Thierry Zeyen, MD, PhD
|
Since the late 1960s, trabeculectomy has been the operation of choice for improving aqueous outflow in glaucomatous eyes.
Still today it remains the gold standard for glaucoma filtration surgery, with ophthalmologists accumulating a considerable
amount of experience with the procedure, its advantages and its limitations.
Though the traditional surgery is effective in achieving an intraocular pressure (lOP) of less than 22 mmHg, it is less successful
in achieving IOPs of less than 15 mmHg, which is a safer level to minimize field progression in advanced glaucoma. The traditional
technique is also associated with cataract- and bleb-related problems as well as infrequent but potentially serious postoperative
complications, such as endophthalmitis, choroidal haemorrhage and hypotonous maculopathy.
Current concepts of success in glaucoma surgery reflect a greater awareness of these complications and the need for tight
control of IOP. Even with numerous modifications that have been proposed to the original trabeculectomy, the lack of a reproducible
postoperative IOP reduction and the potential complications have led several surgeons to try other techniques, such as non-perforating
surgery.
Improving on a traditional technique
Here, Ingeborg Stalmans and Thierry Zeyen of the University Hospital, Leuven, Belgium, investigate the long-term outcome of
a new trabeculectomy technique, developed by Peng Khaw,1 which aims to address certain drawbacks relating to the classic method.
Specifically, the Peng Khaw technique has identified the following complications relating to the standard trabeculectomy:
- Variable filtration which, if excessive, could lead to a flat anterior chamber (AC), hypotony, maculopathy, choroidal detachment
or haemorrhage, aqueous misdirection or cataract.2 Ocular massage and/or laser suture lysis are often necessary in order to reach the target postoperative IOP. However, laser
suture lysis is non-titratable, sometimes impossible to perform, and may result in over-drainage and hypotony.
- Flat chamber and hypotony during the procedure increase the risk of complications such as choroidal haemorrhage, macular wipeout
and corneal decompensation; all vision-threatening conditions.
- Inflammatory response stimulated by debris remaining at trabeculectomy site could induce fibrosis.
Figure 1: Adjustable sutures (Courtesy of T. Missotten).
|
On this basis, the Peng Khaw technique adopts the use of a combination of releasable and adjustable sutures, an AC maintainer
and a punch to produce a standard and consistent trabeculectomy aperture. Zeyen and his team have identified several distinct
advantages of this technique, which includes controlled outflow because of the postoperative adjustment of sutures, which
allow careful titration of filtration. AC is maintained and hypotony prevented during the procedure, and inflammatory factors
are flushed away from the trabeculectomy site by the AC maintainer, thus reducing risk of bleb failure. During the procedure,
a fornix-based conjunctival flap is dissected, which results in good visualization of the surgical field and allows the aqueous
humour to drain posteriorly, promoting the formation of a diffuse bleb.3 Although a higher risk of bleb leakage has been associated in the past with this form of dissection,4 this trabeculectomy method adopts the use of the "purse-string" technique, augmented with mattress sutures in between whenever
necessary, to close the conjunctiva, thus preventing persistent bleb leakage. Long-term outcome
In a retrospective study, published in the January 2006 issue of the British Journal of Ophthalmology,5 Stalmans and colleagues evaluated the safety and outcomes of this novel trabeculectomy technique, by reviewing the files
of 56 eyes of the 53 patients who underwent this surgery between February and December 2003. IOP was logged on days one to
three, weeks one to four, three months postsurgery and three times per month thereafter. Early postoperative complications
were also measured.
The day after surgery, the authors noted a decrease in IOP from 21.2 (SD 6.7) mmHg to 10.4 (SD 6.2) mmHg. Mean study follow-up
time was 15.7 months (range 12-21 months). Mitomycin C or 5-fluorouracil were applied in seven (12.5%) and two (3.6%) patients,
respectively.
Figure 2: Anterior chamber maintainer.
|
Argon suture lysis of releasable sutures and loosening or removal of adjustable sutures, performed in 21 (37.5%) and 18 (32.1%)
patients, respectively, were the two most frequent interventions resorted to during the first postoperative month in order
to lower IOP to target. Four patients (7.1%) required IOP lowering medication after trabeculectomy, and needling revision
of an inadequately filtrating bleb was necessary once in seven patients (12.5%) and twice in three patients (5.4%).
At three months postoperatively, an average IOP of 11.8 (SD 4.7) mmHg (range 4-24 mmHg) was achieved. IOP remained stable
after this period, up to one-year postsurgery, with all patients maintaining IOP levels below 21 mmHg, 61.4% of whom had an
IOP less than 14 mmHg. Mean recorded IOP at 15, 18 and 21 months was 12.8 (SD 3.1), 11.6 (SD 3.9) and 10.8 (SD 4.0) mmHg in
28, 19 and nine patients, respectively.
The most frequent postoperative complication noted during the study period was choroidal detachment, which occurred in five
patients (8.9%) at any time point. One case of endophthalmitis was reported during follow-up as well as one incident of malignant
glaucoma in a high-risk patient in the immediate postoperative period. One further incident of malignant glaucoma was reported
several months after surgery.
Is it better?
Worthy of note, however, is the excellent IOP lowering produced by this procedure, stability of IOP levels over the follow-up
period of at least 12 and up to 21 months, and the significant IOP decrease also obtained in normotensive patients.
