Morphological variability of the trabecular meshwork in glaucoma patients: implications for non-perforating glaucoma surgery

Effect of Trabeculodescemetic Window Perforation in Deep Sclerectomy on Intraocular Pressure in Primary Congenital Glaucoma

INTRODUCTION

Primary congenital glaucoma causes vision loss if intraocular pressure is uncontrolled. Nonpenetrating deep sclerectomy is effective in treating primary congenital glaucoma. However, the effects of inadvertent trabeculodescemetic window perforation remain unclear.

METHODS

This retrospective cohort study included patients with primary congenital glaucoma who underwent nonpenetrating deep sclerectomy between 2014 and 2021. The perforation group had intraoperative trabeculodescemetic window perforations; the non-perforation group did not. The primary outcome was intraocular pressure between the groups over 15 months. The secondary outcomes included surgical success and complications.

RESULTS

The study included 74 eyes of 44 patients. The cohort comprised 31 perforated and 43 non-perforated eyes. Both groups showed significant intraocular pressure reduction without significant between-group differences in complete (68 vs. 77%), qualified (19 vs. 9%), or failed (13 vs. 14%) treatments. The median intraocular pressure decreased from 39 to 14 mmHg in the perforation group and 35 to 12 mmHg in the non-perforation group. Of the 74 treated eyes, 68 (92%) showed no complications.

CONCLUSIONS

An inadvertent trabeculodescemetic window perforation during nonpenetrating deep sclerectomy for primary congenital glaucoma did not significantly affect intraocular pressure outcomes compared to non-perforated cases over 15 months. Nonpenetrating deep sclerectomy reduced intraocular pressure regardless of intraoperative perforation in patients with primary congenital glaucoma. Perforation of the trabeculodescemetic window was associated with a low incidence of postoperative complications.

Efficacy and Safety of Deep Sclerectomy With the Esnoper Clip Implant for Uncontrolled Primary Open Angle Glaucoma: A 1 Year Prospective Study

PRCIS

Deep sclerectomy (DS) with the Esnoper Clip drainage implant in patients with uncontrolled primary open angle glaucoma (POAG) achieved a complete success rate of 87.2% at the 1-year follow-up.

PURPOSE

To investigate the efficacy and safety of DS followed by Esnoper Clip implantation in patients with uncontrolled POAG.

MATERIALS AND METHODS

In a prospective, consecutive, interventional study, we investigated 39 eyes of 35 patients with uncontrolled POAG who underwent DS with Esnoper Clip implantation. Complete ophthalmologic examinations including corrected visual acuity and intraocular pressure (IOP), were performed preoperatively, and at 1 day, at 1 week as well as at 1, 3, 6, 9, and 12 months postoperatively. Moreover, any goniopunctures and glaucoma medications required postoperatively were noted.

RESULTS

The mean preoperative IOP was 20.8±5.2 mm Hg and it decreased to 13.9±3.1 mm Hg at 1 year postoperatively ( P <0.001). The number of glaucoma medications decreased from 2.9±0.7 preoperatively to 0.3±0.8 after 1 year ( P <0.001). The complete success rate (IOP≤21 mm Hg without glaucoma medication) and the qualified success rate (IOP ≤21 mm Hg with or without glaucoma medication) were 87.2% and 94.9%, respectively. Goniopuncture was performed in 33.3% of cases. No significant corrected visual acuity changes were registered at the final follow-up. Perioperative complications consisted of 3 micro-perforations of the trabeculo-descemet membrane. Postoperative complications included: hyphema (6 eyes), hypotony (6 eyes), shallow anterior chamber (3 eyes), choroidal detachment (4 eyes)-all of which were resolved without surgical intervention during the first postoperative month-and conjunctival dehiscence, which required resuture (2 eyes).

CONCLUSION

Deep sclerectomy with the Esnoper Clip implant was safe and effectively lowered IOP in patients with uncontrolled POAG.

iPSCs-Based Therapy for Trabecular Meshwork

The trabecular meshwork (TM) of the eye serves as an essential tissue in controlling aqueous humor (AH) outflow and intraocular pressure (IOP) homeostasis. However, dysfunctional TM cells and/or decreased TM cellularity is become a critical pathogenic cause for primary open-angle glaucoma (POAG). Consequently, it is particularly valuable to investigate TM characteristics, which, in turn, facilitates the development of new treatments for POAG. Since 2006, the advancement in induced pluripotent stem cells (iPSCs) provides a new tool to (1) model the TM in vitro and (2) regenerate degenerative TM in POAG. In this context, we first summarize the current approaches to induce the differentiation of TM-like cells from iPSCs and compare iPSC-derived TM models to the conventional in vitro TM models. The efficacy of iPSC-derived TM cells for TM regeneration in POAG models is also discussed. Through these approaches, iPSCs are becoming essential tools in glaucoma modeling and for developing personalized treatments for TM regeneration.

Melt Electrowriting of Graded Porous Scaffolds to Mimic the Matrix Structure of the Human Trabecular Meshwork

The permeability of the human trabecular meshwork (HTM) regulates eye pressure via a porosity gradient across its thickness modulated by stacked layers of matrix fibrils and cells. Changes in HTM porosity are associated with increases in intraocular pressure and the progress of diseases such as glaucoma. Engineered HTMs could help to understand the structure–function relation in natural tissues and lead to new regenerative solutions. Here, melt electrowriting (MEW) is explored as a biofabrication technique to produce fibrillar, porous scaffolds that mimic the multilayer, gradient structure of native HTM. Poly(caprolactone) constructs with a height of 125–500 μm and fiber diameters of 10–12 μm are printed. Scaffolds with a tensile modulus between 5.6 and 13 MPa and a static compression modulus in the range of 6–360 kPa are obtained by varying the scaffold design, that is, the density and orientation of the fibers and number of stacked layers. Primary HTM cells attach to the scaffolds, proliferate, and form a confluent layer within 8–14 days, depending on the scaffold design. High cell viability and cell morphology close to that in the native tissue are observed. The present work demonstrates the utility of MEW for reconstructing complex morphological features of natural tissues.

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

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

Accurate Identification of the Trabecular Meshwork under Gonioscopic View in Real Time Using Deep Learning

PURPOSE

Accurate identification of iridocorneal structures on gonioscopy is difficult to master, and errors can lead to grave surgical complications. This study aimed to develop and train convolutional neural networks (CNNs) to accurately identify the trabecular meshwork (TM) in gonioscopic videos in real time for eventual clinical integrations.

