneal hematoma with Descemet membrane detachment is a possible complication of viscocanalostomy.