Laser placement in noncontact Nd:YAG cyclophotocoagulation

Cyclodestructive procedures for non-refractory glaucoma

BACKGROUND

Glaucoma is a leading cause of blindness worldwide. It results in a progressive loss of peripheral vision and, in late stages, loss of central vision leading to blindness. Early treatment of glaucoma aims to prevent or delay vision loss. Elevated intraocular pressure (IOP) is the main causal modifiable risk factor for glaucoma. Aqueous outflow obstruction is the main cause of IOP elevation, which can be mitigated either by increasing outflow or reducing aqueous humor production. Cyclodestructive procedures use various methods to target and destroy the ciliary body epithelium, the site of aqueous humor production, thereby lowering IOP. The most common approach is laser cyclophotocoagulation.

OBJECTIVES

To assess the effectiveness and safety of cyclodestructive procedures for the management of non-refractory glaucoma (i.e. glaucoma in an eye that has not undergone incisional glaucoma surgery). We also aimed to compare the effect of different routes of administration, laser delivery instruments, and parameters of cyclophotocoagulation with respect to IOP control, visual acuity, pain control, and adverse events.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2017, Issue 8); Ovid MEDLINE; Embase.com; LILACS; the metaRegister of Controlled Trials (mRCT) and ClinicalTrials.gov. The date of the search was 7 August 2017. We also searched the reference lists of reports from included studies.

SELECTION CRITERIA

We included randomized controlled trials of participants who had undergone cyclodestruction as a primary treatment for glaucoma. We included only head-to-head trials that had compared cyclophotocoagulation to other procedural interventions, or compared cyclophotocoagulation using different types of lasers, delivery methods, parameters, or a combination of these factors.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened search results, assessed risks of bias, extracted data, and graded the certainty of the evidence in accordance with Cochrane standards.

MAIN RESULTS

We included one trial (92 eyes of 92 participants) that evaluated the efficacy of diode transscleral cyclophotocoagulation (TSCPC) as primary surgical therapy. We identified no other eligible ongoing or completed trial. The included trial compared low-energy versus high-energy TSCPC in eyes with primary open-angle glaucoma. The trial was conducted in Ghana and had a mean follow-up period of 13.2 months post-treatment. In this trial, low-energy TSCPC was defined as 45.0 J delivered, high-energy as 65.5 J delivered; it is worth noting that other trials have defined high- and low-energy TSCPC differently. We assessed this trial to have had low risk of selection bias and reporting bias, unclear risk of performance bias, and high risk of detection bias and attrition bias. Trial authors excluded 13 participants with missing follow-up data; the analyses therefore included 40 (85%) of 47 participants in the low-energy group and 39 (87%) of 45 participants in the high-energy group.Control of IOP, defined as a decrease in IOP by 20% from baseline value, was achieved in 47% of eyes, at similar rates in the low-energy group and the high-energy groups; the small study size creates uncertainty about the significance of the difference, if any, between energy settings (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.64 to 1.65; 79 participants; low-certainty evidence). The difference in effect between energy settings based on mean decrease in IOP, if any exists, also was uncertain (mean difference (MD) -0.50 mmHg, 95% CI -5.79 to 4.79; 79 participants; low-certainty evidence).Decreased vision was defined as the proportion of participants with a decrease of 2 or more lines on the Snellen chart or one or more categories of visual acuity when unable to read the eye chart. Twenty-three percent of eyes had a decrease in vision. The size of any difference between the low-energy group and the high-energy group was uncertain (RR 1.22, 95% CI 0.54 to 2.76; 79 participants; low-certainty evidence). Data were not available for mean visual acuity and proportion of participants with vision change defined as greater than 1 line on the Snellen chart.The difference in the mean number of glaucoma medications used after cyclophotocoagulation was similar when comparing treatment groups (MD 0.10, 95% CI -0.43 to 0.63; 79 participants; moderate-certainty evidence). Twenty percent of eyes were retreated; the estimated effect of energy settings on the need for retreatment was inconclusive (RR 0.76, 95% CI 0.31 to 1.84; 79 participants; low-certainty evidence). No data for visual field, cost effectiveness, or quality-of-life outcomes were reported by the trial investigators.Adverse events were reported for the total study population, rather than by treatment group. The trial authors stated that most participants reported mild to moderate pain after the procedure, and many had transient conjunctival burns (percentages not reported). Severe iritis occurred in two eyes and hyphema occurred in three eyes. No instances of hypotony or phthisis bulbi were reported. The only adverse outcome that was reported by the treatment group was atonic pupil (RR 0.89 in the low-energy group, 95% CI 0.47 to 1.68; 92 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

There is insufficient evidence to evaluate the relative effectiveness and safety of cyclodestructive procedures for the primary procedural management of non-refractory glaucoma. Results from the one included trial did not compare cyclophotocoagulation to other procedural interventions and yielded uncertainty about any difference in outcomes when comparing low-energy versus high-energy diode TSCPC. Overall, the effect of laser treatment on IOP control was modest and the number of eyes experiencing vision loss was limited. More research is needed specific to the management of non-refractory glaucoma.

Long-term results of noncontact neodymium:yttrium-aluminum-garnet cyclophotocoagulation in neovascular glaucoma

PURPOSE

To determine the long-term efficacy and safety of noncontact transscleral neodymium:yttrium-aluminum-garnet (Nd:YAG) cyclophotocoagulation (CP) for the treatment of neovascular glaucoma (NVG).

