Short-term outcomes of trabeculectomy surgery in primary open-angle glaucoma

Introduction: Trabeculectomy controls the intraocular pressure (IOP) and decreases the progress of open-angle glaucoma; the outcome of such procedure has not been ascertained in Libya. Objective: We report the short-term outcome of trabeculectomy in terms of IOP in primary open-angle glaucoma (POAG). Settings and Design: The medical records of the trabeculectomy patients previously diagnosed with POAG were reviewed retrospectively. Patients and Methods: Case characteristics were extracted including preoperative IOP and the IOP outcome 6 months postoperatively using Goldmann applanation tonometry. Data were presented as frequencies and mean ± standard deviation. Wilcoxon signed-ranks test was used to analyze the changes in the measurement of IOP after trabeculectomy. Results: Fifty-seven cases had trabeculectomy with a mean age of 51.6 ± 12.2 years. There was a statistically difference (P < 0.0001) in the IOP measurement pre and 6 months post trabeculectomy. 39 patients (68.4%) achieved an IOP of ≤21 mmHg 6 months after surgery without medications. IOP decreased from 33.2 ± 6.5 mmHg before surgery to 18.8 ± 5.8 mmHg after surgery. All the cases with preoperative IOP of 21–30 mmHg had a posttrabeculectomy IOP ≤ 21 mmHg (P < 0.0001). The rate of complications was low; seven eyes (12.3%) developed early postoperative complications that resolved within 2 weeks. Conclusions: This is the first report on trabeculectomy surgery in Libya. The results are encouraging with a low complication rate. This warrants further evaluationsof long term outcomes.

Key-words:

Intraocular pressure - Libya - primary open-angle glaucoma - trabeculectomy

Introduction

Glaucoma management is challenging, especially in low and middle income countries such as African countries.[[1]] For instance, in Libya because of the armed conflict situation, medical therapy is not available consistently and in additionthere may be delay in diagnosis due to long distances, high inflation and low income, and shortage of qualified ophthalmologists in many parts of the country.

Although trabeculectomy has been performed for patients with uncontrolled primary open-angle glaucoma (POAG) all over the regions of Libya, its outcomes and success rate had not been evaluated hitherto. The objective of this study was to examine the short-term outcome of trabeculectomy in terms of intraocular pressure (IOP) :and short-term complication rates in Libyan patients.

Patients and Methods

The records of trabeculectomies performed by a single experienced surgeon in private hospitals in two cities (Tobruk and Benghazi) in Libya in the period between January 2016 and December 2018 were studied retrospectively This involved 57 eyes.

The records of the patients previously diagnosed as POAG were reviewed, Data were extracted regarding age, sex, associated systemic diseases, preoperative glaucoma medications, preoperative IOP as baseline, IOP was measured after 5 months using Goldmann applanation tonometry.

The diagnosis of POAG was based on finding a characteristic excavation of the optic nerve head (glaucomatous cupping) using a slit-lamp biomicroscopy with the 90D Volk lens along with the Gonioscopy findings of the anterior chamber angle configuration. Visual field information were not included due to high proporation of non-availability.

Selection of patients

Only patients with POAG (only one eye from each patient) were included. Any other form of glaucoma, any prior glaucoma surgeries, cyclodestructive or laser trabeculoplasty were excluded. Indications for trabeculectomy were uncontrolled IOP and progression of the disease in spite of using maximum medication.

Surgical technique

A conventional trabeculectomy was done.[[2]] Regional anesthesia was administered and povidone-iodine was applied, then a fornix-based conjunctival flap and a rectangular half-thickness scleral flap were created. After cauterization of the scleral bed, the sclerotomy was performed followed by a peripheral iridectomy, and the flap was fixed with 10/0 buried sutures. Tenon and conjunctiva were sutured with watertight 8-0 Vicryl sutures and subconjunctival injections of gentamicin and dexamethasone were given at the end of the operation.

Postoperatively, antiglaucoma medications were discontinued and patients received cycloplegic eye drops (atropine twice a day), antibiotic eye drops (gentamycin four times/day), and prednisolone acetate eye drops (started frequently in the 1st week then tapered over 6 weeks).

A successful trabeculectomy was defined as a postoperative IOP of ≤21 mmHg at 6-month follow-up, without antiglaucoma treatment or reoperation for an elevated IOP.

Statistical analysis

Data are presented as frequencies and mean ± standard deviation (SD). We used the Statistical Package for the Social Sciences (SPSS version 23.0; IBM Corporation, Armonk, N.Y., USA). A nonparametric paired-samples test (Wilcoxon signed-ranks) was used to statistically analyze the changes in the measurement of IOP after trabeculectomy surgery.

