Randomized controlled clinical trial of beta irradiation as an adjunct to trabeculectomy in open-angle glaucoma

Augmented Subscleral Trabeculectomy With Beta Radiation and Mitomycin C in Egyptian Glaucoma Patients

PURPOSE

Subscleral trabeculectomy is the most common surgical treatment for glaucoma. However, wound healing and scar formation may result in bleb fibrosis, leading to bleb failure. The healing response of the wound is reported to be the single most important risk factor in determining the final intraocular pressure (IOP) after glaucoma filtration surgery. Thus, we aimed to evaluate the effect of preoperative beta irradiation and intraoperative mitomycin C (MMC) treatment as combined adjuncts to subscleral trabeculectomy in the management of glaucoma in Egyptian patients.

PATIENTS AND METHODS

This prospective, interventional, comparative masked clinical study was performed between October 2016 and January 2018. This study included 50 subjects, 25 of whom underwent trabeculectomy augmented by MMC intraoperatively and beta radiation preoperatively at the bleb area (patient group #1). The remaining 25 subjects underwent trabeculectomy with MMC alone (control group #2). Beta radiation was administered 5 to 7 days before the surgery as a single dose (1000 cGy) using a strontium-90 probe. MMC (0.2 mg/mL) was administered for 2 minutes.

RESULTS

There was a statistically significant difference in postoperative IOP between the groups from the second week. Intraoperative hyphema occurred in 6 cases in the control group #2, whereas no intraoperative hyphema was observed in patient group #1; this difference was statistically significant.

CONCLUSIONS

Subscleral trabeculectomy augmented by beta radiation and MMC gives greater control over IOP. Therefore, we recommend using beta radiation before trabeculectomy in patients who may have a high risk of developing conjunctival fibrosis.

Glaucomagenesis following ionizing radiation exposure

Glaucoma is a group of optic neuropathies causing optic nerve damage and visual field defects, and is one of the leading causes of blindness. Nearly a century has passed since the first report of glaucoma manifested following ionizing radiation therapy of cancers. Nevertheless, associations between glaucoma and radiation exposures, a dose response relationship, and the mechanistic underpinnings remain incompletely understood. Here we review the current knowledge on manifestations and mechanisms of radiogenic glaucoma. There is some evidence that neovascular glaucoma is manifest relatively quickly, within a few years after high-dose and high dose-rate radiotherapeutic exposure, but little evidence of excess risks of glaucoma after exposure to much lower doses or dose rates. As such, glaucoma appears to have some of the characteristics of a tissue reaction effect, with a threshold of at least 5 Gy but possibly much higher.

Current and Future Techniques in Wound Healing Modulation after Glaucoma Filtering Surgeries

Filtering surgeries are frequently used for controlling intraocular pressure in glaucoma patients. The long-term success of operation is intimately influenced by the process of wound healing at the site of surgery. Indeed, if has not been anticipated and managed accordingly, filtering surgery in high-risk patients could end up in bleb failure. Several strategies have been developed so far to overcome excessive scarring after filtering surgery. The principal step involves meticulous tissue handling and modification of surgical technique, which can minimize the severity of wound healing response at the first place. However, this is usually insufficient, especially in those with high-risk criteria. Thus, several adjuvants have been tried to stifle the exuberant scarring after filtration surgery. Conventionally, corticosteroids and anti-fibrotic agents (including 5-fluorouracil and Mitomycin-C) have been used for over three decades with semi-acceptable outcomes. Blebs and bleb associated complications are catastrophic side effects of anti-fibrotic agents, which occasionally are encountered in a subset of patients. Therefore, research continues to find a safer, yet effective adjuvant for filtering surgery. Recent efforts have primarily focused on selective inhibition of growth factors that promote scarring during wound healing process. Currently, only anti-VEGF agents have gained widespread acceptance to be translated into routine clinical practice. Robust evidence for other agents is still lacking and future confirmative studies are warranted. In this review, we explain the importance of wound healing process during filtering surgery, and describe the conventional as well as potential future adjuvants for filtration surgeries.

