Argon Laser Trabeculoplasty Research Articles

Comparison of primary medicament therapy effects and primary argon laser trabeculoplasty on regulation of intraocular pressure and stability of perimetry findings in open angle glaucoma

Argon Laser Trabeculoplasty (ALT) is a recognized method for reducing intraocular pressure (IOP) in patients with open angle glaucoma. The aim of this study was to compare the effects of primary medicament therapy and primary ALT on IOP regulation and stability of perimetry findings. A total of 50 eyes of 35 patients were treated with primary ALT while 50 eyes of 36 patients were treated with primary medicament therapy with 0.5% timolol with 20, 0.005% latanoprost 18 and with 2% dorzolamid 12 eyes. IOP was controled at 3 months, and the visual field at 6 months during a 30-month follow-up period. In the first 24 months of follow-up there was no statistically significant difference in percentage of eyes with successfully regulated IOP. At 27th and 30th month, in the group primarily treated with medicaments a statistically significant higher percentage of successfully regulated IOP was observed in 98%, and 96% of the eyes, respectively, while in the group primarily treated with ALT the decline in the percentage of successfully regulated IOP was observed in 78% and 76% of the eyes, (chi2-test, p = 0.002, p = 0.140). Both therapy groups showed stability of perimetry findings without statistically significant difference in the values of mean deviation (MD) index until the end of the monitoring period. The dynamics of change in MD index value showed a statistically significant greater decline in this parameter in subjects who had been primarily treated with medications during the last six months of follow-up, (two-factor analysis of variance with a repeated measurement, factor of time x type of therapy, p = 0.030). Primary ALT equally successfully regulates IOP and restores stability of perimetry findings in patients with open angle glaucoma like the primary medicament therapy.

Lasers in primary open angle glaucoma

Lasers have been used in the treatment of primary open angle glaucoma (POAG) over the years, with the hope that they would eventually replace medical and surgical therapy. Laser trabeculoplasty (LT) is an application of argon, diode, or selective laser energy to the surface of the trabecular meshwork to increase the aqueous outflow. The mechanisms by which intraocular pressure (IOP) is lowered could be mechanical, biologic, or by division of adjacent cells. It is commonly used as an adjunct to medical therapy, but is contraindicated if the angle is obstructed, e.g., peripheral anterior synechia (PAS) or developmental glaucomas. About 75% of individuals will show a significant fall in IOP after argon laser trabeculoplasty (ALT), and the response is similar with selective laser trabeculoplasty (SLT). The effects of LT are not always long lasting, with about 10% of individuals showing a rise in IOP with every passing year. Laser thermal sclerostomy, ab interno or externo, is an alternative to other full-thickness filtration procedures. Longer wavelengths in the infrared range have water-absorptive characteristics that facilitate perforation of the sclera. These lasers can be used to avoid intraocular instrumentation and minimize conjunctival trauma.

Long Term Results of Primary Trabeculectomy at King Abdulaziz University Hospital

Long-term efficacy and safety of primary trabeculectomy +/- antimetabolite; assessed by a retrospective study of patients treated at King Abdulaziz University Hospital between, January 1988 and December 2007. Patients who had previous surgery, congenital glaucoma, or follow up in less than 3 years were excluded. Success defined as intraocular pressure ? 21 mmHg with and without medications. Fifty-nine eyes of 59 patients, 30 males and 29 females, with a mean age of 61.4 years were reviewed. Only patients who had primary open angle glaucoma met the inclusion criteria. Mean intraocular pressure was reduced from 25.1 to 16.3 mmHg, with and without anti glaucoma medications in 50 eyes (84.8%) at a mean follow up of 8.5 years. Success rate did not improve significantly (p < 0.7225) with antimetabolite. Life-table showed reduction of success rate over time; 96.6%, 81.2%, and 75.4% at 5, 10 and 15 years, respectively. There was a reciprocal significant association between success rate and the number of pre-operative topical medications (p < 0.0012), and argon laser trabeculoplasty of p < 0.0051). Trainee’s success rates were comparable to that of the principle author. No serious complication was seen. Nine eyes showed deterioration of vision, mainly due to cataract. Primary Trabeculectomy is safe, effective, and a suitable training procedure

