Trabeculectomy remains a frequently performed glaucoma surgery to lower intraocular pressure (IOP) because of its effectiveness in treating glaucoma refractory to medical and procedural interventions.1,2 There are several variations in the surgical steps performed in a trabeculectomy; however, the overall goal remains to permit aqueous humor outflow from the anterior chamber to sub-Tenon space.2,3 The surgical effectiveness and safety of variations in technique are still debated and have included the use of antibiotics during surgery (5-fluorouracil and mitomycin C), the thickness and shape of the scleral flap, and various conjunctival flap constructions (limbus-based or fornix-based conjunctival flap) and closures.4–8
A well-functioning bleb is critical to the success of a trabeculectomy, and surgeons must balance poor aqueous outflow potentially leading to higher IOP, with excessive flow, which can lead to a number of complications including hypotony and suprachoroidal hemorrhage.9–11 The conjunctival opening and closure plays an essential role in filtration and can affect the flow of aqueous humor and resulting IOP.12 Thus, many trabeculectomy modification techniques have focused on alterations of the conjunctival steps.
Here, we examined the surgical outcomes of a modified trabeculectomy closure technique in which the conjunctiva is incised 3 to 4 mm posterior to the limbus and is reapproximated using 2 nylon sutures without a central mattress suture, burying the posterior conjunctiva under an anterior lip of conjunctiva at the limbus (Fig. 1).
MATERIALS AND METHODS
The Johns Hopkins Medicine Institutional Review Board approved all study protocol.
A retrospective chart review was conducted on patients who underwent a trabeculectomy by a single surgeon (D.S.F.) at the Wilmer Glaucoma Center of Excellence at Johns Hopkins Hospital between January 2015 and March 2017. The standard closure technique was performed between January 2015 and May 2016 and in July 2016, the surgeon transitioned to the modified closure technique. Results through March 2017 were reviewed.
It was decided a priori to exclude the first 5 modified closure procedures performed to allow for learning. Trabeculectomies performed in conjunction with cataract surgeries, patients with less than 3 months of follow-up, and patients with previous tube shunt placements were also excluded. In advance of data collection, patients with a diagnosis of uveitis and patients with previous trabeculectomies were deemed to be at high risk for trabeculectomy failure and thus were excluded from the analysis.13 Eyes that required additional IOP-lowering surgery (ie, tube shunt, cycloablative procedures) following the initial trabeculectomy were censored from analysis at the time of second surgery and recorded as failures.
Preoperative variables abstracted included: glaucoma diagnosis, IOP, lens status, glaucoma medication use, and eye surgery history. Postoperative data were recorded for each follow-up visit for up to 1 year of follow-up. Surgical and postoperative variables abstracted included: date of surgery, laterality, complications during surgery, date of follow-up visit, IOP, glaucoma medication use, suture lysis, postoperative complications, bleb needling, and need for additional surgery.
Approximately 0.1 mL of 0.4 mg/mL of Mitomycin C, an antimetabolite, was injected into the subconjunctival space in both groups to modulate wound healing and to decrease the rate of postoperative hypotony-associated complications.14 The major difference between the 2 techniques was the location of the conjunctival peritomy and the closure of the conjunctiva. In the “standard” technique, the conjunctival peritomy was initiated at the limbus as in traditional fornix-based trabeculectomies, and the conjunctiva was closed using a central 10-0 vicryl mattress suture and two 10-0 nylon wing sutures. In the “modified” technique, a conjunctival peritomy was initiated 3 to 4 mm posterior to the limbus and two 10-0 nylon sutures were used to close the conjunctiva without a central suture, leaving an anterior lip of conjunctiva at the limbus overlying the posterior conjunctiva.
We used χ2 and t tests to compare baseline demographics and clinical characteristics between individuals who had the standard trabeculectomy closure and the modified trabeculectomy closure. Univariate 2-sample t tests were used to compare differences in reduction of IOP at 3±2 months, 6±2 months, and 12±4 months; and IOP at 1±2 days, 1±1 weeks, 1 month±2 weeks, 3±2 months, 6±2 months, and 12±4 months between the 2 techniques. The Wilcoxon Mann-Whitney test was used to compare differences in the reduction of a number of glaucoma medications at 12 months between the 2 surgical groups. A χ2 test was used to compare bleb needling and a two-sample test of proportions was used to compare total number of complications. All analyses were conducted in STATA 15 (StataCorp, College Station, TX).