Angiogenesis in glaucoma filtration surgery and neovascular glaucoma: A review

Angiogenesis may pose a clinical challenge in glaucoma, for example, during the wound healing phase after glaucoma filtration surgery and in the severe secondary glaucoma called neovascular glaucoma (NVG). Upregulation of vascular endothelial growth factor (VEGF), a key mediator of angiogenesis, occurs in eyes that have undergone glaucoma filtration surgery, as well as those with NVG. This has led investigation of the ability of anti-vascular endothelial growth factor therapy to improve outcomes, and we examine the findings with respect to the safety and efficacy of anti-vascular endothelial growth factor agents, mainly bevacizumab and ranibizumab, in eyes that have undergone glaucoma filtration surgery or have NVG. Combining conventional therapies-such as antimetabolites after filtration surgery and panretinal photocoagulation in NVG-and anti-vascular endothelial growth factor drugs may produce a synergetic effect, although further studies are required to evaluate the long-term efficacy of combination treatments.

[Options for prolonging the hypotensive effect of trabeculectomy]

OBJECTIVE

To assess potential of preoperative therapy with local steroid and non-steroid anti-inflammatory drugs (SAIDs and NSAIDs) for prolonging the hypotensive effect of trabeculectomy.

MATERIAL AND METHODS

A total of 80 patients with primary open-angle glaucoma planed for trabeculectomy were randomized into 4 groups of 20 each: 3 groups that differed in the studied drug (nepafenac, dexamethasone, or their non-fixed combination) and a control group with no preoperative therapy. The patients instilled 1 drop of either drug b.i.d. for 2 weeks before the surgery and were examined each day of the first week and then at weeks 1, 2, 4 and months 3, 6, and 12. The rate of postoperative surgical and medical interventions (needling, needling revision, hypotensive therapy) was used for outcome evaluation.

RESULTS

Postoperative needling was required in 50% of the controls, 35% of the NSAIDs and 30% of the SAIDs patients as well as 20% the combination-therapy patients. Needling revision had to be performed in 10% of patients from the control group and 5% of patients from the NSAIDs group. Patients from the steroid and combination-therapy groups had no need in needling procedure. Further hypotensive therapy was required in 50% of the control group, 35% of the NSAIDs group, 25% of the SAIDs group and 20% of the combination-therapy group. During the first postoperative year complete success of the treatment was achieved in 50% of the controls, 65% of the NSAIDs patients, 75% of the SAIDs patients, and 80% of those under combination therapy. Qualified success during the same period was achieved in 100% of cases.

CONCLUSION

Preoperative local anti-inflammatory therapy helped to increase the one-year complete success rate after trabeculectomy as compared with the controls. The most significant hypotensive effect was noted in the combination-therapy group (80%), less significant--in the steroid and non-steroid monotherapy groups (75% and 65% correspondingly). A negative correlation was noted between the use of nepafenac and dexamethasone and other measures aimed at increasing the hypotensive effect of glaucoma surgery.

Wound modulation after filtration surgery

Filtration surgery is the standard invasive procedure for the management of intraocular pressure in advanced glaucoma. The key to a successful outcome is to modulate the normal wound healing cascade that leads to closure of the newly created aqueous outflow pathway. Antifibrotic agents such as mitomycin C and 5-fluorouracil have been increasingly used to modulate the wound healing process and increase surgical success. Although these agents have proven efficacy, they also increase the risk of complications. Efforts have centered on the identification of novel agents and techniques that can influence wound modulation without these complications. We detail new agents and methods under investigation to control wound healing after filtration surgery.

Beta radiation for glaucoma surgery

BACKGROUND

The outcome of glaucoma surgery can be affected by the rate at which the surgical wound heals. Beta radiation has been proposed as a rapid and simple treatment to slow down the healing response.

OBJECTIVES

To assess the effectiveness of beta radiation during glaucoma surgery (trabeculectomy).

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 3), MEDLINE (January 1950 to March 2012), EMBASE (January 1980 to March 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 26 March 2012.

SELECTION CRITERIA

We included randomised controlled trials comparing trabeculectomy with beta radiation to trabeculectomy without beta radiation.

DATA COLLECTION AND ANALYSIS

We collected data on surgical failure (intraocular pressure > 21 mmHg), intraocular pressure and adverse effects of glaucoma surgery. We pooled data using a fixed-effect model.