Effect of non-surgical ocular hypotensive therapy in normal-tension glaucoma

We investigated the effects of the topical ocular hypotensives with or without half circumference argon laser trabeculoplasty (ALT) on intraocular pressure (IOP) of normal-tension glaucoma (NTG) eyes. Seventy-two NTG patients whose pretreatment mean IOP was > or = 15 mmHg at least in one eye were included and one randomly chosen eye from one patient were used for analysis. They were followed for at least 15 months after commencement of the therapy. The mean pretreatment IOP averaged 17.2 +/- 1.6 mmHg (mean +/- standard deviation, n = 72). All eyes were first treated with topical 2% carteolol. In eyes where IOP reduction was considered unsatisfactory, topical 1% pilocarpine or 0.04% dipivefrine was added. In eyes where IOP reduction was still unsatisfactory even with the two medications, half circumference ALT was performed. Mean IOP reduction was 1.5 mmHg in the eyes treated with topical medications alone and 2.5 mmHg in those treated by topical medications plus ALT. The mean outflow pressure reduction was 16 and 26%, respectively. In 40% of the all eyes, satisfactory IOP reduction was obtained by topical medications with or without additional ALT.

The Effect of Trabeculectomy on Intraocular Pressure of the Untreated Fellow Eye in the Collaborative Initial Glaucoma Treatment Study

To describe the intraocular pressure (IOP) of the untreated fellow eye after unilateral trabeculectomy in the Collaborative Initial Glaucoma Treatment Study (CIGTS). Data collected from a prospective, multicenter, randomized clinical trial. Three hundred patients with newly diagnosed open-angle glaucoma enrolled at 14 centers in the United States who were randomized to initial trabeculectomy. After baseline evaluation and randomization to initial trabeculectomy in the study eye, patients were evaluated at 3 and 6 months and at 6-month intervals thereafter. The IOP was measured by Goldmann applanation tonometry. All eyes included in the analysis were untreated fellow eyes, and the data were censored for potential IOP-lowering events in the fellow eye, including trabeculectomy, argon laser trabeculoplasty, or cataract extraction. Predictive factors for IOP response in the fellow eye to initial trabeculectomy in the study eye were analyzed using a linear mixed model. Intraocular pressure in the untreated fellow eye during follow-up. Although the IOP in the fellow eye was lower than baseline at 3, 6, 12, 18, and 24 months after trabeculectomy in the study eye, this decrease was statistically significant only at month 12 (mean decrease from baseline, 0.73 ± 3.37 mmHg; P = 0.0134). Predictive associations with higher IOP in the fellow eye during follow-up included higher baseline IOP (P < 0.0001), lower level of education (P = 0.0129), time (P = 0.0005), and the presence of other vascular disease (P = 0.0069). Patients who ultimately required fellow eye trabeculectomy (P < 0.0001) or argon laser trabeculoplasty (P<0.0001), but not cataract extraction (P = 0.4597) in the fellow eye, had lower IOPs during follow-up after these procedures. There was no evidence of a substantial effect of trabeculectomy on the IOP of the untreated fellow eye during follow-up. Trabeculectomy does not seem to decrease the mean IOP of the fellow eye, as suggested by some previous studies. Proprietary or commercial disclosure may be found after the references.

A randomized, 36-month, post-marketing efficacy and tolerability study in Sweden and Finland of latanoprost versus non-prostaglandin therapy in patients with glaucoma or ocular hypertension