These results do compare favourably with other major clinical studies conducted using the traditional trabeculectomy technique.6,7 Postoperative complications have, however, been found to be more frequent in some other studies.2,8–12
In summary, the authors concluded that this novel trabeculectomy technique was indeed safe and effective in establishing a
low, individually tailored and stable IOP, however, called for further trials to be conducted in order to support these findings.
Thierry Zeyen, MD, PhD is Head of the Glaucoma Unit at the University Hospital Leuven, Belgium. He may be reached by email: thierry.zeyen@uz.kuleuven.ac.be
References
1. A.P. Wells, C. Bunce, P.T. Khaw. Flap and suture manipulation after trabeculectomy with adjustable sutures: titration of
flow and intraocular pressure in guarded filtration surgery. J Glaucoma 2004; 13:400–6.
2. B. Edmunds, J.R. Thompson, J.F. Salmon, et al. The National Survey of Trabeculectomy. III. Early and late complications. Eye 2002; 16:297–303.
3. A.P. Wells, M.F. Cordeiro, C. Bunce, et al. Cystic bleb formation and related complications in limbus- versus fornix-based conjunctival flaps in pediatric and young
adult trabeculectomy with mitomycin C. Ophthalmology 2003; 110:2192–7.
4. H.W. Henderson, E. Ezra, I.E. Murdoch. Early postoperative trabeculectomy leakage: incidence, time course, severity, and
impact on surgical outcome. Br J Ophthalmol 2004; 88:626–9.
5. I. Stalmans, A. Gillis, A-S Lafaut, T. Zeyen. Safe trabeculectomy technique: long term outcome. Br J Ophthalmol 2006; 90:44-47.
6. C. Migdal, W. Gregory, R. Hitchings. Long-term functional outcome after early surgery compared with laser and medicine
in open-angle glaucoma. Ophthalmology 1994; 101:1651–6 discussion 1657.
7. The Advanced Glaucoma Intervention Study (AGIS): 7. The relationship between control of intraocular pressure and visual
field deterioration. The AGIS Investigators. Am J Ophthalmol 2000; 130:429–40.
8. P. Wilson. Trabeculectomy: long-term follow-up. Br J Ophthalmol 1977; 61:535–8.
9. K.B. Mills. Trabeculectomy: a retrospective long term follow up of 444 cases. Br J Ophthalmol 1981; 65:790–5.
10. L. Feiner, J.R. Piltz-Seymour. Collaborative Initial Glaucoma Treatment Study: a summary of results to date. Curr Opin Ophthalmol 2003; 14:106–11.
11. P. Blondeau, C.D. Phelps. Trabeculectomy vs thermosclerostomy. A randomized prospective clinical trial. Arch Ophthalmol 1981; 99:810–6.
12. M.J. Lavin, R.P. Wormald, C.S. Migdal, et al. The influence of prior therapy on the success of trabeculectomy. Arch Ophthalmol 1990; 108:1543–8.
13. M. Papadopoulos, P.T. Khaw. Improving glaucoma filtering surgery. Eye 2001; 15(Pt 2):131–2.
14. A. Feyi-Waboso, H.O. Ejere. Needling for encapsulated trabeculectomy filtering blebs. Cochrane Database Syst Rev 2004; (2):CD003658.
15. D.C. Broadway, P.A. Bloom, C. Bunce, et al. Needle revision of failing and failed trabeculectomy blebs with adjunctive 5-fluorouracil: survival analysis. Ophthalmology 2004; 111:665–73.
Novel trabeculectomy technique: the method
- A corneal traction suture was placed with a silk 8/0 and the fornix-based conjunctival flap was dissected.
- Antimetabolites were used when indicated.
- Gentle diathermy was performed.
- A 6x4 mm scleral flap with side incisions at 0.5 mm from the cornea was delineated with a 30 blade (Alcon, USA). The flap
was then dissected to half thickness with a crescent knife (Alcon).
- The central portion of the flap was dissected 1 mm into clear cornea.
- Scleral flap sutures (nylon 10/0) were pre-installed: two adjustable sutures laterally and two releasables in between.1 (Figure 1)
- An angulated site-port knife of 1.2 mm (Alcon, USA) was used to make a corneal paracentesis inferotemporally and the conic
1.3 mm Blumenthal AC maintainer (BD-Visitec, Franklin Lakes, New Jersey, USA) was positioned with the bottle of BSS (Alcon)
at 30 cm above the patient's eye. (Figure 2)
- Trabeculectomy was performed using the Khaw punch of 0.5 mm (Duckworth and Kent, Hertfordshire, UK), followed by an iridectomy.
- Flap sutures were closed (the two adjustables at the corners of the scleral flap with four throws and the two releasables
buried in between).
- Based on the flow through the AC maintainer, flap sutures were loosened, removed, tightened or added.
- According to previous studies, a flow rate of one drop every 3–4 seconds was expected to result in an IOP of 10–15 mmHg.13
- Using the "purse-string" technique, the conjunctiva was closed with two nylon 10/0 sutures. Whenever necessary additional
mattress sutures were added in between.
- In the weeks that followed, suture adjustments were made using Khaw's transconjunctival adjustable suture control forceps
(Duckworth and Kent), or removed, and/or the releasable sutures where cut with the argon laser (0.5 W, 0.1 seconds, 50 m),
according to each patient's needs, in order to reach target IOP.
- Cystic encapsulation of the bleb associated with a rise in IOP was treated by needling.14 Failing filtering blebs were treated by needling revision15 if the scleral flap was visible.