MAIN RESULTS

We found four trials that randomised 551 people to trabeculectomy with beta irradiation versus trabeculectomy alone. Two trials were in Caucasian people (126 people), one trial in black African people (320 people) and one trial in Chinese people (105 people). People who had trabeculectomy with beta irradiation had a lower risk of surgical failure compared to people who had trabeculectomy alone (pooled risk ratio (RR) 0.23 (95% CI 0.14 to 0.40). Beta irradiation was associated with an increased risk of cataract (RR 2.89, 95% CI 1.39 to 6.0).

AUTHORS' CONCLUSIONS

Trabeculectomy with beta irradiation has a lower risk of surgical failure compared to trabeculectomy alone. A trial of beta irradiation versus anti-metabolite is warranted.

Preoperative nonsteroidal anti-inflammatory drug or steroid and outcomes after trabeculectomy: a randomized controlled trial

PURPOSE

To investigate the benefit of preoperative treatment with either topical nonsteroidal anti-inflammatory drug (NSAID) or steroid in terms of clinical outcomes following trabeculectomy.

DESIGN

Prospective, randomized placebo-controlled trial.

PARTICIPANTS

Sixty-one patients.

METHODS

Between July 2005 and October 2007, 61 consecutive medically uncontrolled glaucoma patients scheduled for first-time trabeculectomy were randomized to 1 of 3 study topical medication groups: nonsteroidal anti-inflammatory drugs (ketorolac), steroids (fluorometholone), or placebo (artificial tears). Patients instilled 1 drop 4 times daily for 1 month before the procedure and were examined on days 1 and 2, at weeks 1, 2, and 4, and at months 3, 6, 12, 18, and 24 after trabeculectomy.

MAIN OUTCOME MEASURES

Incidence of postoperative surgical or medical interventions (needling, laser suture lysis, needling revision, and intraocular pressure [IOP]-lowering medication).

RESULTS

Fifty-four patients (54 eyes) were entered for analysis. The mean number of preoperative medications was 2.3+/-0.9. The mean baseline IOP was 21.0+/-6.0 mmHg. The mean postoperative target IOP was 16.5+/-1.8 mmHg. The mean follow-up was 23.6+/-4.0 months. The percentage of patients requiring needling within the first year was 41% in the placebo group, 6% in the NSAID, and 5% in the steroid group (P = 0.006). The percentage of patients requiring IOP-lowering medication to reach the target IOP at 1 year was 24% in the placebo group, 18% in the NSAID group, and 0% in the steroid group (P = 0.054 overall; P = 0.038 for steroids vs. others). The log-rank test showed a significant (P = 0.019) difference in medication-free survival curves between the different groups. More specifically, patients in the steroid group needed significantly less medication over the total follow-up (P = 0.007).

CONCLUSIONS

Topical ketorolac or fluorometholone for 1 month before surgery was associated with improved trabeculectomy outcomes in terms of likelihood of postoperative needling. In the steroid group, there was a significantly reduced need for additional postoperative IOP-lowering medication compared with the other groups.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Moving the goal posts definitions of success after glaucoma surgery and their effect on reported outcome

PURPOSE

To determine (1) the extent to which the definition of success of glaucoma surgery varies in the literature and (2) the degree to which the reported outcome after trabeculectomy is affected by the criteria used to define success.

DESIGN

A systematic review of the literature and application of definitions to a retrospective cohort.

PARTICIPANTS

A cohort of 100 patients who previously underwent trabeculectomy.

METHODS

A literature search was performed of PubMed using the search term trabeculectomy for a 5-year period. Studies presenting original data relating to longitudinal intraocular pressure (IOP) control after glaucoma surgery were included. The definitions of success and failure used were documented for each publication. Each IOP-related definition of success was applied to a cohort of patients who previously underwent trabeculectomy. Success rates were derived for each published definition up to 36 months after surgery.

MAIN OUTCOME MEASURES

Intraocular pressure measured by Goldmann applanation tonometry.

RESULTS

From 100 publications meeting the inclusion criteria, 92 distinct IOP-related definitions of success were identified. Using these definitions, success rates for this series of 100 trabeculectomies varied between 36.0% and 98.0% after 3 years of follow-up.

