Endoscopic surgery in glaucoma management

Endoscopically-controlled intraocular surgery has been evolving rapidly since the introduction of thinner endoprobes with increasing resolving power and higher image quality. Currently, anti-glaucomatous surgery is also beginning to take advantage of this exciting new technology. This article discusses the two main approaches to glaucoma management using microendoscopic techniques-decreasing aqueous humor production by means of laser endoscopic cyclophotocoagulation and increasing outflow facility through endoscopically-controlled selective trabecular surgery. Besides presenting clinical results, emphasis is placed on different surgeons' accounts of intraoperative endoscopic maneuverability and the spectrum of complications that may be attributed to the endoscopic nature of the surgical intervention.     

Photoablative laser-grid trabeculectomy in glaucoma filtering surgery: histology and outflow facility measurements in porcine cadaver eyes

BACKGROUND AND OBJECTIVE: Mid-infrared laser technology opens new perspectives in experimental glaucoma surgery. The aim of the study was to determine the efficacy of grid-laser trabeculectomy to reduce aqueous outflow resistance sufficiently in perfused porcine cadaver eyes. MATERIALS AND METHODS: Twenty-five freshly enucleated porcine cadaver eyes were randomly assigned to either laser-grid trabeculectomy (LGT), conventional trabeculectomy (CT), or control. In all surgical cases a scleral flap was prepared in a standardized manner. In order to penetrate into the anterior chamber a 1 x 2 mm sclerectomy was performed in CT, and 10 transscleral ablation craters were created in LGT. An erbium:YAG laser (2.96 microm) was used for transscleral photoablation. Radiation was delivered in a single 6 mJ-pulse of 200 micros duration by means of an articulated zirconium fluoride optical fiber and a 200 microm quartz fiber-tip. Outflow facility was measured at a constant perfusion pressure. RESULTS: Laser-grid trabeculectomy (LGT) yielded reproducible ablation areas varying between 210-300 microm in diameter, with 90% being full-thickness penetrations. Collateral thermal damage was less than 30 microm. Outflow facility measurements revealed a statistically significant increase (mean +/- SD) from 0.255 +/- 0.096 microL/min/mm Hg in control eyes (n = 9) to 0.772 +/- 0.157 microL/min/mm Hg in the LGT group (n = 9), and 2.957 +/- 0.602 microL/min/mm in the CT group (n = 7). Flattening of the anterior chamber, folding of Descemet's membrane, and iris prolapse were only observed in the CT eyes but not in the GLT group. CONCLUSION: Application of the laser-grid trabeculectomy produces patent transscleral perforation with minimal collateral tissue damage and effects a significant reduction (67%) in outflow resistance without any postoperative hypotony-related complications.     

Radioimmunotherapy with yttrium-90 ibritumomab tiuxetan. Clinical considerations, radiopharmacy, radiation protection, perspectives

90Y-ibritumomab tiuxetan (Zevalin) is currently approved for radioimmunotherapy of patients with relapsed or refractory follicular non-Hodgkin's lymphoma pretreated with rituximab. Future directions are the combined use of 90Y-ibritumomab tiuxetan as part of the initial treatment and as first-line multi-agent therapy of relapsed disease. Current studies investigate patients with other than follicular indolent histologies, e. g. diffuse large cell lymphoma. Labelling of 90Y ibritumomab tiuxetan is a safe procedure, the radiochemical purity is not disturbed by a higher room temperature or by metallic impurity. Quality control is recommended by thin layer chromatography (TLC), strips >15 cm are favourable. TLC cannot distinguish between the correctly radiolabelled antibodies and radiocolloid impurity. If necessary, additional HPLC should be performed. Radiocolloid impurities are absorbed to the solid phase and do not reach the eluate. If the radiochemical purity test is insufficient (<95%), the additional cleaning using EconoPac 10 DG columns (Biorad, Hercules, CA, USA) is a reliable procedure to reduce the percentage of free radionuclide. However, this procedure is not part of the approval.     

Stability of radioactive colloids for radiation synovectomy: influence of X-ray contrast agents, anaesthetics and glucocorticoids in vitro

AIM: This in-vitro study investigated the influence of the contrast agents iothalamate (Conray) and special preparations of iotrolan (Isovist) and iopromide (Ultravist) without ethylenediaminetetraacetic acid (EDTA), the anaesthetic Scandicain and the glucocorticoid triamcinolone on the stability of 90Y-, 169Er- and 186Re-radiocolloids used for radiation synovectomy. METHODS: Vials of 1 ml of synovial fluid and 0.02 ml of radiocolloid suspension (0.56-3.6 MBq) were mixed with 0.06, 0.6 and 1.0 ml of each contrast agent. In an additional series, 0.1 ml of Scandicain and 0.1 ml of triamcinolone were tested. Thin layer chromatography and ultrafiltration/centrifugation were performed between 1 h and 15 days after incubation with negative and positive controls. RESULTS: Within 24 h, 0.6 and 1.0 ml of Conray had mobilized 5-20% of the 90Y and 169Er out of the colloids. No interference between 186Re-colloids and Conray was visible before the ninth day after incubation. Iotrolan and iopromide without EDTA had no effect on the stability at shorter incubation periods of up to 6 days. The addition of Scandicain did not produce low-molecular 90Y or 169Er in the presence of synovial fluid. The fraction of low-molecular 186Re reached 4% after 24 h. Triamcinolone did not have any effect on stability in the presence of synovial fluid. CONCLUSION: The disintegration of the radioactive colloids can be attributed to either the formation of EDTA complexes or radiolytic effects. The volume of the injected contrast agent should be as small as possible to confirm correct intra-articular distribution.     