DESIGN

Cross-sectional study.

PARTICIPANTS

Adult patients with open angle were identified in academic glaucoma clinics in both Taipei, Taiwan, and Irvine, California.

METHODS

Neural Encoder-Decoder CNNs (U-nets) were trained to predict a curve marking the TM using an expert-annotated data set of 378 gonioscopy images. The model was trained and evaluated with stratified cross-validation grouped by patients to ensure uncorrelated training and testing sets, as well as on a separate test set and 3 intraoperative gonioscopic videos of ab interno trabeculotomy with Trabectome (totaling 90 seconds long, 30 frames per second). We also evaluated our model's performance by comparing its accuracy against ophthalmologists.

MAIN OUTCOME MEASURES

Successful development of real-time-capable CNNs that are accurate in predicting and marking the TM's position in video frames of gonioscopic views. Models were evaluated in comparison with human expert annotations of static images and video data.

RESULTS

The best CNN model produced test set predictions with a median deviation of 0.8% of the video frame's height (15.25 μm) from the human experts' annotations. This error is less than the average vertical height of the TM. The worst test frame prediction of this model had an average deviation of 4% of the frame height (76.28 μm), which is still considered a successful prediction. When challenged with unseen images, the CNN model scored greater than 2 standard deviations above the mean performance of the surveyed general ophthalmologists.

CONCLUSIONS

Our CNN model can identify the TM in gonioscopy videos in real time with remarkable accuracy, allowing it to be used in connection with a video camera intraoperatively. This model can have applications in surgical training, automated screenings, and intraoperative guidance. The dataset developed in this study is one of the first publicly available gonioscopy image banks (https://lin.hs.uci.edu/research), which may encourage future investigations in this topic.

Schlemm's canal: the outflow 'vessel'

In a healthy eye, the aqueous humour (AH) flows via the ciliary body and trabecular meshwork into the collector channels, which carry it to the episcleral veins. In glaucoma, a heterogeneous group of eye disorders affecting approximately 60 million individuals worldwide, the juxtacanalicular meshwork offers greater resistance to the outflow of the AH, leading to an increase in outflow resistance that gradually results in elevated intraocular pressure (IOP). The present review comprehensively covers the morphology of Schlemm’s canal (SC) and AH pathways. The path of the AH from the anterior chamber through the trabeculum into suprascleral and conjunctival veins via collector channels is described, and the role of SC in the development of glaucoma and outflow resistance is discussed. Finally, channelography is presented as a precise method of assessing the conventional drainage pathway and facilitating localization of an uncollapsed collector and aqueous veins. Attention is also given to the relationship between aqueous and episcleral veins and heartbeat. Possible directions of future research are proposed.

A Review of Excisional Goniotomy Performed with the Kahook Dual Blade for Glaucoma Management

Aim

To review the published literature describing clinical outcomes of excisional goniotomy using the Kahook Dual Blade (KDB) for the management of glaucoma.

Background

A family of less invasive glaucoma procedures—including excisional goniotomy with the KDB—has been developed to provide moderate reductions in intraocular pressure and/or medication burden in eyes with therapeutic needs that may not warrant the risks associated with more traditional procedures such as trabeculectomy and tube-shunt implantation. This review's goal is to synthesize the existing literature into a compendium of excisional goniotomy's indications, technique, efficacy and safety outcomes, and optimal place in glaucoma management.

Review results

Excisional goniotomy with the KDB effectively lowers IOP and reduces the medication burden in eyes with POAG and other forms of glaucoma across the spectrum of both baseline IOP and disease severity. The procedure exhibits a safety profile that is on par with other angle-based surgical interventions and enhanced safety compared to filtration procedures. It can be performed by comprehensive ophthalmologists as well as glaucoma specialists. This procedure as a standalone operation delivers IOP reductions consistent with filtration surgery, and in combination with cataract surgery delivers both IOP and medication reductions at least as great as other minimally invasive procedures.

Conclusion

Given the broad base of evidence supporting its use in a wide variety of clinical scenarios, excisional goniotomy with the KDB can play a meaningful role in the achievement of patient-specific glaucoma therapy goals.

Clinical significance

These aggregate findings support the efficacy and safety of excisional goniotomy with the KDB and clarify the patient profiles best suited for this procedure.

How to cite this article

Dorairaj S, Radcliffe NM, Grover DS, et al. A Review of Excisional Goniotomy Performed with the Kahook Dual Blade for Glaucoma Management. J Curr Glaucoma Pract 2022;16(1):59–64.

Microinvasive glaucoma surgery: a review and classification of implant-dependent procedures and techniques

The aim of this article is to discuss how physiology and anatomical background affect the effectiveness of implant‐dependent microinvasive glaucoma surgery (MIGS). First, we provide a micro view of aqueous outflow and tissue behaviour. Second, we review studies exploring the mechanisms of the pressure‐lowering effect of MIGS, as well as tissue behaviour during aqueous flow and tissue motion. We also describe and classify microinvasive surgical procedures and the most important types of implants, as well as their mechanisms of action, implantation techniques and efficacy. Further, we summarize the indications and surgical results presented in recent studies, providing an evidence‐based update on novel and emerging MIGS techniques for the treatment of open‐angle glaucoma. These data can help surgeons to personalize the management of glaucoma and to choose the best MIGS option for individual glaucoma patients.

Reduction in trabecular meshwork stem cell content in donor eyes with primary open angle glaucoma

We previously identified and characterized human trabecular meshwork stem cells (TMSCs) based on high expression of ABCG2/p75 positivity and high nucleus to cytoplasmic ratio. These TMSCs expressing high ABCG2 and p75 were located to the insert region of the human TM. Additionally, we demonstrated an age-related reduction in the TMSC content which was significantly associated with TM cell loss. In continuation, this study was aimed to determine the TMSC content in glaucomatous donor eyes wherein a drastic reduction in TM cellularity has already been reported. Anterior segments from known glaucomatous (n = 6) and age-matched normal (n = 8) donors were dissected into four quadrants. A minimum of three sections from each quadrant were used for histopathological analysis as well as immunostaining. Analysis of hematoxylin and eosin-stained sections from glaucomatous tissues revealed a decrease in total TM cellularity, thickening of trabecular beams, fusion of trabeculae, absence of patent Schlemm's canal compared to age-matched controls. In addition, the TM thickness at various positions of the meshwork and the coronal as well as the meridional diameters of the Schlemm's canal were observed to be significantly reduced in glaucomatous eyes. Further, sections from both the groups were immunostained for universal stem cell marker ABCG2 and neural crest derived stem cell marker p75. The images were acquired using Leica SP8 confocal microscope. Quantification of total TM cellularity based on nuclear counterstain (mean ± SD) using ImageJ identified 69.33 ± 12.77 cells/section in control eyes. In glaucomatous donors, the TM cellularity was found to be reduced significantly to 41.83 ± 9.0 (p = 0.0007). In addition, a reduction in the percentage of TMSCs (cells with high ABCG2 expression and p75 positivity) was evident in glaucomatous donors (0.14 ± 0.17%) compared to age-matched controls (4.73 ± 5.46%) (p = 0.064). Thus, the present study confirmed the significant decline in TM cellularity and a reducing trend in the TMSC content, though this reduction was non-significant in glaucomatous donor eyes. Further studies are essential to elucidate the role of TMSCs in the pathogenesis of primary open angle glaucoma.