To compare the effect of time on therapy, efficacy, tolerability and resource utilization of latanoprost or non-prostaglandin analogues (non-PGs) in patients who required a change in intraocular pressure (IOP)-lowering monotherapy. This open-label, multicentre study (Sweden, 19 sites; Finland, seven sites) included adults with glaucoma or ocular hypertension with mean diurnal IOP > or = 21 mmHg on ocular hypotensive monotherapy. Patients were randomized to latanoprost monotherapy or non-PG therapy (commercially available therapy other than a PG) and followed for 36 months. End-points included: time to treatment failure (baseline to visit with a change in/addition to treatment); diurnal IOP (mean of 08.00, 12.00 and 16:00 hr measurements) at months 6, 12, 24 and 36; tolerability; and resource utilization, where analyses used Swedish and Finnish 2006 unit costs. Three hundred and twenty-six patients received >or = 1 dose of latanoprost (n = 162) or non-PGs (n = 164). Median time to treatment failure was longer for latanoprost (36 months) than for non-PGs (12 months; p < 0.001); 51% and 24% of patients remained on randomized therapy after 36 months, respectively (p < 0.001). Decreases in mean diurnal IOP from baseline were significantly greater for latanoprost than for non-PGs at months 6 and 12 (p < 0.01). No serious adverse events were judged to be treatment-related. Mean total 36-month direct costs were similar in patients initiated with latanoprost and non-PGs. Patients who failed previous monotherapy remained on therapy longer when switched to latanoprost. Latanoprost's IOP-reducing effect and tolerability were sustained over the long term. Resource utilization and costs were generally similar in those initiating latanoprost or non-PG therapy.

Verfügbare Lasersysteme und Wirkprinzip der Lasertrabekuloplastik

Intraocular pressure-lowering laser procedures such as argon laser trabeculoplasty and selective laser trabeculoplasty are nowadays an essential part of glaucoma therapy. This article presents the currently most popular laser systems. These various laser procedures are based on the physical structure of the different lasers and on variable generation of laser light. They vary in their effect on the trabecular meshwork on a histopathological level, as well as in the active principles of intraocular pressure reduction. The mechanical, biological, and repopulation theories are currently used to explain the intraocular pressure-lowering effect of the different laser systems; these are discussed in detail.

Pneumatic Trabeculoplasty versus Argon Laser Trabeculoplasty in Primary Open-Angle Glaucoma

Aims: To compare the efficacy of pneumatic trabeculoplasty (PNT) and argon laser trabeculoplasty (ALT) in primary open-angle glaucoma (POAG) uncontrolled with two topical therapies. Methods: In a randomized, prospective clinical study, 32 patients received in 1 eye PNT or ALT. Results: At 1 month, in PNT- and in ALT-treated eyes respectively, mean intraocular pressure (IOP) decreased by 3 ± 2.3 and 5.7 ± 1.7 mm Hg (12.7 ± 9.6 and 24.4 ± 7.4%, both paired t test p < 0.001); 5 and 13 eyes (31 vs. 81%, χ² test p = 0.013) had an IOP reduction ≥20%, 7 and 1 eyes had an insufficient effect (IOP >20 mm Hg). Only 1 PNT-treated eye had IOP reduction ≥20% until 4 months. At 6 months, 10 ALT-treated eyes (62.5%) had IOP reduction ≥20%; 15 PNT- and 3 ALT-treated eyes had an insufficient effect (94 vs. 19%, p < 0.001). Transient anterior segment side effects, but not visual field or fundus changes, occurred after both treatments. Conclusions: PNT is less effective than ALT in POAG uncontrolled with two topical therapies.

