Liang, Yuan B. MD, PhD*,†,‡; Feng, Mei Y. MD*,†; Meng, Hai L. MD§; Fan, Su J. MD∥; Wang, Xing MD¶; Xie, Li L. MD#; Yi, Peng MSc‡; Tang, Xin MD*,†; Wang, Ning L. MD, PhD*,†; Thomas, Ravi MD**
Trabeculectomy is the most commonly performed drainage operation for glaucoma and produces fewer postoperative complications than full-thickness filtering procedures.1–4 During trabeculectomy, the surgeon attempts to achieve adequate aqueous outflow while avoiding postoperative complications such as hypotony, anterior chamber (AC) shallowing, choroidal detachment, and hypotensive maculopathy. Laser suture lysis5–9 and various techniques of releasable suture have been utilized to achieve this objective.10–17
One small randomized study examined the efficacy of releasable suture in primary open-angle glaucoma (POAG) and observed that final intraocular pressure (IOP) was controlled (≤21 mm Hg) in all 15 patients in the group with releasable sutures, and 12/15 patients (80%) in the group without releasable sutures. The releasable suture group had fewer shallow ACs and hypotony.18
Primary angle-closure glaucoma (PACG) is the major type of primary glaucoma in China,19–21 and is believed to have a higher rate of postoperative complications compared with POAG.19–22 Lasers are not readily available to many service providers in China and a survey reported that 43% of the Chinese ophthalmologists performed releasable sutures with trabeculectomy for PACG as a routine.23 Suture release was however necessary in about 40% of cases undergoing surgery.16,24 To the best of our knowledge there are no randomized trial examining the efficacy of releasable sutures when used with primary trabeculectomy for PACG.
This prospective, randomized study was performed to compare the early complications and short-term efficacy of IOP control in Chinese patients with PACG undergoing trabeculectomy with or without releasable suture.
PARTICIPANTS AND METHODS
The study (registered ChiCTR-TCR-00000218) was conducted in 4 clinical collaborative centers of the Tongren Eye Hospital: the Handan Third Hospital (Hebei Province, China); the Anyang Eye Hospital (Henan Province, China); the Fushun Eye Hospital (Liaoning Province, China); and the Chenzhou Eye and Optometry Center (Hunan Province, China). The primary purpose was to compare the short-term efficacy (and early complications) of trabeculectomy with or without releasable sutures in eyes with PACG. The tenets of the Declaration of Helsinki were adhered to and the study was approved by the ethics committee of the Tongren Eye Center, Capital Medical University. Written informed consent was obtained from all subjects.
PACG was defined as primary angle closure with the presence of glaucomatous optic neuropathy and corresponding visual field defects.25,26 Eligible subjects were recruited from the 4 centers between April 2006 and November 2007.
1. Age less than or equal to 40 years.
2. Peripheral anterior synechia in 6 clock-hours or more of the angle.
3. IOP≥21 mm Hg.
4. Evidence of optic nerve damage with cup:disc ratio ≥0.7, and/or asymmetry of cup:disc ratio ≥0.2, and/or visible retinal nerve fiber layer defect, and/or rim:disc ratio <0.1.
5. Corresponding glaucomatous visual field defect on automated perimetry.
6. Axial length ≥21 mm.
Eligible patients were required to meet all inclusion criteria.
1. Secondary angle closure.
2. History of previous intraocular surgery or trauma.
3. Patients with serious systemic diseases or family issues that could preclude follow-up.
4. Unwillingness to participate.
Before treatment all patients underwent a comprehensive ophthalmic examination including refraction, slit lamp biomicroscopy, Goldmann applanation tonometry, static and dynamic gonioscopy (using a Goldmann type 1 mirror lens) fundus examination, and automated perimeter (Humphrey Field Analyzer 750i, SITA Fast strategy, 24-2 program, or Oculus Centerfield Type 56950). Visual acuity, IOP, slit lamp examination, and an undilated examination of the disc and macula (direct ophthalmoscopy or 90 D lens) were performed on postoperative day 1, 3,7, 2 weeks, 4 weeks, and 3 months. Additional visits were scheduled if indicated. Use of additional medications, complications, and interventions were recorded.