Differentiation between healthy thyroid remnants and tumor tissue after radioiodine therapy in patients with differentiated thyroid carcinoma using in vitro phosphorus-31 magnetic resonance spectroscopy

BACKGROUND: The growth and spread of many tumors are triggered by changes in cell membrane metabolism, which can lead to systemic alterations in levels of phospholipids. We sought to determine whether plasma levels of several phospholipids could differentiate between healthy remnants of thyroid tissue and residual tumor tissue or metastases in patients with thyroid carcinoma. METHODS: We measured plasma phospholipid levels by phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in blood samples from 30 patients with thyroid cancer who had been rendered hypothyroid in preparation for diagnostic or therapeutic administration of iodine-131. All patients had undergone total thyroidectomy. Iodine-131 whole-body scintigraphy and measurements of thyroglobulin values during up to 3 years of follow-up were used to distinguish patients in remission from those with only healthy thyroid remnants and those with tumor tissue or metastases. RESULTS: Mean (+/- SD) levels of sphingomyelin (0.33 +/- 0.06 mmol/L vs. 0.46 +/- 0.03 mmol/L, P <0.0001) and phosphatidylcholine (1.34 +/- 0.19 mmol/L vs. 2.15 +/- 0.33 mmol/L, P <0.0001) were significantly lower in patients with metastatic thyroid cancer (n = 8) than in patients (n = 12) who were in remission. Patients with only remnants of thyroid tissue (n = 10) also had significantly lower phospholipid levels than did patients in remission, but significantly greater levels that did patients with tumor tissue or metastases. CONCLUSION: These preliminary results suggest that 31P-MRS may be useful in helping to differentiate the presence of tumor tissue, remnants of thyroid tissue not requiring further treatment, and remission in patients with thyroid cancer.     

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.     

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.     

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

PURPOSE: To elucidate the long-term outcome of goniocurettage as a new technique in trabecular microsurgery for advanced open-angle glaucoma. METHODS: In a prospective, nonrandomized clinical trial, 25 eyes of 25 patients with a mean age +/- SD of 72.7+/-10.1 years (range, 50 to 89 years) with uncontrolled chronic open-angle glaucoma that had undergone failed filtering procedures were treated by goniocurettage. Trabecular tissue was scraped away from the chamber angle by means of an instrument similar to a microchalazion curette (diameter, 300 microm). RESULTS: Before surgery, intraocular pressure ranged from 29 to 48 mm Hg (mean +/- SD, 34.7+/-7.1 mm Hg), and mean number of antiglaucoma medications was 2.2+/-0.56. Follow-up averaged (+/-SD) 32.6+/-8.1 months (range, 30 to 45 months). Overall success, defined as postoperative intraocular pressure of 19 mm Hg or less with one pressure-reducing agent, was attained in 15 eyes (60%), with five eyes (20%) being controlled without medication. Considering all successfully treated patients, the mean intraocular pressure was 17.7+/-3.1 mm Hg (range, 10 to 19 mm Hg) at the final visit. Mean intraocular pressure reduction was 17.1+/-7.1 mm Hg in these eyes, representing a net decrease from baseline of 49%. Number of antiglaucoma medications dropped to 0.63+/-0.29. Complications included localized Descemet membrane detachment in five eyes (20%) and moderate anterior chamber bleeding in four eyes (16%). CONCLUSIONS: This new surgical technique can effectively control intraocular pressure for long periods of time in patients with open-angle glaucoma and a history of failed filtering procedures. Goniocurettage may be a suitable alternative to surgical treatment of glaucoma patients with excessive conjunctival scarification.     

Ultrasound biomicroscopy diagnosis of congenital glaucoma

BACKGROUND: In children with congenital glaucoma the assessment of the anterior chamber and the chamber angle might be difficult since scarring and opacities of the cornea are often seen. The purpose of our study was to reveal in vivo--morphology of the anterior segment in patients with congenital glaucoma and opaque cornea. PATIENTS AND METHODS: In 46 eyes of 23 children with different degrees of corneal opacities we performed ultrasoundbiomicroscopy (UBM) of the anterior chamber after having performed a complete ophthalmological examination in general anesthesia. RESULTS: Massive abnormalities of the anterior segment morphology were detected in 5 eyes with completely cloudy cornea. In eyes with partial opacity of the cornea, UBM gave additional information concerning the anterior chamber angle topography, as iris remnants in aniridia, or anterior synechia. CONCLUSION: Especially in cases with extensive corneal opacities the UBM allows us to get morphological and topographic information about the anterior segment and helps to establish an individual strategy for surgical management.