Disease-related and age-related changes of anterior chamber angle structures in patients with primary congenital glaucoma: An in vivo high-frequency ultrasound biomicroscopy-based study

OBJECTIVES

To provide in vivo measurements of anterior chamber angle structures and their relationship with age as evaluated by high-frequency ultrasound biomicroscopy (UBM) in patients with primary congenital glaucoma (PCG).

METHODS

High-frequency UBM was done for 51 PCG eyes from 40 patients (aged from 3 to 96 months) and 11 unaffected contralateral eyes. Parameters, including the proportion of observable abnormal tissue membrane and Schlemm's canal, the largest cross-sectional area (CSA) of Schlemm's canal (SC), SC meridional diameter, trabecular-iris angle (TIA), trabecular meshwork (TM) thickness, iris thickness, ciliary process length, and corneal limbus thickness were compared between the two groups and their relationship with age was explored in PCG eyes.

RESULTS

Abnormal tissue membrane was detected in 27.5% of PCG eyes and none in unaffected eyes. SC was observed in 73.1% of PGC eyes compared to 100% in unaffected eyes (P<0.001). The largest CSA of SC, SC meridional diameter, iris thickness, and corneal limbus thickness were all significantly smaller in PCG eyes compared to unaffected eyes (all P<0.05). TIA and ciliary process length in unaffected eyes were smaller than PCG eyes (both P<0.05). The largest CSA of SC, TM thickness, iris thickness, and ciliary process length were all significantly correlated to age in PCG eyes (P<0.05).

CONCLUSIONS

The anatomical information evaluated by high-frequency UBM may provide glaucoma specialists a useful tool to aid in understanding the dysgenesis and changes with age of anterior chamber angle in PCG.

An injectable peptide hydrogel for reconstruction of the human trabecular meshwork

Glaucoma is a leading cause of irreversible blindness worldwide. Current treatments of glaucoma involve lowering the IOP by means of decreasing aqueous humor production or increasing non-trabecular aqueous humor outflow with the help of IOP-lowering eye drops, nanotechnology enabled glaucoma drainage implants, and trabeculectomy. However, there is currently no effective and permanent cure for this disease. In order to investigate new therapeutic strategies, three dimensional (3D) biomimetic trabecular meshwork (TM) models are in demand. Therefore, we adapted MAX8B, a peptide hydrogel system to bioengineer a 3D trabecular meshwork scaffold. We assessed mechanical and bio-instructive properties of this engineered tissue matrix by using rheological analysis, 3D cell culture and imaging techniques. The scaffold material exhibited shear-thinning ability and biocompatibility for proper hTM growth and proliferation indicating a potential utilization as an injectable implant. Additionally, by using a perfusion system, MAX8B scaffold was tested as an in vitro platform for investigating the effect of Dexamethasone (Dex) on trabecular meshwork outflow facility. The physiological response of hTM cells within the scaffold to Dex treatment clearly supported the effectiveness of this 3D model as a drug-testing platform, which can accelerate discovery of new therapeutic targets for glaucoma. STATEMENT OF SIGNIFICANCE: Artificial 3D-TM (3-dimentional Trabecular Meshwork) developed here with hTM (human TM) cells seeded on peptide-hydrogel scaffolds exhibits the mechanical strength and physiological properties mimicking the native TM tissue. Besides serving a novel and effective 3D-TM model, the MAX8B hydrogel could potentially function as an injectable trabecular meshwork implant.

Optical sectioning and high resolution visualization of trabecular meshwork using Bessel beam assisted light sheet fluorescence microscopy

Glaucoma, one of the leading causes of blindness, is an eye disease caused by irregularities in the ocular aqueous outflow system causing an elevated intraocular pressure. High resolution imaging of the aqueous outflow system comprising trabecular meshwork is immensely valuable to vision analysts and clinicians in comprehending the disease state for the efficacious analysis and treatment of glaucoma. Currently available ocular imaging devices are unable to deliver high resolution images for the visualization of the trabecular meshwork. A method to obtain high resolution (sub-micrometer) images of the trabecular meshwork using Bessel-Gauss beam scanned light sheet fluorescence microscopy is presented and the optical sectioning capability of this technique to obtain three-dimensional volumetric images of the trabecular meshwork of an intact eye without any physical dissection is demonstrated. Figure: Three-dimensional visualization of trabecular meshwork of porcine eye.

Schlemm's canal measured by optical coherence tomography and correlation study in a healthy Caucasian child population

PURPOSE

To measure the Schlemm's canal (SC) in vivo by Fourier-domain optical coherence tomography (FD-OCT) in a Caucasian paediatric population.

METHODS

Participants of this cross-sectional study were 290 healthy children. In the right eye of each child, SC cross-sectional diameter and area measurements were made with the FD-OCT instrument RTVue^® (Optovue Inc, Fremont, CA, USA) in the nasal and temporal quadrants. These SC variables were then assessed for correlation with the factors age, gender, refractive error, anterior chamber angle and trabecular meshwork (TM) metrics. Finally, the reproducibility of the SC measurements was assessed in 30 of the participants.

RESULTS

Mean participant age was 10.7 ± 3.4 years (range 3-18). SC diameters could be measured in both quadrants in 70.6% and 70.4% of subjects, respectively. Mean SC diameters were similar (p = 0.125) for the temporal and nasal quadrants: 266.7 ± 84.1 μm (range 131-509) and 273.2 ± 77.3 μm (range 124-486), respectively. Mean SC areas were also similar (p = 0.167) for the two quadrants: 9975 ± 3514 μm² (range 4000-23 000) versus 9688 ± 3297 μm² (range 3000-24 000). No differences were detected in SC measurements according to gender, refractive error or angle and TM measurements (R ≤ 0.116; p ≥ 0.125). The exception was age which was directly correlated with SC size (p ≤ 0.041). The reproducibility of the SC measurements was excellent (intraclass correlation coefficients ≥0.936).

