Beta radiation as an adjunct to low-risk trabeculectomy

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.

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.

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.

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].

Systemic anti-inflammatory fibrosis suppression in threatened trabeculectomy failure

PURPOSE

To provide a rationale for the use of systemic anti-inflammatory fibrosis suppression in the postoperative management of threatened early trabeculectomy bleb failure.

METHODS

A review of the literature and of the authors' own experiences was conducted.

RESULTS

The most important cause of persistent elevation of intraocular pressure after trabeculectomy is unduly marked or persistent inflammation with deposition of fibrous tissue, which prevents the formation of an adequately draining bleb. It was found that a clinically useful degree of suppression of bleb inflammation and fibrosis can be obtained with a 4-6 week course of the combined systemic administration of prednisone (10 mg t.i.d.), a non-steroidal anti-inflammatory agent (e.g. diclofenac 100 mg SR daily) and colchicine (0.25 mg or 0.3 mg t.i.d.), which was termed anti-inflammatory fibrosis suppression. Topical atropine 1% t.i.d. and adrenaline 1% t.i.d. eye drops can also be considered in addition to routine postoperative topical steroids.

CONCLUSIONS

Despite advances in surgical techniques and methods to control fibrosis, anti-inflammatory fibrosis suppression is a valuable tool to have available in the post-operative period for management of trabeculectomies that threaten failure. This regime produces a diffuse bleb, which has a very low risk of late infection or bleb perforation. It is recommend that this regime be added to the list of therapies that are considered when clinical features suggestive of a failing bleb are confronted early in the post-operative course.

Beta irradiation: new uses for an old treatment: a review

Beta radiation has a long history as a treatment modality in ophthalmology. It is a convenient and practical method of applying radiation and has the advantage of minimal tissue penetration. There has been a recent resurgence in the use of beta radiation in other areas in medicine, such as the prevention of restenosis after coronary artery stenting. Beta radiation has been shown in vitro and in vivo to inhibit proliferation of human Tenon's fibroblasts, which enter a period of growth arrest but do not die. Effects on the cell cycle controller p53 have been shown to be important in this process. In ophthalmology, beta radiation has been used widely for the treatment of pterygium and is under evaluation for treatment of age-related macular degeneration and for controlling wound healing after glaucoma drainage surgery. In this latter role, beta radiation may be particularly appropriate for use in developing countries to improve the results of trabeculectomy while potentially avoiding some of the side effects of other antimetabolites.

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

OBJECTIVE

To assess the effect of a single intraoperative application of 750 cGy of beta irradiation on the outcome of trabeculectomy for uncontrolled open-angle glaucoma.

DESIGN

A prospective, randomized, double-blind, placebo-controlled clinical trial.

PARTICIPANTS

Sixty-one eyes of 61 Caucasian patients at low risk of filtering surgery failure, with poorly controlled primary or secondary open-angle glaucoma undergoing routine trabeculectomy.

METHOD

Patients were randomly assigned to control or beta irradiation groups. All patients underwent standard trabeculectomy with fornix-based conjunctival incision. Eyes assigned to beta irradiation received 750 cGy of beta irradiation directly over the sclerostomy site on completion of conjunctival suturing. An identical but inactive applicator was applied to control eyes, delivering no radiation. Both operator and patient remained masked to the assignment for the 12-month follow-up period.

MAIN OUTCOME MEASURES

The main outcome measure was intraocular pressure (IOP) control. Complete success of IOP control was defined as an IOP less than 21 mmHg at 12 months without need for additional medication. Qualified success was defined as an IOP less than 21 mmHg at 12 months where additional medication was required.

RESULTS

Complete success of IOP control was achieved in 19 (86%) control eyes and 35 (90%) irradiated eyes (P = 1.0). Qualified success of IOP control was achieved in 21 (95%) control eyes and 39 (100%) irradiated eyes at 12 months follow-up (P = 1.0)

CONCLUSIONS

We experienced a very high success rate of filtration surgery in this select population without adjunctive irradiation. Our sample size was too small to show any improvement in success with use of beta irradiation in this group. Other studies would have to be done to determine whether it may have measurable benefit in cases with a high risk of filtration failure.