Surgery was performed under topical or peribulbar anesthesia using a standard surgical technique. The eye was prepared using standard aseptic technique and draped to isolate the lashes. A lid speculum was inserted and a 7/0 superior rectus muscle traction suture was placed for ocular stabilization. A limbus-based conjuctival flap was created using a 10-mm incision through conjunctiva and Tenon capsule approximately 8 to 10 mm from the limbus and the flap was dissected forwards. Hemostasis was achieved by monopolar diathermy.
A half thickness 4×3 mm2 rectangular scleral flap was then fashioned. Cellulose sponges soaked in mitomycin C at a concentration of 0.3 mg/mL were then applied under the scleral flap, conjunctiva, and Tenons capsule for a duration determined by the surgeons based on assessment of risk factors. Copious irrigation with balanced salt solution was performed to wash out any residual mitomycin C solution. A paracentesis was performed, a 2×1.5 mm trabeculectomy block excised and an iridectomy performed.
In the S group, two 10/0 nylon fixed sutures were placed at the posterior corners closing the sclera flap. Tension on the individual sutures was adjusted to allow an ooze of aqueous without shallowing of the AC. In the R group in addition to the fixed sutures, 2 releasable sutures were placed at 2 sides of the flap27 (Fig. 1).
The conjunctival incision was closed with a single running 8/0 vicryl suture. Integrity of wound closure was checked by irrigating the AC with balanced salt solution and a subconjunctival injection of 2.5 mg Dexamethasone was administered. Releasable sutures were removed at the discretion of the treating surgeon, generally with an IOP increased in to the high teens (or above) with a well-formed AC. The first suture was usually removed within 2 weeks; both sutures were not removed on the same day. The first suture was released at a median of 7 days (range, 2 to 24 d), the second suture was released at a median of 13 days (range, 2 to 56 d).
Uncorrected visual acuity (UCVA) was tested monocularly using a Logarithmic VA Chart (Precision Vision, La Salle, IL) at a distance of 4 m. Those who could not read any letters at 4 m were tested at 1 m allowing for the measurement of acuities as low as 1/40 (0.025); finger counting, hand movement, light perception, were assigned an acuity of as 1.7 log MAR (20/1000), 1.875 log MAR (20/1500), 1.9 log MAR (20/1600), respectively.
A trained clinical technician using applanation tonometry performed IOP measurements. If the difference between 2 measurements was more than 2 mm Hg, a third measurement was performed and the median of the results was recorded. Hypotony was defined as IOP≤5 mm Hg.
Shallow AC was categorized as: grade I=peripheral iris-cornea touch; grade II=mid-iris to cornea touch; grade III=central cornea-lens touch.28 Postoperative subjective symptoms of foreign body sensation, tearing, blurred vision, ocular pain were recorded by an ophthalmologist using an open-ended questionnaire. Masking was not attempted.
Randomization and Statistical Analysis
A sequence for random allocation was created using SPSS statistical software. The sequence was available only to the research assistant or research nurse in the clinical center. At each site eligible patients were assigned into R or S group: the S group received standard trabeculectomy and those in R group received trabeculectomy with releasable sutures.
Sample size calculations were based on expected rates of shallow AC, 40% with standard trabeculectomy group, and 25% in trabeculectomy with releasable suture group,29 α=0.05 and β=0.20. The estimated sample size was 73 eyes in each group; anticipating a 20% loss to follow-up we planned to enroll 90 patients in each group.
Statistical analysis was carried out with SPSS v15.0. Baseline variables were compared using the χ2 test for categorical variables and t test for continuous variables. Post op IOPs between 2 groups were compared using the t test (Bonferroni corrections were used). The χ2 test was used to compare the frequency of complications in the 2 groups. P values <0.05 were considered statistically significant.