CONCLUSION

FD-OCT allows the identification of the SC in children. Our data indicate an increase in SC size produced with age.

Development of a Spherical Model with a 3D Microchannel: An Application to Glaucoma Surgery

Three-dimensional (3D) microfluidic channels, which simulate human tissues such as blood vessels, are useful in surgical simulator models for evaluating surgical devices and training novice surgeons. However, animal models and current artificial models do not sufficiently mimic the anatomical and mechanical properties of human tissues. Therefore, we established a novel fabrication method to fabricate an eye model for use as a surgical simulator. For the glaucoma surgery task, the eye model consists of a sclera with a clear cornea; a 3D microchannel with a width of 200–500 µm, representing the Schlemm’s canal (SC); and a thin membrane with a thickness of 40–132 µm, representing the trabecular meshwork (TM). The sclera model with a clear cornea and SC was fabricated by 3D molding. Blow molding was used to fabricate the TM to cover the inner surface of the sclera part. Soft materials with controllable mechanical behaviors were used to fabricate the sclera and TM parts to mimic the mechanical properties of human tissues. Additionally, to simulate the surgery with constraints similar to those in a real operation, the eye model was installed on a skull platform. Therefore, in this paper, we propose an integration method for fabricating an eye model that has a 3D microchannel representing the SC and a membrane representing the TM, to develop a glaucoma model for training novice surgeons.

CO2 laser-assisted sclerectomy surgery compared with trabeculectomy in primary open-angle glaucoma and exfoliative glaucoma. A 1-year follow-up

PURPOSE

To report on the efficacy and safety of CO₂ laser-assisted sclerectomy surgery (CLASS) compared with trabeculectomy in primary open-angle glaucoma and exfoliative glaucoma.

METHODS

One hundred and thirty-one patients underwent CLASS (66 patients) or trabeculectomy (65 patients) and were followed up for 12 months. 'Complete success' was defined as intraocular pressure (IOP) between 10 and 18 mmHg and reduced by at least 30% from the baseline without medications, while 'qualified success' was compliant with the above criteria with or without the medications.

RESULTS

Comparing CLASS with trabeculectomy at 1 year, the mean IOP reduction rate was 32.6 ± 10.8% versus 40.6 ± 15.9% (p < 0.001) and the average use of medications was 1.4 ± 1.4 versus 0.7 ± 1.1 (p < 0.05). At 12 months, the complete success rate was 35% for CLASS versus 60% for trabeculectomy (p < 0.01), while the qualified success rate was 74% versus 75%, respectively, with no significant difference in qualified success rate between the groups at any time-point (p > 0.05). Compared with CLASS, patients after trabeculectomy developed a higher rate of early complications (9.1% versus 29.2%, p = 0.004), higher endothelial cell density (ECD) loss (1.4 ± 1.4% versus 6.5 ± 4.8%, p < 0.001), higher astigmatism (0.0 ± 0.1 versus 0.1 ± 0.2, p < 0.001) and significant visual acuity deterioration (0.1 ± 0.1; range 0-2 lines versus 0.4 ± 0.6; range 0-3 lines, p = 0.016).

CONCLUSION

Although CLASS shows a less potent hypotensive effect, it is similar to trabeculectomy in the qualified success rate and offers the reduction in medications up to 12 months. With a more attractive complications profile, CLASS may be an alternative to trabeculectomy, especially at the earlier glaucoma stage and in patients with a low ECD.

Nonpenetrating Deep Sclerectomy: A 6-Year Retrospective Study

Purpose

Nonpenetrating trabeculectomy, also called nonpenetrating deep sclerectomy (NPDS), is a filtering surgery where the internal wall of Schlemm's canal is excised, allowing sub-conjunctival filtration without actually entering the anterior chamber. This technique was developed to minimize the complications of trabeculectomy. The authors investigated its safety and efficacy in a retrospective noncomparative study.

METHODS

A total of 258 eyes (179 patients, mean age 61.4±11.56 years) with uncontrolled open angle glaucoma with prior medical therapy were treated. NPDS with a biocompatible collagen device (157 eyes) sutured to deep scleral bed or with the use of a 5-fluorouracil sponge (90 eyes) were analyzed. The main outcome measure was postoperative intraocular pressure (IOP) with an average follow-up of 54.4±17.07 months (range 1–85). Efficacy was determined 1 month, 3 months, and every 6 months after the procedure for 6 years.

Results

Mean preoperative IOP was 24.47±5.92 mmHg. Mean postoperative IOP was 14.44±5.31 mmHg (average lowering of the IOP was 38.94±23.81%) at 1 month, 15.16±4.57 mmHg (35.73±21.35%) at 3 months, 15.87±4.24 mmHg (32.45 ±20.52%) at 6 months, 16.32±4.53 mmHg (29.96±23.69%) at 12 months, 17.12±4.45 mmHg (26.51±23.93%) at 18 months, 16.77±4.44 mmHg (28.18±21.73%) at 24 months, 16.43±4.15 mmHg (28.89±23.69%) at 30 months, 16.34±4.12 mmHg (30.05±21.61%) at 36 months, 16.16±4.01 mmHg (30.06±22.55%) at 42 months, 15.71±3.74 mmHg (32.49±19.08%) at 48 months, 15.61±3.48 mmHg (31.26±21.01%) after 5 years, and 15.81 ±3.79 mmHg (33.73±20.9%) after 6 years. YAG goniopuncture was performed in 47.3% of cases with a mean follow-up of 12±13 months. These goniopunctures were effective in lowering IOP after a long-term follow-up (24 months). Additional 5-fluorouracil injections were used in 7% of cases. Visual field (Octopus or Humphrey mean defect and corrected loss variance or loss variance) was not modified (p<0.01). Number of preoperative glaucoma medications was 2.01±0.58 and number of postoperative glaucoma medications was 0.85±0.92. Complications were peroperative microperforations in 27 eyes (10.5%), shallow anterior chamber in 2 eyes, hyphema in 2 eyes (0.8%), cataract in 5 eyes (2%), and dellen in 1 eye (0.4%). No cases of endophthalmitis or choroidal detachment were found. After surgery, 23 eyes (8.9%) required a new filtering surgical procedure, and diode laser cyclophotocoagulation was necessary in 2 eyes (0.8%). The probability success rate, defined as an IOP lower than 21 mmHg, was 66.46% (Kaplan Meier) at 60 months off all glaucoma medications and 80.32% with medical or new surgical treatment.