The demographic and clinical characteristics are described in Supplemental Table 1 (Supplemental Digital Content 1, http://links.lww.com/IJG/A255). A total of 73 eyes were included in the final analysis. Patients had an average age of 65.7±12.0 and 63.0±12.3 in the standard and modified closure groups, respectively (P>0.05). There were no differences in sex (43.2% vs. 37.9% female) and race (54.6% vs. 37.9% African American) between the standard closure group and the modified closure group, respectively (P>0.05 for all). The 2 groups also did not differ in laterality, lens status, or glaucoma diagnosis (P>0.05 for all). The modified closure group had a higher number of non-glaucoma eye surgeries including Lasik procedures and ocular muscle corrections (n=3 in modified closure group) (P=0.03).
There were no differences in reduction of IOP at 3 months (9.9±8.2 vs. 10.5±8.7 mm Hg), 6 months (10.8±9.6 vs. 10.6±8.3 mm Hg), or 12 months (12.2±8.9 vs. 10.0±9.3 mm Hg) between the standard closure group and the modified closure group, respectively (P>0.05, Table 1). Figure 2 shows the mean IOP in the 2 groups at each time point. There was a similar mean reduction in the number of glaucoma medications at 12 months in the standard and modified groups (1.2±1.5 vs. 1.0±1.1, respectively) (P>0.05). Bleb needling in the operating room was done in 9.1% of the patients who underwent standard closure and in 13.8% of the patients who underwent modified closure (P>0.05). In the standard closure group, 2 individuals required additional IOP-lowering surgery, whereas no individuals in the modified closure group required additional IOP-lowering surgery (P=0.3). There were similar rates of complications in the standard closure group compared with the modified closure group (25.0% vs. 17.2%, P>0.05). The occurrence of each complication is detailed in Supplemental Table 1 (Supplemental Digital Content 1, http://links.lww.com/IJG/A255).
In this retrospective review, we found no differences in postoperative IOP, glaucoma medication use or postoperative complications between individuals who underwent standard closure trabeculectomies and modified closure trabeculectomies. We observed a slightly higher rate of bleb needling with the modified technique, but this was not statistically significant. We also noted fewer eyes with complications using the modified technique (25% vs. 17%), however, this difference was not statistically significant.
The key steps to the modified technique included leaving an anterior conjunctival lip, avoidance of overstretching the posterior conjunctival edge to preserve conjunctival elasticity, and tucking the conjunctiva anteriorly with the use of 2 sutures. This technique may allow for fewer bleb leaks because of increased water tightness and a better filtering bleb allowing for more aqueous outflow. In addition, although data were not collected on the surgical time, the modified technique was subjectively easier to perform and took less time than the standard technique due to more rapid access to the surgical field. Given that the conjunctiva is incised posterior to Tenon’s in the modified technique, Tenon’s capsule is less of a surgical barrier than in the standard technique. The conjunctival incision in the modified technique may also be advantageous in eyes with scarring near the limbus or with very thin conjunctiva near the limbus. Data were not recorded on the appearance of the blebs following the 2 techniques, however, blebs formed using the modified technique seemed more diffuse in comparison with the blebs formed using the standard technique.
This study is a retrospective comparison of 2 approaches to incising and closing the conjunctiva during trabeculectomy and has several limitations. First, the total number of patients studied was small, limiting our ability to detect differences in surgical outcomes between the 2 techniques. Second, a standardized protocol was not used to assess for postoperative leaks, thus, there may have been some variability in the detection of leaks. There were similar rates of leaks and hypotony in the 2 groups. Third, the number of postsurgical complications for each technique was reported; however, this measurement does not fully capture the severity of complications. Fourth, there is a potential learning curve to the modified closure technique as has been reported for various ophthalmic procedures and surgeries.15,16 However, the number of cases required to effectively learn the modified technique described is unclear. A priori, we decided to exclude the first 5 eyes with the modified closure technique to account for a potential learning curve. Fifth, data were not collected on surgical time or on the appearance of blebs following the trabeculectomy, limiting our ability to actively compare these 2 surgical/postsurgical parameters between the 2 techniques. Sixth, the surgeon doing the procedures also trains fellows and they may have done part or all of some cases using both techniques; we do not record the number of fellow contributors to a given case and therefore cannot quantify this. That said, it is likely that fellows contributed equally to both surgical approaches.
In conclusion, our study found similar surgical outcomes between a modified trabeculectomy technique and the standard technique. Results were similar, but the modified technique had fewer complications (although not statistically significant). Further studies with larger sample sizes, the inclusion of more surgeon results, and longer follow-up periods comparing the 2 techniques are warranted to more accurately compare the surgical efficacy of the modified trabeculectomy closure technique to the standard trabeculectomy technique. Future studies are also needed to compare other surgical parameters such as ease of technique, surgical time, and the learning curve between the 2 techniques.
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glaucoma; trabeculectomy; filtering glaucoma surgery
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