CONCLUSIONS

Over a recent 5-year period, there were nearly as many different definitions of success after glaucoma surgery as publications on the subject. The definition used markedly affects the quoted success rate after trabeculectomy, making interpretation of and comparison between published results extremely difficult. Standardization of published outcome parameters after glaucoma surgery is essential to allow meaningful comparisons between different study reports.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Beta radiation for glaucoma surgery

BACKGROUND

The outcome of glaucoma surgery can be affected by the rate at which the surgical wound heals. Beta radiation has been proposed as a rapid and simple treatment to slow down the healing response.

OBJECTIVES

To assess the effectiveness of beta radiation during glaucoma surgery (trabeculectomy).

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (which includes the Cochrane Eyes and Vision Group Trials Register) (Issue 4 2008), MEDLINE (January 1966 to October 2008) and EMBASE (January 1980 to October 2008). The databases were last searched on 24 October 2008.

SELECTION CRITERIA

We included randomised controlled trials comparing trabeculectomy with beta radiation to trabeculectomy without beta radiation.

DATA COLLECTION AND ANALYSIS

We collected data on surgical failure (intraocular pressure > 21 mmHg), intraocular pressure and adverse effects of glaucoma surgery. We pooled data using a fixed-effect model.

MAIN RESULTS

We found four trials that randomised 551 people to trabeculectomy with beta irradiation versus trabeculectomy alone. Two trials were in Caucasian people (126 people), one trial in black African people (320 people) and one trial in Chinese people (105 people). People who had trabeculectomy with beta irradiation had a lower risk of surgical failure compared to people who had trabeculectomy alone (pooled risk ratio (RR) 0.23 (95% CI 0.14 to 0.40). Beta irradiation was associated with an increased risk of cataract (RR 2.89, 95% CI 1.39 to 6.0).

AUTHORS' CONCLUSIONS

Trabeculectomy with beta irradiation has a lower risk of surgical failure compared to trabeculectomy alone. A trial of beta irradiation versus anti-metabolite is warranted.

The long-term effect of experimental beta-radiation therapy on the human cornea

BACKGROUND

Radiation treatment of the human eye has been utilized in the United States since the early 1900s. Beta-radiation therapy was generally accepted by the medical community as a treatment option for a wide variety of anterior and posterior segment conditions from 1930 to the early 1950s. By the 1960s, beta-radiation therapy had fallen out of favor due to dangerous side effects; however an updated radiation procedure is now in use in ophthalmology to treat anterior and posterior segment disease.

CASE REPORT

A 64-year-old Caucasian female presented for a routine eye examination with a history of experimental beta-radiation treatments to the eyes as a teenager. A high astigmatic refractive error was present and best corrected visual acuity was 20/40 OD, 20/30 OS. Slit lamp examination showed severe disruption throughout the lower third of both corneas, appearing densely calcified with inferior vascularization. The left eye had a central descemetocele. The patient's ocular and visual conditions were relatively stable and required no special treatment as of the writing of this report, decades after her original treatments.

CONCLUSION

This patient is one example of the long-term effect of beta-radiation treatment on the eye. Ongoing care is needed to monitor the ocular health and vision of these individuals as radiation effects may necessitate observation and/or care throughout the patient's lifetime. Follow-up on more patients who underwent beta-radiation treatment decades ago, should it be possible to do so, would provide further insight into the long-term anterior segment changes that can occur as a result of such treatment.

Effect of beta radiation on success of glaucoma drainage surgery in South Africa: randomised controlled trial

OBJECTIVE

To evaluate whether beta radiation may offer a practical method of improving surgical success for glaucoma drainage surgery in South Africa.

DESIGN

Double blind, randomised controlled trial.

SETTING

Three public hospitals in South Africa.

PARTICIPANTS

450 black Africans with primary glaucoma.

INTERVENTIONS

Trabeculectomy with 1000 cGy beta radiation or standard trabeculectomy without beta radiation (placebo).

MAIN OUTCOME MEASURES

Primary outcome measure was surgical failure within 12 months (intraocular pressure > 21 mm Hg while receiving no treatment for ocular hypotension). Secondary outcomes were visual acuity, surgical reintervention for cataract, and intraoperative and postoperative complications.