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

One hundred fifteen eyes of 111 subjects treated from December 1987 to January 2001.

METHODS

Eyes with uncontrolled NVG underwent noncontact Nd:YAG CP. Treatment parameters and pretreatment and posttreatment intraocular pressures (IOP) were reviewed. Preoperative and postoperative IOP were compared using a paired Student's t test. Success was defined as an IOP </=22 mmHg, with or without medications, in the absence of phthisis bulbi, and without having undergone further surgical procedures. Results were subjected to a Kaplan-Meier life-table analysis.

RESULTS

Mean follow-up was 27.0 +/- 34.3 months (range, 1-148 months). Mean preoperative IOP was 47.4 +/- 11.1 mmHg (range, 26-70 mmHg). Mean postoperative IOP was 18.3 +/- 12.2 mmHg (range, 0-44 mmHg). The mean number of treatment sessions was 1.4 +/- 0.7 (range, 1-6), with 82 eyes (71.3%) having only one treatment. Kaplan-Meier survival analysis showed a probability of continued success at 1 year of 65.0%, at 3 years of 49.8%, and at 6 years of 34.8%. Phthisis developed in 8.6% of the eyes.

CONCLUSIONS

Noncontact Nd:YAG CP provides long-term IOP reduction in eyes with medically uncontrolled NVG. This can be associated with complications that include inflammation, visual loss, and hypotony. Repeat treatment may be necessary.

Long-term results of noncontact transscleral neodymium:YAG cyclophotocoagulation

PURPOSE

To determine the long-term efficacy of noncontact transscleral neodymium:YAG (Nd: YAG) cyclophotocoagulation.

METHODS

A retrospective analysis was made of 167 patients (173 eyes) with intractable glaucoma treated with noncontact Nd:YAG cyclophotocoagulation between December 1987 and November 1993, reviewing the treatment parameters, complications, and pre- and posttreatment intraocular pressure (IOP). The IOP was compared using a Student's t test, and the results were subjected to a Kaplan-Meier life-table analysis. Success was defined as an IOP of 22 mmHg or lower in the absence of phthisis and without having undergone any additional surgical procedures.

RESULTS

Mean follow-up was 30.5 +/- 22.8 months. Mean preoperative IOP was 40.0 +/- 12.9 mmHg. Mean postoperative IOP was 19.8 +/- 11.4 mmHg (P < 0.05). The mean number of treatment sessions was 1.8 +/- 1.3 (range, 1-8) with 95 eyes (55%) having only one treatment. Kaplan-Meier survival analysis showed a probability of continued success at 3 years of approximately 73% and at 5 years of 45%. Complications included loss of two or more lines of Snellen visual acuity or one or more categories in the low-vision range (40%), phthisis (6.9%), epithelial defects (1.9%), and hyphema (0.6%).

CONCLUSION

This study suggests that Nd:YAG transscleral cyclophotocoagulation provides a useful long-term reduction of IOP in eyes with advanced or complicated glaucoma, but there is a significant risk of visual loss associated with the procedure.

A clinicopathologic correlative study of noncontact transscleral Nd:YAG cyclophotocoagulation

We studied the histopathologic changes of three eyes enucleated two weeks, eight weeks, and 17 months, respectively, after noncontact Nd:YAG cyclophotocoagulation. The histologic findings at two weeks were destruction of the nonpigmented and pigmented ciliary body epithelium, occlusion of the capillaries of the ciliary processes, and ciliary body stromal necrosis in the region of the processes. Hyperplasia of the pigmented and nonpigmented epithelium, fibrosis and near total atrophy of the ciliary processes, and partial atrophy of the ciliary muscles were present at eight weeks and 17 months. We concluded that application of treatment 1.0 to 1.5 mm posterior to the corneoscleral limbus selectively destroys the pars plicata, and that, histologically, the mechanism for reducing intraocular pressure appears to be destruction of ciliary processes with reduction of aqueous formation.

Ophthalmic laser microendoscope ciliary process ablation in the management of neovascular glaucoma

PURPOSE

To evaluate the potential efficacy of ophthalmic laser microendoscope photocoagulation of the ciliary processes in the management of intractable neovascular glaucoma.

METHODS

Ten patients with intractable neovascular glaucoma underwent ophthalmic laser microendoscope ciliary process ablation via a pars plana incision. The device and surgical technique are discussed.

RESULTS

Preoperative intraocular pressure (IOP) ranged from 36 mmHg to 62 mmHg (mean, 43.6 mmHg). Postoperative final IOP ranged from 3 mmHg to 27 mmHg (mean, 15.3 mmHg). This represents an absolute decrease of 28.3 mmHg (65%). Postoperatively, 9 eyes had an IOP of less than 21 mmHg, although 3 of these eyes required medication. One eye attained a final IOP of 27 mmHg. All eyes were treated once. Nine patients were treated with carbonic anhydrase inhibitors preoperatively, and six patients were able to discontinue this medication postoperatively. Phthisis was not observed, but hypotony evolved in two eyes with chronic retinal detachment. Follow-up ranged from 6 to 11 months (mean, 8.8 months).

CONCLUSION

This new therapeutic modality, which combines endoscopic visualization of the ciliary processes with diode laser photocoagulation, can be effective in the management of intractable neovascular glaucoma.