Incidence of vitreoretinal complications following cyclophotocoagulation

Dear Editor, We present our data on the risk of vitreoretinal complications after cyclophotocoagulation (CPC). In CPC, the ciliary epithelium is coagulated typically by a transscleral approach [1]. There is intense discussion about uncontrollable hypotonia with the risk of phthisis bulbi as a severe complication of CPC [2, 3]. Little is known about retinal complications of the procedure that are possibly related to a post-operative prostaglandin burst [4, 5]. Our hypothesis is that CPC leads to vitreoretinal complications such as macula edema or epiretinal gliosis. We have retrospectively evaluated 850 consecutive patients who underwent transscleral contact CPC with a diode laser (810 nm) between March 2004 and June 2008, for severe vitreoretinal complications requiring vitreoretinal surgery. The electronic patient files were reviewed for the analysis. In the 850 patients, a total of 1,693 CPC treatments were performed. Of these patients, 20 (2.4% of the patients, 1.2% of the treatments) had to undergo surgery for vitreoretinal conditions after CPC treatment. The diagnoses that led to vitreoretinal surgery were: epiretinal membranes and vitreofoveal traction (12 cases), retinal detachment (four), macular edema (one), choroidal neovascularization (one), endophthalmitis (one) and vitreous haze (one). Age and gender were apparently not risk factors for severe vitreoretinal complications after CPC. The mean age of the 850 patients was 67.5±2.0 years, and in the vitreoretinal complications group 66.4±13.5 years. The male:female ratio was 382:468 (0.816) compared to 8:12 (0.667) respectively. The mean number of CPC treatments applied to all the patients was 2.0±1.4, and to the patients with vitreoretinal complications 1.8±1.1. The average time between the last CPC and the vitreoretinal surgery was 336±39 days. To obtain an indication of whether the number of CPCs influences the risk of severe vitreoretinal complications, a subgroup analysis was done. Table 1 shows the incidence of vitreoretinal surgery for each subgroup. The coefficient of correlation between percentage of vitreoretinal surgery after CPC and total amount of patients in this subgroup was 0.25 (p=0.68). Thus, the number of CPCs does not seem to impact the risk for severe vitreoretinal complications. We carefully reviewed the medical history of each patient who had to undergo vitreoretinal surgery, to determine whether there were other possible reasons for vitreoretinal issues. Without exception, each patient had a history of multiple previous surgeries, and presented with complex combinations of ocular diseases. All had undergone one or more of the following operations: cataract extraction (13 cases), YAG capsulotomy (one), secondary lens implantation (one), deep scelerctomy (eight), YAG goniopuncture (three), trabeculectomy (two), retinal lasercoagulation (four), retinal cryocoagulation (one), or argon laser trabeculoplasty (two). Indications for CPC were: primary open-angle glaucoma (14), PEX-glaucoma (two), traumatic glaucoma (one), neovascular glaucoma (one) and congenital glaucoma (two). In addition to the reasons for Graefes Arch Clin Exp Ophthalmol (2009) 247:1565–1566 DOI 10.1007/s00417-009-1115-5

Selective Laser Trabeculoplasty versus Argon Laser Trabeculoplasty in Patients with Uncontrolled Open-Angle Glaucoma

To compare the efficacy of selective laser trabeculoplasty (SLT) to argon laser trabeculoplasty (ALT) as treatment and retreatment to lower intraocular pressure (IOP) in patients with uncontrolled open-angle glaucoma (OAG) on maximally tolerated medication therapy with a follow-up of 12 months. A total of 120 eyes of 120 patients with uncontrolled OAG were enrolled in the study. Group A included patients with IOP >22 mmHg on maximal medical therapy. A total of 43 eyes underwent SLT treatment and 41 eyes underwent ALT treatment. At the end of the follow-up IOP was <18 mmHg. Group B included patients with IOP >20 mmHg at 3 months follow-up after SLT or ALT treatment. These patients were retreated randomly, 18 with SLT and 18 with ALT. In Group A at the end of the follow-up there was no statistically significant difference in IOP lowering between SLT (6.01 mmHg) and ALT (6.12) (p=0.794). In Group B at the end of the follow-up patients undergoing SLT presented IOP lowering statistically significant to ALT treatment (6.24 mmHg and 4.65 mmHg, respectively, p<0.01). SLT is effective as treatment for patients with OAG and appears to be equivalent to ALT in IOP lowering at 12 months only in patients without a prior treatment. In case of retreatment SLT appears to be better than ALT in IOP lowering.

Titanium:Sapphire Laser Trabeculoplasty Versus Argon Laser Trabeculoplasty in Patients With Open-Angle Glaucoma

To compare the medium-term outcome of titanium:sapphire laser trabeculoplasty (TLT) (SOLX, Inc., Waltham, MA) to argon laser trabeculoplasty (ALT) in patients with uncontrolled open-angle glaucoma. Thirty-seven patients with open-angle glaucoma who had uncontrolled intraocular pressure and no previous filtration surgery participated. Eighteen patients were treated with TLT and 19 patients were treated with ALT. All patients underwent comprehensive eye and visual field examinations. The 18 patients in the TLT group had an average (+/- standard deviation) reduction of 8.3 (+/- 2.7) mm Hg, or 32%, from preoperative intraocular pressure (P < .001). The 19 patients in the ALT group had an average reduction of 6.5 (+/- 4.3) mm Hg, or 25%, from preoperative intraocular pressure (P < .001). Patients in both groups achieved a similar decrease in intraocular pressure (P > .05). Two patients (1 in each group) underwent trabeculectomy and were considered failures. Mean follow-up time was 15 months. TLT provides similar efficacy to ALT in intraocular pressure reduction in patients with open-angle glaucoma. If confirmed in additional studies, TLT may be used as an alternative to ALT in patients with open-angle glaucoma.

