Trabeculectomy: Implantable Collagen Matrix vs Mitomycin C

Shuchi B. Patel, MD; Shivani S. Kamat, MD


March 21, 2013

Efficacy and Safety of Collagen Matrix Implants in Phacotrabeculectomy, and Comparison With Mitomycin C Augmented Phacotrabeculectomy at One Year1

Narayanaswamy A, Perera SA, Htoon HM, et al
Clin Experiment Ophthalmol. 2012 Dec 25 [Epub ahead of print]

Seeking a Better Trabeculectomy

Ways to improve trabeculectomy, the gold standard in glaucoma-filtering surgery, are constantly being investigated. Complications of trabeculectomy include hypotony, overfiltration, leaks, and endophthalmitis.[1] The rates of these complications increase with the use of antifibrotic agents, such as mitomycin C (MMC). Yet, without an antifibrotic agent, the rates of failure due to scarring increase. Therefore, an adjunctive agent that could minimize scarring without increasing the complications is much sought after. One such agent that has been proposed for this use is an implantable collagen matrix.

Study Summary

Methods. Narayanaswamy and colleagues conducted a prospective, nonrandomized, comparative study to compare the efficacy and safety of the Ologen™ (Optous, Roseville, California) collagen-matrix implant-modified phacotrabeculectomy compared with phacotrabeculectomy with MMC at 1 year of follow-up. A group of 33 consecutive patients (33 eyes) underwent phacotrabeculectomy with Ologen, and a control group of 33 different patients (33 eyes) had phacotrabeculectomy with MMC. Patients were followed for 12 months before the study results were published. Randomization was not used because the safety and efficacy of Ologen was unproven at the time of the study.

All patients were aged 21 years or older and were diagnosed with primary open-angle glaucoma or primary angle-closure glaucoma with uncontrolled intraocular pressure (IOP). All patients had failed medical and/or laser treatment and had a visually significant cataract. All patients underwent a standard examination at baseline, including best corrected visual acuity, slit-lamp examination, 3 consecutive IOP measurements, gonioscopy, and dilated fundus examination. Before surgery, the groups did not differ significantly on demographic characteristics, glaucoma diagnosis, best-corrected visual acuity, vertical cup-to-disc ratio, or visual field indices.

Intervention. A total of 5 surgeons performed all surgeries in both study groups. All Ologen implant phacotrabeculectomies were started with a fornix-based conjunctival flap and a 4 x 4-mm rectangular scleral flap. A sclerostomy was created using a Kelly punch, followed by a peripheral iridectomy. The scleral flap was sutured with 1 loosely placed suture and 1 releasable 10-0 nylon suture. The Ologen implant (diameter, 7 mm; height, 4 mm) was positioned on top of the scleral flap, and the Tenon capsule and conjunctiva were sutured to the limbus with 10-0 nylon sutures to create a watertight closure.

Phacotrabeculectomy with MMC was performed similarly except that before creating the sclerostomy, 3 polyvinyl sponges (5 x 3 mm in size) were soaked in MMC (0.5 mg/mL) and placed in the subconjunctival area for 2 minutes, followed by copious irrigation using a balanced salt solution. After sclerostomy, 2 fixed sutures were placed to the scleral flap. Phacoemulsification in both cases was performed through a temporal clear corneal incision, with an intraocular lens placed in the capsular bag.

The primary outcome measure was postoperative IOP at month 12, comparing both absolute and percentage changes from baseline. Secondary outcomes included the need for additional postoperative treatments as determined by the surgeon as well as adverse events. Three outcomes were possible:

  • "Complete success": defined as IOP < 18 mm Hg and no need for IOP-lowering medications or needling at 1 year;

  • "Qualified success": defined as IOP < 18 mm Hg but requiring IOP-lowering medications or needling; and

  • "Failure": defined as IOP > 18 mm Hg on 2 consecutive visits or requiring repeat surgery.

Findings. In the Ologen group, the mean reduction in IOP from baseline was 2.9 mm Hg (P = .003) at 1 year, whereas the IOP reduction in the MMC group was 6.9 mm Hg (P < .001). The percentage change in IOP from baseline was 13% in the Ologen group and 26.4% in the MMC group (P = .05).

Preoperatively, the mean number of glaucoma medications was higher in the MMC group (2.0 +/- 0.8) vs the Ologen group (1.55 +/- 0.7, P = .02). The mean preoperative baseline IOP (with medications) was -21.5 +/- 6.5 mm Hg in the MMC group vs 18.4 +/- 4.6 mm Hg in the Ologen group (P = .05). After adjusting for these 2 factors, the difference in IOP reduction between the 2 groups was not statistically significant (P = .16).

Complete success was achieved in 48.5% of those in the Ologen group vs 66.7% in the MMC group (P = .2), and qualified success was seen in 42% vs 21%, in the Ologen and MMC groups, respectively (P = .4). Failure occurred in 3 patients (9.09%) in the Ologen group and in 4 patients (12.1%) in the MMC group (P = .99), although none of these patients required repeat glaucoma surgery.