CONCLUSIONS

NPDS appears to be an effective and safe filtering procedure for lowering IOP and could be an alternative to trabeculectomy in open angle glaucoma with the advantage of having fewer complications.

Stiffness characterization of anisotropic trabecular meshwork

Elevation of intraocular pressure has been correlated to changes in stiffness of trabecular meshwork (TM) in glaucomatous eyes although mechanical properties of the TM remain to be quantitatively determined. Data in the literature suggest that the TM cannot be considered mechanically as a uniform layer of isotropic elastic material, because the value of its Young's modulus depends on the methods of measurements and can vary up to five orders of magnitude. To this end, we proposed a new theoretical framework for mechanical analysis of the TM, in which the inner wall of Schlemm's canal and the juxtacanalicular tissue in the TM were treated as a uniform layer of isotropic elastic material, and the rest of the TM, i.e., the uveal and corneoscleral meshworks, were modeled as a uniform layer of transversely isotropic material. Using the model, we demonstrated that the large discrepancy in the apparent Young's modulus reported in the literature could be caused by the anisotropy of the meshwork that was significantly stiffer in the longitudinal direction than in the transverse direction. The theoretical framework could be used to integrate existing data of the stiffness, investigate anisotropic behaviors of the tissues, and develop new methods to measure mechanical properties of the TM.

Ultrasound biomicroscopy measurement of Schlemm's canal in pediatric patients with and without glaucoma

PURPOSE

To compare the diameter of Schlemm's canal in children with and without congenital glaucoma as measured in vivo by means of ultrasound biomicroscopy.

METHODS

In this prospective single-center study of pediatric subjects (<18 years of age) the diameter of Schlemm's canal in nonglaucomatous and glaucomatous eyes was compared. An 80 MHz iUltrasound probe (iScience Interventional Inc, Menlo Park, CA) placed near the limbus was used to identify and measure the canal's diameter with special attention to the anterior segment anatomy (especially in subjects with congenital glaucoma).

RESULTS

A total of 20 subjects were included; mean age of subjects without glaucoma was 6.6 ± 6.65 years; of those with glaucoma, 9.4 ± 11.80 months. The mean canal diameter in nonglaucomatous eyes was 142 ± 33.2 μm (range, 90-196 μm); in glaucomatous eyes, 64.9 ± 10.90 μm (P = 0.007). Schlemm's canal could not be identified in 50% of patients with congenital glaucoma. There was a trend toward smaller canal diameter in subjects with no glaucoma <2 years old. Mean canal diameter in nonglaucomatous eyes was 103 ± 8 μm (range, 90-115 μm) in subjects <2 years of age and 161 ± 20 μm (range, 110-196 μm) in subjects >2 years of age (P = 0.0012).

CONCLUSIONS

In our pediatric study cohort the diameter of Schlemm's canal varied by age and presence of glaucoma.

Schlemm's Canal and Trabecular Meshwork in Eyes with Primary Open Angle Glaucoma: A Comparative Study Using High-Frequency Ultrasound Biomicroscopy

We investigated in vivo changes in Schlemm’s canal and the trabecular meshwork in eyes with primary open angle glaucoma (POAG). Relationships between Schlemm’s canal diameter, trabecular meshwork thickness, and intraocular pressure (IOP) were examined. Forty POAG patients and 40 normal individuals underwent 80-MHz Ultrasound Biomicroscopy examinations. The Schlemm’s canal and trabecular meshwork were imaged in superior, inferior, nasal and temporal regions. Normal individuals had an observable Schlemm’s canal in 80.3% of sections, a meridional canal diameter of 233.0±34.5 μm, a coronal diameter of 44.5±12.6 μm and a trabecular meshwork thickness of 103.9±11.1 μm, in POAG patients, Schlemm’s canal was observable in 53.1% of sections, a meridional canal diameter of 195.6±31.3 μm, a coronal diameter of 35.7±8.0 μm, and a trabecular meshwork thickness of 88.3±13.2 μm, which significantly differed from normal (both p <0.001). Coronal canal diameter (r = -0.623, p < 0.001) and trabecular meshwork thickness (r = -0.663, p < 0.001) were negatively correlated with IOP, but meridional canal diameter was not (r = -0.160, p = 0.156). Schlemm’s canal was observable in 50.5% and 56.6% of POAG patients with normal (<21 mmHg) and elevated (>21 mmHg) IOP, respectively (χ = 1.159, p = 0.282). Coronal canal diameter was significantly lower in the elevated IOP group (32.6±4.9 μm) than in the normal IOP group (35.7±8.0 μm, p < 0.001). This was also true of trabecular meshwork thickness (81.9±10.0 μm vs. 97.1±12.0 μm, p < 0.001). In conclusion, eyes with POAG had fewer sections with an observable Schlemm’s canal. Canal diameter and trabecular meshwork thickness were also lower than normal in POAG patients. Schlemm’s canal coronal diameter and trabecular meshwork thickness were negatively correlated with IOP.

Topical trans-resveratrol ameliorates steroid-induced anterior and posterior segment changes in rats

Steroid-induced hypertension and glaucoma is associated with increased extracellular meshwork (ECM) deposition in trabecular meshwork (TM). Previous studies have shown that single drop application of trans-resveratrol lowers IOP in steroid-induced ocular hypertensive (SIOH) rats. This IOP lowering is attributed to activation of adenosine A1 receptors, which may lead to increased matrix metalloproteinase (MMP)-2 activity. This study evaluated the effect of repeated topical application of trans-resveratrol for 21 days in SIOH animals on IOP, changes in MMP-2 level in aqueous humor, trabecular meshwork and retinal morphology and retinal redox status. We observed that treatment with trans-resveratrol results in significant and sustained IOP reduction in SIOH rats. This IOP reduction is associated with significantly higher aqueous humor total MMP-2 level; significantly reduced TM thickness and increased number of TM cells. Treatment with trans-resveratrol also significantly increased ganglion cell layer (GCL) thickness, the linear cell density in the GCL and inner retina thickness; and significantly reduced retinal oxidative stress compared to the SIOH vehicle-treated group. In conclusion, repeated dose topical application of trans-resveratrol produces sustained IOP lowering effect, which is associated with increased level of aqueous humor MMP-2, normalization of TM and retinal morphology and restoration of retinal redox status.

