Trabeculectomy: Proactive Postop Care Reduces Complications

Linda Roach

October 03, 2013

Trabeculectomy controls intraocular pressure (IOP) effectively and has low rates of postoperative complications when patients receive intensive, proactive care after surgery, according to results from a British multicenter study published online September 23 in Ophthalmology.

"There's a commonly held view that although trabeculectomy works, the complication rates are relatively high, so you only do it when a glaucoma patient is in real trouble, and you're looking for very low pressures," study coauthor James F. Kirwan, MA, FRCOphth, told Medscape Medical News. "But what we've shown is that it is much safer than people believe."

"For example, our flat anterior chamber rate is just way down. We had only 2 out of 400-plus patients who had very shallow anterior chambers. Whereas if you look around at the trabeculectomy literature, people will say it's up around 10%," added Dr. Kirwan, a consultant ophthalmologist from the Department of Ophthalmology, Queen Alexandra Hospital, Portsmouth, United Kingdom.

The retrospective, cross-sectional study included 428 consecutive cases of primary trabeculectomy (in 395 individuals) performed at 9 hospital glaucoma units, with a minimum follow-up of 2 years (median follow-up, 40 months; range, 24 - 110 months). Study participants were diagnosed with primary open-angle glaucoma (92%), normal-tension glaucoma (4%), or pseudoexfoliative glaucoma (3%). They had no previous ocular surgeries, other than cataract surgery.

Dr. Kirwan and colleagues found that the total incidence of shallow or flat anterior chambers was 0.9%, and the incidence of hypotony maculopathy was less than 1%. In contrast those complication rates were 10% and 4%, respectively, in the landmark Tube vs Trabeculectomy Study, which reported its 3-year follow-up results in 2009. Rates of other complications are listed in Table 1.

Table 1. Selected Complications and Interventions

Complication or Intervention Percentage
Hyphema 5.8
Bleb leak 13.6
Shallow anterior chamber 0.9
Flat anterior chamber 0
Choroidal detachment 5
Hypotony requiring intervention 3
Iris plug 0.7
Blebitis without endophthalmitis 0.5
Bleb-related endophthalmitis 0.5
Encysted bleb 7.7
Bleb dysesthesia 0.5
5-fluorouracil keratopathy 0.5
Loss of more than 1 line best-corrected vision compared with preoperative values, at 1 year 15
Postoperative 5-fluorouracil subconjunctival injection 28
Bleb needling 17
Suture manipulation 43
Resuturing for bleb leak or hypotony 7
Cataract surgery (based on 363 phakic eyes at study onset) 31
Viscoelastic injection 0.5

The authors documented extensive differences between the techniques used by the surgical practices in the study and those that prevailed at the time of the United Kingdom's 1996 National Survey of Trabeculectomy.

Since 1996, the intraoperative use of antimetabolites to control the eye's healing response has increased more than 10-fold, to 93%, the authors report. Mitomycin C (MMC) also replaced 5-fluorouracil as the preferred medication for this purpose.

Table 2. Intraoperative Use of Antimetabolites (n = 428)

Antimetabolite Cases (%) and Exposure
Mitomycin C 63
 Concentration: 0.2 mg/mL 91
 Concentration: 0.3 mg/mL 2
 Concentration: 0.4 mg/mL 7
5-fluorouracil 30
Mean exposure time, 0.2 mg/mL mitomycin C 2.2 ± 0.7 minutes
Mean exposure time, 5-fluorouracil 3.0 ± 1.7 minutes

Dr. Kirwan attributed the lower complication rates in the surgical practices included in the study (including his own) to their adoption of 3 basic principles.

"One, we treat a large area with antimetabolites, so that you get a broad-based bleb. Two, we tend to do a relatively large flap to try and encourage diffuse and broad leakage of fluid from the eye into the subconjunctival space. Third, and perhaps most important, we are really proactive about not leaving things be," he said.

"So if the eye goes soft, I would resuture it the same day. I would take the patient back into the [operating room], and I would put a couple of stitches into the scleral flap under topical anesthesia."

In addition, use of releasable and adjustable sutures enabled the surgeons to titrate the IOP-lowering effect of the flap by tightening, loosening, or removing sutures, Dr. Kirwan noted. In the study, this occurred in 43% of the eyes; today, he estimates the proportion is closer to 80% in these practices. "A patient might have 20 sutures on day 1, but 10 on month 1," he said.

Table 3. Control of IOP at 2 Years (n = 428)

IOP Measure Outcomes
Mean preoperative IOP mm Hg 23 ± 5.5 mm Hg
Mean postoperative IOP 12.4 ± 4 mm Hg
All eyes: IOP ≤ 21 mm Hg and 20% lower than before the operation 87%
Without postoperative medication  
 IOP ≤ 21 mm Hg and 20% lower than before the operation 80%
 IOP ≤ 18 mm Hg and 20% lower than before the operation 87%

Surgeons whose cases were included in the study followed a protocol that included fornix-based conjunctival peritomy, intraoperative dosing with an antifibrotic, partial-thickness scleral flap, anterior ostium, peripheral iridectomy, and a combination of suture types (releasable, adjustable, and interrupted). This protocol is in general use, with small variations between surgeons, in both the United Kingdom and the United States.

The authors used paired t tests to assess differences in continuously scaled variables before and after surgery, and they considered a P value lower than 0.05 to be statistically significant.

Speaking on behalf of the American Academy of Ophthalmology, Andrew G. Iwach, MD, told Medscape Medical News that clinicians choose from several treatment options on the basis of the individual patient's needs. Someone who swims regularly, for instance, would not be an appropriate candidate for trabeculectomy, he noted.

"It is true that with the refinements of the trabeculectomy procedure, the complications rates are not as high as they used to be. Having said that, one of the challenges of this type of filtering surgery is that one ends up with this little bleb, which could impact the quality of life for that type of patient," Dr. Iwach said. "If we had a predictable way to get the pressure that low and avoid a filtering bleb, I think that most surgeons would like to see that happen."

The authors have disclosed no relevant financial relationships. Dr. Iwach is a consultant for Alcon, Merck, Lumenis, and Elex.

Ophthalmology. Published online September 24, 2013. Abstract


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