Repeat Selective Laser Trabeculoplasty

To evaluate the efficacy of repeat 360-degree selective laser trabeculoplasty (SLT) in glaucoma patients with prior successful 360-degree SLT. Retrospective chart review. Forty-four eyes of 35 patients, > or =18 years of age, with open-angle glaucoma (primary open-angle, pseudoexfoliation, or pigmentary glaucoma), uncontrolled on maximum tolerable medical therapy, underwent an initial 360-degree SLT (SLT1), which was successful for > or =6 months, but eventually lost efficacy and was followed by a repeat 360-degree SLT (SLT2). Patients with prior argon laser trabeculoplasty or other glaucoma surgery, before or during the study period, were excluded. Intraocular pressure (IOP) measurements were recorded before each procedure and 1 to 4 weeks, 1 to 3 months, and 5 to 8 months posttreatment and 15 to 21 weeks after the initial SLT. Reduction in IOP after SLT1 and SLT2 was significantly less with repeat treatment at 1 to 3 months, with average decreases of -5.0 and -2.9 mm Hg, respectively (P=0.01), but there were no statistically significant differences between treatments at the other equivalent time points. Using a definition of "success" as > or =20% peak IOP reduction, success rates for SLT1 and SLT2 were not significantly different. There was also no significant difference in eyes that received SLT2 6 to 12 months after SLT1 compared with those that received SLT2 12 months or more after SLT1. Our findings suggest that repeat 360-degree SLT may be safe and effective after an initially successful 360-degree SLT has failed. These results may be achieved as early as 6 months after the first treatment.

Résultats à deux ans de la trabéculoplastie sélective au laser dans le glaucome à angle ouvert et l’hypertonie oculaire

Selective laser trabeculoplasty (SLT) is a relatively new treatment strategy for the treatment of glaucoma. Its principle is similar to that of argon laser trabeculoplasty (ALT), but may lead to less damage to the trabecular meshwork. We assessed the 2-year efficacy of SLT in a noncomparative consecutive case series. Any adult patient either suspected of having glaucoma or with open-angle glaucoma, whose treatment was judged insufficient to reach target intraocular pressure (IOP), could be recruited. IOP and number of glaucoma treatments were recorded over 2 years after the procedure. Our sample consisted of 44 consecutive eyes of 26 patients, aged 69+/-8 years. Eyes were treated initially on the lower 180 degrees . Three of them were retreated after 15 days on the upper 180. Fourteen eyes had ocular hypertension, 17 primary open-angle/normal-tension glaucoma, 11 pseudoexfoliation (PEX) glaucoma, and two pigmentary glaucoma. Thirty-six eyes had previously been treated and continued to be treated with topical anti-glaucoma medication, ten had had prior ALT, nine iridotomy, and 12 filtering surgery. The 2-year-follow up could not be completed for eight eyes because they needed filtering surgery. In the remaining 36 eyes, IOP decreased by a mean of 17.2%, 3.3 mmHg, (19.2+/-4.7 to 15+/-3.6 mmHg) after 2 years (p<0.001). As a secondary outcome, the number of glaucoma treatments decreased from 1.44 to 1.36 drops/patient. Other results according to subgroups of patients are analyzed: the greatest IOP decrease occurred in eyes that had never been treated with anti-glaucoma medication or with PEX glaucoma. SLT was probably valuable in a few eyes after filtering surgery; however, the statistical power of the study was not strong enough to draw a firm conclusion. When expressed in survival curves after 2 years, however, only 48% and 41% of eyes experienced a decrease of more than 3 mmHg or more than 20% of preoperative intraocular pressure, respectively. SLT decreases IOP somewhat for at least 2 years without an increase in topical glaucoma treatment. However, it cannot totally replace topical glaucoma treatment. In the future, patient selection should be improved to decrease the cost/effectiveness ratio.