Anterior and posterior segment changes in rat eyes with chronic steroid administration and their responsiveness to antiglaucoma drugs

Steroid-induced ocular hypertension (SIOH) is associated with topical and systemic use of steroids. However, SIOH-associated anterior and posterior segment morphological changes in rats have not been described widely. Here we describe the pattern of intraocular pressure (IOP) changes, quantitative assessment of trabecular meshwork (TM) and retinal morphological changes and changes in retinal redox status in response to chronic dexamethasone treatment in rats. We also evaluated the responsiveness of steroid-pretreated rat eyes to 5 different classes of antiglaucoma drugs that act by different mechanisms. Up to 80% of dexamethasone treated animals achieved significant and sustained IOP elevation. TM thickness was significantly increased and number of TM cells was significantly reduced in SIOH rats compared to the vehicle-treated rats. Quantitative assessment of retinal morphology showed significantly reduced thickness of ganglion cell layer (GCL) and inner retina (IR) in SIOH rats compared to vehicle-treated rats. Estimation of retinal antioxidants including catalase, superoxide dismutase and glutathione showed significantly increased retinal oxidative stress in SIOH animals. Furthermore, steroid-treated eyes showed significant IOP lowering in response to treatment with 5 different drug classes. This indicated the ability of SIOH eyes to respond to drugs acting by different mechanisms. In conclusion, SIOH was associated with significant morphological changes in TM and retina and retinal redox status. Additionally, SIOH eyes also showed IOP lowering in response to drugs that act by different mechanisms of action. Hence, SIOH rats appear to be an inexpensive and noninvasive model for studying the experimental antiglaucoma drugs for IOP lowering and neuroprotective effects.

Walking through trabecular meshwork biology: Toward engineering design of outflow physiology

According to the World Health Organization, glaucoma remains the second leading cause of blindness in the world. Glaucoma belongs to a group of optic neuropathies that is characterized by chronic degeneration of the optic nerve along with its supporting glia and vasculature. Despite significant advances in the field, there is no available cure for glaucoma. The trabecular meshwork has been implicated as the primary site for regulation of intraocular pressure, the only known modifiable factor in glaucoma development. In this review, we describe the current models for glaucoma studies, primary culture, anterior eye segments, and animal studies and their limitations. These models, especially anterior eye segments and animal tissues, often require careful interpretation given the inter-species variation and are cumbersome and expensive. The lack of an available in vitro 3D model to study trabecular meshwork cells and detailed mechanisms of their regulation of intraocular pressure has limited progress in the field of glaucoma research. In this paper, we review the current status of knowledge of the trabecular meshwork and how the current advances in tissue engineering techniques might be applied in an effort to engineer a synthetic trabecular meshwork as a 3D in vitro model to further advance glaucoma research. In addition, we describe strategies for selection and design of biomaterials for scaffold fabrication as well as extracellular matrix components to mimic and support the trabecular architecture. We also discuss possible uses for a bioengineered trabecular meshwork for both developing a fundamental understanding of trabecular meshwork biology as well as high-throughput screening of glaucoma drugs.

Current surgical options for the management of pediatric glaucoma

Currently, there are numerous choices for the treatment of pediatric glaucoma depending on the type of glaucoma, the age of the patient, and other particularities of the condition discussed in this review. Traditionally, goniotomy and trabeculotomy ab externo have been the preferred choices of treatment for congenital glaucoma, and a variety of adult procedures adapted to children have been utilized for other types of pediatric glaucoma with variable results and complications. More recently, seton implantations of different types have become more popular to use in children, and newer techniques have become available including visualized cannulation and opening of Schlemm's canal, deep sclerectomy, trabectome, and milder more directed cyclodestructive procedures such as endolaser and transcleral diode laser cyclophotocoagulation. This paper reviews the different surgical techniques currently available, their indications, results, and most common complications to allow the surgeon treating these conditions to make a more informed choice in each particular case. Although the outcome of surgical treatment in pediatric glaucoma has improved significantly, its treatment remains challenging.

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.

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.

Schlemm??s Canal Endothelia, Lymphatic, or Blood Vasculature?

In the human eye, the final barrier for aqueous humor to cross before returning to systemic circulation is the inner wall of Schlemm's canal. Unfortunately, the specific contribution of the inner wall to total outflow resistance in the conventional pathway is unknown in both normal and glaucomatous eyes. To better understand inner wall physiology, we contrasted it with 2 specialized continuous endothelia, initial lymphatic, and blood capillary endothelia. Specifically, we compare their developmental origin, morphology, junctional complexes, microenvironment, and physiologic responses to different biomechanical factors. Our evaluation concludes that the inner wall of Schlemm's canal is unique, sharing extraordinary characteristics with both types of specialized endothelia in addition to having distinctive features of its own.

Influence of deep scleral flap size on intraocular pressure after deep sclerectomy

PURPOSE

To study the effect of several morphometric characteristics of the deep scleral flap on intraocular pressure (IOP) control after deep sclerectomy.

METHODS

The authors conducted a nonrandomized prospective study of 56 eyes of 51 patients who underwent deep sclerectomy alone or combined with phacoemulsification. A reticulated hyaluronic acid implant was used in all cases. The surface, volume, and weight of the dissected deep scleral flap were measured and recorded. The correlation between these parameters and the postoperative IOP was evaluated at 6 and 12 months postoperatively.

RESULTS

Forty-nine eyes (87.50%) achieved an IOP of 21 mmHg or less without treatment, and the need for medication was decreased significantly (p<0.001) at 12 months postoperatively. The authors found a significant inverse correlation between the mean postoperative IOP at 6 months and the surface, volume, and weight of the deep scleral flap, but not at 12 months postoperatively.

CONCLUSIONS

Greater weight, surface area, and volume of the deep scleral flap dissected during deep sclerectomy achieve significantly lower postoperative IOPs in the early postoperative period.

Nonpenetrating glaucoma surgery: a critical evaluation

PURPOSE OF REVIEW

Nonpenetrating glaucoma surgery is popular in a number of countries because of its perceived superior safety profile to mitomycin-C trabeculectomy. This article critically evaluates recently published literature relating to nonpenetrating glaucoma surgery.