A total of 195 participants were screened. One patient did not meet the inclusion criteria and 19 declined to participate. The remaining 175 patients were randomly allocated to the R or S group. By 3 months postoperatively, 1 patient was lost to follow-up in R group and 3 were lost to follow-up in S group.
With exception of uncorrected VA demographic and clinical features at baseline: sex, age, pretreatment IOP, number of medications before surgery, spherical equivalent, visual field defect (mean deviation), and extent of peripheral anterior synechia were comparable in the 2 groups (Table 1).
The IOP in the first week after trabeculectomy was significantly higher in the R group: day 1, 17.3±8.6 versus 12.7±6.0 mm Hg (P<0.001); day 3, 18.0±7.3 versus 12.9±6.3 mm Hg (P<0.001), and day 7, 14.8±6.3 versus 12.0±4.9 mm Hg (P=0.001). No difference was observed in mean IOPs after the second week (P=0.659 to 0.753) (Table 2).
The occurrence of hypotony (20.4%) was higher in S group than the 9.1% in the R group (P<0.046). Hypotony resolved in 21 of the 26 patients (80.7%) by 1 week, and 4 cases (15.4%) resolved within 1 month. One case (3.8%) in the R group persisted beyond 1 month. The incidence of shallow AC, choroidal detachment, macular edema, additional surgery, or hyphema was not different in the 2 groups (Table 3).
In the S group, the mean UCVA was 0.73 log MAR prior surgery, 0.69 on the first day after trabeculectomy, and improved gradually by about 0.1 log MAR unit per week over 2 weeks. In the R group, the mean UCVA was 0.53 log MAR prior surgery, decreased by 0.13 log MAR unit on day 1, and then recovered to baseline level by day 7 (Fig. 2). At the end of third month the proportion of patients with ≥0.2 log MAR decrease in UCVA was more frequent in R group (18.4%, 16/87) than in S group (8.3%, 7/84), a difference of 10.1% (95% CI, 0.0%-20.1%; P=0.054). Decrease in best corrected visual acuity of 0.2 log MAR was seen in 12.6% (11/87) in R group and 2.4% (2/84) in the S group. The difference was 10.2% (95% CI, 2.6%-18.0%; P=0.011).
Foreign body sensation (36.9%), tearing (10.8%), blurred vision (6.3%), and ocular pain (2.8%) were the major complaints reported by patients on the first postoperative day. At each visit during the first postoperative month, the frequency of complaints in R group was higher than S group (Table 4).
In this randomized trial of trabeculectomy in patients with PACG using the described technique, we found no difference in IOP outcomes between the releasable and standard suture groups. Also, with the exception of transient hypotony, the incidence of early complications in the R group was comparable with S group. Patients undergoing the releasable suture technique were however more symptomatic and had a greater decrease in visual acuity.
The primary goal of releasable suture is to avoid complications such as shallow AC and hypotony in the immediate postoperative period.12,13,16–18 We found the incidence of shallow AC to be similar in the 2 groups (12.6% in R group and 13.5% in S group). For trabeculectomy performed for POAG Kolker et al12 reported 14.4% shallow ACs with releasable sutures and 32.8% in the control group. Liang et al29 reviewed 408 eyes of 329 cases with primary glaucoma (POAG:PACG=182:226) undergoing trabeculectomy with or without releasable suture between 1990 and 2000 in Zhongshan Ophthalmic Center in China. They reported the rate of any shallow AC to be 40% in the control group compared with 25% in the releasable suture group. In a randomized controlled study, in which shallow AC was defined as central AC ≤1 mm, Raina and Tuli18 found that 33% of the cases without releasable suture experienced shallow AC compared with 7% of those with releasable suture. The reported frequency of shallow AC with releasable sutures seems similar to our study but the occurrence in those undergoing standard surgery was higher (30% to 40% vs. 13.5%).