III. Asking the Right Question in Laser Trabeculoplasty: “Which Patient”, not “Which Laser”?

The introduction of the Q-switched Nd:YAG laser for selective laser trabeculoplasty (SLT) has raised questions regarding its role in the management of patients with glaucoma. We believe that the most important issue regarding laser trabeculoplasty (LTP) treatment should not be which laser to use, but rather which patients would most benefit from its application. The merits and limitations of SLT have already been presented in the other articles (Argon Laser Trabeculoplasty: The Gold Standard and Selective Laser Trabeculoplasty: A Better Alternative) and, in our opinion, no clinically meaningful differences have been convincingly demonstrated between SLT and argon laser trabeculoplasty (ALT).

I. Argon Laser Trabeculoplasty. The Gold Standard: Argon Laser Trabeculoplasty Versus Selective Laser Trabeculoplasty

The clinical role of laser trabeculoplasty remains a controversial topic with many different opinions. In the following three viewpoints the authors have taken contrasting positions on whether argon laser trabeculoplasty remains the “gold standard” or has been supplanted by selective laser trabeculoplasty. Questions are raised regarding the position of laser trabeculoplasty within the stepping of the treatment paradigm for open-angle glaucoma. The appropriate use of laser trabeculoplasty at different stages of disease severity is analyzed. A broader perspective with new insights on laser trabeculoplasty from these articles will hopefully lead to a better understanding of its clinical role in practice.

Selective Laser Trabeculoplasty

The introduction of selective laser trabeculoplasty (SLT) has renewed interest in laser trabeculoplasty for the reduction of intraocular pressure (IOP) in eyes with glaucoma. This review was undertaken to address frequently raised issues pertinent to SLT in clinical practice. On the basis of the peer-reviewed medical literature, SLT demonstrates equivalent efficacy and comparable safety to argon laser trabeculoplasty, and is also equally as effective as topical medical therapy. SLT's safety profile includes mild and transient inflammation, ocular pain, and a small risk of moderate IOP elevations after the procedure. The mechanism of action of SLT is not known. SLT delivers less energy to the trabecular meshwork and generates less damage to angle tissues. Whether this renders SLT more repeatable than argon laser trabeculoplasty has not been evaluated in published data. SLT seems to be a safe and effective means of IOP reduction in eyes with glaucoma, and can reasonably be applied as primary or adjunctive therapy.

Disc Hemorrhages and Treatment in the Early Manifest Glaucoma Trial

To evaluate the effect of intraocular pressure (IOP)-reducing treatment on the development of disc hemorrhages in patients with glaucoma. Prospective cohort study of patients in the Early Manifest Glaucoma Trial, followed up to 11 years (median = 8 years). Patients with newly detected glaucoma randomized to argon laser trabeculoplasty plus betaxolol (n = 129) or no initial treatment (n = 126), followed with tonometry, perimetry, and ophthalmoscopy every 3 months, and fundus photography every 6 months. Logistic regression expressed as odds ratios (OR) and 95% confidence intervals (CIs), analysis of variance, and Cox time-dependent models, expressed as hazard ratios (HRs) and CIs. Presence (yes/no) and frequency of disc hemorrhages. Disc hemorrhages were identified in approximately 55% of all patients, whether by ophthalmoscopy or review of photographs. In analyses including data up to the time of progression, disc hemorrhages were equally common among treated and control patients: 51.2% versus 45.2%, respectively (P = 0.34), based on ophthalmoscopy, and 50.4% versus 44.4%, respectively (P = 0.34), based on photographs. Gender was the only factor related to the presence of disc hemorrhages detected by both ophthalmoscopy (OR = 0.48; CI, 0.26-0.88; P = 0.022) and photographs (OR = 0.64; CI, 0.38-1.09; P = 0.099) for male patients. The frequency of disc hemorrhages over time did not differ between treated and control patients: 8.4% versus 8.5%, respectively (P = 0.93), based on ophthalmoscopy, and 12.4% versus 11.2%, respectively (P = 0.36), based on photographs. Disc hemorrhages were significantly associated with time to progression (HR = 1.02; CI, 1.01-1.04), and there was no evidence of interaction between treatment group and disc hemorrhages. IOP-reducing treatment was unrelated to the presence or frequency of disc hemorrhages. The results may suggest that disc hemorrhages cannot be considered an indication of insufficient IOP-lowering treatment, and that glaucoma progression in eyes with disc hemorrhages cannot be totally halted by IOP reduction. The results also suggest that disc hemorrhages do not occur in all patients with glaucoma.