RESULTS

320 people were recruited. beta radiation was given to 164; 20 (6%) were not seen again after surgery. One year after surgery the estimated risk of surgical failure was 30% (95% confidence interval 22% to 38%) in the placebo arm compared with 5% (2% to 10%) in the radiation arm. The radiation group experienced a higher incidence of operable cataract (18 participants) than the placebo group (five participants; P = 0.01). At two years the estimated risks with placebo and beta radiation were, respectively, 2.8% (0.9% to 8.3%) and 16.7% (10.0% to 27.3%).

CONCLUSION

beta radiation substantially reduced the risk of surgical failure after glaucoma surgery. Some evidence was, however, found of an increased risk for cataract surgery (a known complication of trabeculectomy) in the beta radiation arm during the two years after surgery.

TRIAL REGISTRATION

ISRCTN62430622 [controlled-trials.com].

The effects of single doses of beta radiation on the wound healing behaviour of human Tenon's capsule fibroblasts

AIM

To determine the effects of single doses of beta radiation on the wound healing functions of human Tenon's capsule fibroblasts (hTf).

METHODS

hTf were grown in tissue culture and irradiated with beta radiation using a strontium 90 source. The effects of beta radiation on fibroblast migration was studied using microporous transwell membranes. The effects of radiation on fibroblast contraction was investigated using a fibroblast populated collagen gels model. Production of extracellular matrix molecules (collagen I, collagen III, and fibronectin) by monolayers of irradiated fibroblasts was quantified for 14 days following single doses of beta radiation.

RESULTS

Growth inhibiting doses of beta radiation did not inhibit fibroblast migration or contraction at any time point. Levels of soluble fibronectin from irradiated populations were significantly reduced after >500 cGy beta radiation. Collagen I and III levels were not reduced after any dose of radiation, and increased following treatment with 1000 cGy beta radiation.

CONCLUSIONS

Growth arresting doses of beta radiation have unique effects on the wound healing behaviour of human Tenon's capsule fibroblasts. There was no significant effect on cellular migration or contraction, but ECM production was altered. Fibronectin production was inhibited following higher radiation doses, and collagen I and III production increased after 1000 cGy. The effects of single doses of beta radiation on ocular fibroblast wound healing behaviour are very different from those of 5-fluorouracil and mitomycin C, and these differences may be exploited clinically in the regulation of wound healing after glaucoma filtration surgery.

Trabeculectomy with beta radiation: long-term follow-up

PURPOSE

To evaluate the long-term outcome and complications of trabeculectomy with beta radiation.

DESIGN

Retrospective noncomparative case series.

PARTICIPANTS

Forty-three patients with confirmed primary open-angle glaucoma (POAG), who received trabeculectomy with adjunctive beta radiation at the Prince of Wales Hospital between June 1991 and November 1994.

METHODS

Patients fulfilling the preceding criteria were followed up longitudinally. The visual acuity, intraocular pressure (IOP), bleb morphology, and complications were evaluated.

MAIN OUTCOME MEASURES

Visual acuity, IOP, bleb morphology, complications.

RESULTS

Forty-three eyes of 43 consecutive Chinese patients were recruited and successfully followed up for a minimum of 7 years. The mean age +/- 1 standard deviation (SD) was 60.9 +/- 13.0 years. There were 29 males and 14 females. The mean baseline IOP +/- 1 SD was 28.3 +/- 5.8 mmHg. The mean postoperative IOP +/- 1 SD after the initial trabeculectomy was 11.9 +/- 4.3 mmHg, and the mean number of preoperative IOP-lowering eyedrops +/- 1 SD was reduced from 2.8 +/- 0.5 to 0.7 +/- 1.0 at 7 years follow-up. The qualified success rate at 7 years follow-up, defined as IOP <or=21 mmHg with and without medication(s), was 88.4%. The complete success rate at 7 years defined as IOP <or=21 mmHg without medication was 60.7%. Two eyes developed blebitis, and one of them progressed to corneal decompensation after the infection. One eye had hypotony, and one eye had a traumatic ruptured bleb. Twelve eyes (27.9%) developed significant cataract. No corneal ulceration or scleral necrosis was encountered.

CONCLUSIONS

From this noncomparative study, trabeculectomy with a single dose of 1000 rad beta radiation used as an adjunctive measure for POAG in Chinese eyes had achieved a qualified success rate of 88.4% at 7 years.