RECENT FINDINGS

Recent modifications in nonpenetrating glaucoma surgery, including the use of implants, augmentation with antiproliferatives, and use of laser goniopuncture, appear to result in improved intraocular pressure control. Comparative studies suggest a better safety profile with nonpenetrating glaucoma surgery but higher long-term intraocular pressure than after trabeculectomy. Despite this perception, a difference in intraocular pressure control between mitomycin-C trabeculectomy and nonpenetrating glaucoma surgery, when the most recent modification has been incorporated, has not been demonstrated conclusively in randomized trials conducted over sufficiently long periods to be clinically important.

SUMMARY

Nonpenetrating glaucoma surgery continues to evolve. Intraocular pressure-lowering efficacy seems to have improved with recent modifications in technique but the degree and longevity of intraocular pressure-lowering in comparison with trabeculectomy are still uncertain.

Seven-year follow-up of combined cataract extraction and viscocanalostomy

PURPOSE

To investigate the long-term success and complications of phacoemulsification combined with viscocanalostomy (phacoviscocanalostomy) in eyes with coexisting cataract and medically uncontrolled glaucoma.

SETTING

Department of Ophthalmology, Warrington Hospital, Warrington, United Kingdom.

METHODS

A prospective nonrandomized study evaluated 165 consecutive eyes (114 patients) that had phacoviscocanalostomy. The main outcome measures were intraocular pressure (IOP), visual acuity, requirement for topical antiglaucoma medication, and the presence or absence of drainage blebs or bleb complications.

RESULTS

The mean follow-up was 38.7 months +/- 19.3 (SD) (range 12 to 90 months). There was a statistically significant decrease in IOP, from 24.1 +/- 5.1 mm Hg preoperatively to 13.8 +/- 8.1 mm Hg 1 day after surgery (P<.001), 16.0 +/- 4.1 mm Hg at 5 years (P<.001), and at all evaluations to the last follow-up. The mean number of medications per eye decreased significantly from 2.5 +/- 0.9 before surgery to 0.1 +/- 0.5 at last follow-up (P<.001). At the final follow-up, IOP was reduced by 33.2% (16.2 mm Hg versus 24.1 mm Hg). Complete success, defined as an IOP reduction of more than 30% from preoperative level without medications, was achieved in 48.5% of eyes, with 42% of eyes having an IOP of less than 16 mm Hg. The percentage fall in IOP was linearly related to the preoperative IOP level (P<.001). No eye developed a trabeculectomy-type bleb, and there were no bleb-related complications.

CONCLUSIONS

Phacoviscocanalostomy was safe and effective for the management of eyes with coexisting cataract and medically uncontrolled glaucoma. It provided a stable and sustained reduction in IOP with a minimum requirement for topical medication.

Femtosecond laser photodisruption of human trabecular meshwork: an in vitro study

The goal of this in vitro study was to test the feasibility of using femtosecond (fsec) laser pulses to fistulize the human trabecular meshwork (TM), and to determine the minimum exposure time and energy dosage needed to create an ablation channel. Corneo-scleral rims were obtained from tissue used for penetrating keratoplasty. Four millimeter tissue strips hydrated in Optisol-GS were used to create partial thickness fistulas in the human TM by focusing a Ti:Sapphire laser beam (45 fsec, 1 kHz, 800 nm) with various pulse energies (7.2 and 14.4 microJ) and exposure times (0.25, 0.5, 1, and 2 sec) on the inner surface of the TM. Two-photon images of the lesions were obtained with a multiphoton microscope, using an ultrafast Ti:Sapphire light source. In addition, sections of fixed tissue were examined by light microscopy. Diameters and lengths of the lesions were determined from the hematoxylin and eosin (H&E) stained sections, and the collagen structure surrounding the lesion was evaluated from the two-photon images. All selected time points (except for 0.25 sec) and energies achieved the desired photodisruption of the TM. Incisions created with 0.5 sec/14.4 microJ irradiation appeared to be the most suitable because they were able to achieve consistent full thickness trabecular ablation. Incisions created at 1 sec /14.4 microJ/pulse and 2 sec/14.4 microJ/pulse were deeper than those at shorter time points with the same pulse energy. Longer exposure times and higher pulse energies were usually more variable and associated with deeper and larger incisions and slight collateral damage. Our results indicate that, with appropriate exposure time and pulse energy, fsec photodisruption can be employed to create lesions in the human TM without damaging the surrounding tissues. This study demonstrates that fsec laser treatments may have future potential for the surgical treatment of glaucoma.

Primary viscocanalostomy versus trabeculectomy for primary open-angle glaucoma

PURPOSE

To compare the efficacy and safety of viscocanalostomy and trabeculectomy in patients with primary open-angle glaucoma (POAG).

SETTING

Department of Ophthalmology, Ankara Education and Research Hospital, Ankara, Turkey.

METHODS

In this prospective randomized trial, 50 eyes of 50 patients with medically uncontrolled POAG were randomized to have a trabeculectomy (25 eyes) or a viscocanalostomy (25 eyes). Visual acuity, intraocular pressure (IOP), and slitlamp examinations were performed before surgery and 1 day, 1 week, 1, 3, and 6 months, and 1, 2, and 3 years postoperatively.

RESULTS

At 3 years, the mean IOP was 16.0 mmHg +/- 7.07 (SD) in the trabeculectomy group and 17.8 +/- 4.6 mmHg in the viscocanalostomy group (P=.694). Complete success (IOP 6 to 21 mm Hg without medication) was achieved in 66.2% of eyes at 6 months and 55.1% at 3 years in the trabeculectomy group and in 52.9% and 35.3%, respectively, in the viscocanalostomy group (P>.05). Qualified success (IOP 6 to 21 mmHg with medication) was achieved in 95.8% of eyes at 6 months and 79.2% at 3 years in the trabeculectomy group and in 90.7% and 73.9%, respectively, in the viscocanalostomy group (P>.05). Postoperative hypotony and cataract formation occurred more frequently in the trabeculectomy group than in the viscocanalostomy group (P=.002).

CONCLUSIONS

Primary trabeculectomy lowered IOP more than viscocanalostomy in POAG patients. However, the complication rate was lower in the viscocanalostomy group.

Viscocanalostomy and deep sclerectomy for the surgical treatment of glaucoma: a longterm follow-up

PURPOSE

To study the outcome of viscocanalostomy (VC) and deep sclerectomy (DS) for the surgical management of medically uncontrolled glaucoma.

PATIENTS AND METHODS

A non-randomized, prospective study of all consecutive non-penetrating glaucoma filtering procedures was carried out in two centres. In the first centre, one surgeon (MSW) performed VC in 105 eyes (27 VC and 78 phaco VC). In the second centre, one surgeon (PKW) performed DS in 87 eyes (52 DS and 35 phaco DS).