Laser Treatment of Glaucoma

AbstractPurpose:To review the historical perspective and the evolution of the laser trabeculoplasty (LT) techniques clinically used for lowering intraocular pressure (IOP) with continuous wave (CW) 514-nm argon LT (ALT), CW 532-nm frequency-doubled Nd:YAG LT (fd Nd:YAG LT), CW 810-nm diode LT (DLT),

Titanium-Sapphire Laser Trabeculoplasty in the Treatment of Open-Angle Glaucoma

Laser trabeculoplasty is accepted as an effective treatment in patients with open-angle glaucoma. Success rates of 30% IOP reduction have been reported although the effect may be temporary.1-4 There are several types of lasers currently used in glaucoma treatment including argon, diode, krypton and neodymium:YAG.2,5-11 Argon laser trabeculoplasty (ALT) is, by far, the most commonly used treatment, but may be associated with early anterior chamber reaction, local irritation, peripheral anterior synechia (PAS) formation and IOP spikes.6,9,11 Argon laser trabeculoplasty is thought to lower IOP by triggering a biological response within the trabecular meshwork (TM). However, scarring of the trabecular meshwork that is associated with ALT limits its effectiveness in subsequent applications. 6,11-14 As a result of this limitation of ALT, selective laser trabeculoplasty (SLT) was developed as a gentler method of IOP reduction without the unnecessary scarring of the trabecular meshwork. Selective laser trabeculoplasty (SLT) utilizes a frequencydoubled neodymium:YAG laser (Nd:YAG SLT) and has been shown to be at least as effective as ALT but with less ocular inflammation and fewer IOP spikes after treatment.1,3,15-19 The lack of trabecular scarring after SLT may allow repeated treatments in patients with previous ALT. We present a third treatment option, Titanium-Sapphire laser trabeculoplasty (TiSLT) that was developed in attempt to improve the efficacy of laser therapy of the trabecular meshwork (Fig. 1). The physical parameters of the Ti-Sapphire laser are: a wavelength of 790 nm; exposure time of 7 mSec, and a spot size of 200 microns. (Figs 2 and 3) Such infrared wavelength is associated with deeper penetration into the TM, affecting tissues like juxta-canalicular region and inner wall of Schlemm’s canal (SC) (Fig. 4). An in vivo study comparing the histology of 3 different lasers (ALT, SLT and TiSLT) in an enucleated human eye confirmed that TiSLT penetrates deeper with disruption of inner wall of Schlemm’s canal (Presented at the unpublished Fig. 1: SOLX 790 laser machine

Evaluation of a Modified Protocol for Selective Laser Trabeculoplasty

To compare the intraocular pressure (IOP) response to a modified protocol for selective laser trabeculoplasty (SLT) to standard protocols for SLT and argon laser trabeculoplasty (ALT). A retrospective study of 318 eyes of 284 patients diagnosed with either primary open angle, pigmentary or pseudoexfoliation glaucoma who underwent laser trabeculoplasty from September 1997 to September 2005. One hundred and two patients, who underwent a modified SLT protocol with 100 overlapping laser spots over 180 degrees of trabecular meshwork were compared with 89 patients who received SLT with 100 nonoverlapping spots over 360 degrees and another 127 patients who received ALT with 50 spots over 180 degrees. IOPs were measured at baseline and postoperatively at 1 hour, 6 weeks, 4 months, and 14 months. Regression models, based on the observed data, were used to predict the fall in IOP in the 3 groups, controlling for differences in baseline pressure. The IOP response to overlapping SLT was significantly worse than to nonoverlapping SLT or ALT, both of which had similar responses. Baseline IOP was the only preoperative factor that predicted response to ALT (P<0.0001) and nonoverlapping SLT (P=0.0019) at all follow-up times. There were no statistically significant predictive factors for IOP reduction in the overlapping SLT group. Overlapping application of SLT results in a poorer IOP response compared with ALT and nonoverlapping SLT.