There are several possible explanations for these differences. We did not perform releasable sutures instead of, but in addition to standard sutures. In this situation we would not expect IOPs to be lower than the S group. Some previous studies included patients with acute angle closure, a condition known to having a higher rate of shallow AC after trabeculectomy.22,30 Also we excluded those with axial length <21 mm; cases which we feel are more likely to develop shallow AC. Intraoperatively we observed the eye for a few minutes after achieving equilibrium and ensured that the AC did not shallow. We feel that this also contributed to the relatively higher first day postoperative IOPs (12.7±6.0 mm Hg in the standard group and 17.3 mm Hg in releasable suture group) compared with 4.4±3.9 mm Hg in the standard trabeculectomy group and 9.0±7.9 mm Hg in releasable suture group reported by Kolker et al.12
In the present study, the rate of choroidal detachment was similar in both groups (around 3%). Liang and colleagues reported a rate of choroidal detachment of 7.1% in control group compared with the 3.3% in releasable suture group whereas Raina’s only case of choroidal detachment occurred in the control group. Stability and initially higher IOPs in our patients are probably responsible for the low choroidal detachment rate.
We defined hypotony as IOP<5 mm Hg and observed a higher rate in S group (20.4%) than in R group (9.1%). This is very similar to the 22% in the control and 9.4% in the releasable suture group reported by Liang. Hypotony is not always accompanied by maculopathy or choroidal detachment.31,32 Hypotony maculopathy after filtering surgery has been reported to occur in 1.3% to 14% of cases.33 In Liang’s report, hypotonic mauclopathy occurred in 2.2% in standard trabeculectomy group, but not in the releasable suture group. Hypotony maculopathy occurred in 2.3% in both groups, similar to 1.3% reported in a larger study (1.3%). The lower rates might be attributed to the awareness of possible hypotony with resultant adjustments in surgical techniques to reduce maculopathy.34
At the 3-month follow-up, IOP in the releasable suture group was not lower than that in the control group. Although others have found better IOP lowering with releasable sutures,18,35 our finding is consistent with a previous report.12
Some degree of vision loss after trabeculectomy has been reported in 14.9% to 33% of patients.30,36–38 Reduction of vision was more frequent in our R group. VA decreased significantly from baseline in the first week but recovered and stabilized after 1 week in R group. In the S group the vision gradually improved by 0.1 log MAR compared with baseline over the first 2 weeks. Aykan et al39 observed decreased visual acuity in 14.3% of the releasable suture group compared with 7.5% in standard trabeculectomy group. The decrease in vision with releasable sutures was probably caused by astigmatism.40
Patients in the R group also had more complaints than those who underwent a standard procedure. This could be because of the knot of the releasable suture placed at the peripheral cornea. However, up to 35% of patients in the standard group also reported discomfort. Trabeculectomy does cause a disturbance of ocular surface structure and microenvironment and41–43 both groups would share the bleb-related discomfort.
Although this was a prospective randomized study with a reasonable sample size, it does have several limitations. Firstly, despite randomization, baseline of UCVA was different in the 2 groups. However, our use of change of vision as the outcome, this would have helped adjust for the difference of baseline UCVA between the two groups. Next, as UBM ultrasound scan and OCT were not routine the rate of choroidal detachment and macular edema may have been underestimated. Finally, we excluded those with shorter axial lengths, which may have masked the protective effect of releasable suture in PACG.
In summary this prospective controlled study did not find significant advantages for this particular technique of releasable suture augmented trabeculectomy for Chinese patients with PACG. Releasable sutures increased the frequency of early VA loss and discomfort. A different technique of releasable sutures may have advantages and may be indicated in a high-risk population.
The authors thank Prof. Youqin Jiang, Zhongnan University and Prof. Tiancai Ye, Zhongshan University for contributing to develop the protocol of this study and trained the surgeons from the studied centers. The authors also thank Xuxing Wei, president of the Anyang Eye Hospital, Mingtang Li, the president of the Handan Eye Hospital, Cong Xie, the president of the Fushun Eye Hospital, Zhengqing Wu, the president of the Chenzhou Eye and Optometry Hospital for their supports with space and other necessities.
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