RESULTS

The mean follow-up was 36 months (range 9-60 months). At final follow-up the complete success rate (intraocular pressure < or = 21 Hg without medication) was 92.6% for VC eyes, 96% for phaco VC eyes, 77% for DS eyes and 94% for phaco DS eyes. Kaplan-Meier survival analysis for complete success showed no significant difference between DS and VC nor between phaco VC and phaco DS (p > 0.05). By 36 months postoperatively, mean IOP was 16.8 mmHg (SD 3) in VC eyes, 16.6 mmHg (SD 3.1) in phaco VC eyes, 16.7 mmHg (SD 5.7) in DS eyes and 15 mmHg (SD 3.2) in phaco DS eyes. Postoperative Nd:YAG laser goniopuncture was necessary in 10 eyes in the DS group. Large or cystic drainage blebs occurred only in the DS eyes.

CONCLUSIONS

Viscocanalostomy and DS are effective and safe methods of achieving sustained IOP reduction in glaucomatous eyes and both techniques can be successfully combined with cataract extraction.

A prospective randomized trial of viscocanalostomy versus trabeculectomy in open-angle glaucoma: a 1-year follow-up study

PURPOSE

To assess the intraocular pressure-lowering efficacy and the postoperative complication profile of viscocanalostomy versus trabeculectomy.

PATIENTS AND METHODS

Sixty eyes of 60 patients with medically uncontrolled open-angle glaucoma were randomized either to the viscocanalostomy or to the trabeculectomy group of the trial. Viscocanalostomy was performed according to Stegmann's technique using high-molecular-weight sodium hyaluronate to fill the ostia of the Schlemm canal. For trabeculectomy, a modified Cairns-trabeculectomy was performed. Examinations were performed before surgery and postoperatively daily for 1 week. Follow-up visits were scheduled 1, 6, and 12 months after surgery.

RESULTS

The mean (SD) preoperative intraocular pressure was 27.1 (7.1) mm Hg for all patients enrolled. One day after surgery, mean (SD) intraocular pressure was 15.9 (5.2) for the trabeculectomy group (P <0.001) and 15.7 (3.6) for the viscocanalostomy group (P <0.001), respectively. The success rate, defined as an intraocular pressure lower than 22 mm Hg without medication, was 56.7% in the trabeculectomy group and 30% in the viscocanalostomy group at 12 months postoperatively (P = 0.041). The number of postoperative complications was lower in the viscocanalostomy group than in the trabeculectomy group.

CONCLUSIONS

In eyes with open-angle glaucoma, viscocanalostomy is less effective in reducing intraocular pressure than standard filtering surgery. However, postoperative complications are more frequent after filtering surgery.

Individual factors influencing trabecular morphology in glaucoma patients undergoing filtration surgery

PURPOSE

Epidemiologic studies have shown that various lifestyle characteristics are statistically associated with the chronic open-angle glaucomas. This study was designed to investigate the influence of individual factors on the light-microscopic morphology of the trabecular meshwork in open-angle glaucomas.

METHODS

Quantitative computer-assisted topographic analysis of the trabecular meshwork was performed in meridional sections of 80 trabeculectomy specimens from patients with primary open-angle (n = 36), exfoliative (n = 30) and pigment-dispersion (n = 14) glaucoma. Measurements included inner wall length of the, central thickness of the trabecular meshwork, and compactness of the Schlemm canal and trabecular meshwork. Morphologic data were correlated with individual patient data including age, duration of the disease, maximum intraocular pressure, cup-disc ratio, refraction, height, weight, body mass index, a simple morbidity index, previous surgery, and number of topical antiglaucomatous medications used.

RESULTS

Inner wall length of the Schlemm canal was significantly lower in eyes with previous filtering surgery (P = 0.03), but not in eyes with a high number of topical medications (P = 0.17). There was a significant tendency for the inner wall length of the Schlemm canal to be shortened in patients where high maximum intraocular pressure was combined with long-term glaucoma (P = 0.027). Body mass index did not differ significantly between patients with primary open-angle, exfoliative, and pigment-dispersion glaucoma and showed no correlation with the quantitative data of the meshwork. The morbidity index correlated well with body mass index (0.0006) and age (P < 0.0001).

CONCLUSION

Contrary to findings of experimental mice studies, we found no indication that glaucoma patients with lower body mass index have a larger lumen of the Schlemm canal than patients with a higher body mass index. Although caution should be used when interpreting data from trabeculectomy studies, there is a certain probability that a history of previous filtering surgery and of a long-term high intraocular pressure will be associated with a shortening of the Schlemm canal.

Risk profile of deep sclerectomy for treatment of refractory congenital glaucomas

OBJECTIVES

To evaluate the effectiveness and risk profile of deep sclerectomy in surgery for refractory congenital glaucoma.

DESIGN

Retrospective non-comparative interventional case series.

PARTICIPANTS AND INTERVENTIONS

Ten eyes of eight consecutive patients underwent deep sclerectomy for refractory congenital glaucoma. The procedure was converted to a trabeculectomy in four eyes and supplemented by a trabeculotomy in two eyes. Six eyes had primary congenital glaucoma, and four eyes had secondary congenital glaucoma. The patients' ages at the time of surgery in our department ranged from 8 months to 14 years. All eyes had a history of previous glaucoma surgery.

MAIN OUTCOME MEASURES

The surgical outcome was assessed in terms of complication rate, intraocular pressure (IOP) change, need for surgical revision, or additional glaucoma medication.

RESULTS

Preoperatively, the mean IOP was 31.9 mmHg (standard deviation [SD], 5.6 mmHg). At first follow-up 1 week after surgery, the mean IOP for all eyes was 12.7 mmHg (SD, 6.8 mmHg). The average reduction of IOP was statistically significant (P < 0.001). In accordance with the success criteria, all eyes were ultimately classified as failures. Average time to failure was 2.1 months (SD, 3.6 months). Specific complications were seen in terms of non-identification of Schlemm's canal (40%), choroidal deroofing (10%), and visible perforation of the trabeculodescemetic membrane (20%). Further complications were hyphema (40%), ocular hypotony (10%), vitreous hemorrhage (10%), and vitreous loss with subsequent retinal detachment (10%).

CONCLUSIONS

Although deep sclerectomy may reduce the IOP in patients with refractory congenital glaucoma, this study indicates a specific risk profile associated with deep sclerectomy in surgery for refractory congenital glaucoma.