Results

There were 57 eyes of 57 patients diagnosed to have POAG and underwent trabeculectomy surgery. The demographic data of the patients are presented in [[Table 1]]. The mean age was 51.6 ± 12.2 years with; 47 patients (82.5%) aged 40 years or more, and 38 patients (66.7%) had systemic diseases.

Table 1: Categorical variable case characteristics in 57 eyes

All the eyes of the patients were on topical antiglaucoma medications before surgery with 47 (82.5%) receiving two or more medications. An IOP of ≤21 mmHg 6 months after surgery was achieved in 39 patients (68.4%) without medications a successful trabeculectomy.

The continuous case characteristics in 57 eyes are shown in [[Table 2]]. The mean ± SD IOP decreased from 33.2 ± 6.5 before surgery to 18.8 ± 5.8 after surgery. [[Figure 1]] shows the preoperative versus postoperative IOP at 6 months. A Wilcoxon signed-rank test revealed a significant difference in the IOP measurement pre and 6 months post trabeculectomy (n = 57, Z = −6.572, P < 0.0001).

Table 2: Continuous case characteristics in 57 eyes

Figure 1: Scatterplot of preoperative versus postoperative intraocular pressure at 6 months. Each point represents 1 eye showing the preoperative intraocular pressure value on the X-axis and postoperative value on the Y-axis, respectively (P < 0.0001)

There were no statistical differences regarding sex, race, or age in the cases who had IOP ≤21 mmHg after trabeculectomy (39 eyes) [[Table 3]].

Table 3: Postoperative results 6 months after trabeculectomy in terms of intraocular pressure in 57 eyes

Twenty-four cases (42.1%) all of whom had a preoperative IOP of 21–30 mmHg achieved a successful trabeculectomy (IOP ≤21 mmHg) [[Table 3]]. Seven eyes (12.3%) developed early postoperative complications as listed in [[Table 4]], and all resolved within 2 weeks of the surgery.

Table 4: Postoperative complications (7 of 57 eyes)

Discussion

Glaucoma is the second leading cause of visual impairment worldwide.[[4]] Although medical therapy is the most common initial management option used by ophthalmologists to decrease the IOP, this may not be ideal for all patients due to factors like cost, poor patient compliance, side effects, and the intended target IOP.[[5]]

The patients in the present report came from many areas in Libya, where anti-glaucoma drugs may not be available consistently; either due to shortage of supply or inability to purchase it due to its high cost. Also, there is a shortage of experienced ophthalmologists in remote areas, All these factors contribute to the decision-making in glaucoma surgery as a first-line choice as suggested previously.[[6]],[[7]] In contrast other studies that describe the surgery as the last option for treating patients only after medical or laser treatment has failed. This view stipulates that the surgery may be contemplated as an initial treatment only in specific cases after careful consideration.[[8]]

The differences in the definitions of success of trabeculectomy in different studies, there are varying success rates of trabeculectomy ranging from 31% to 88%.[[9]],[[10]],[[11]],[[12]]

In the present report, a successful trabeculectomy as defined above was achieved in over two thirds of cases similar to the results of Yalvac et al. who reported 66.2% sucess rate at 6 months[[13]] Our results are also similar to the success rate of 63.6% (at 20 months) for trabeculectomy in black African patients in Congo.[[14]]

On the other hand, our success rates are higher than those of Mermoud et al. and Saeed,[[15]],[[16]] who reported success rates of 53.5% and 59.1%, respectively, at 6 months post trabeculectomy, Their marginally low success rates could be due to the small sample size in both the groups, the older age group in the latter study or the complexity in the disease in the former study.

In contrast, our outcome results are lower than the 85% success rate reported by El Sayyad et al., which was attributed to the use of Argon laser suture lysis in the early postoperative period and adjunctive subconjunctival injections of 5-fluorouracil.[[17]]

In the present study, there was a significant reduction in the IOP measurement at 6 months post trabeculectomy comparable to previous reports.[[14]],[[18]] In our study, patients (24) with a preoperative IOP of 21–30 mmHg developed a successful surgery, while patients (13) with preoperative IOP of 31–40 mmHg had an unsuccessful surgery by IOP criteria defined above. This is in agreement with Jay an Murray who reported that the decrease in IOP pressure was directly proportional to the preoperative level at 3 months[[19]] but this is at variance from Nesaratnam et al's 3-year follow-up study suggesting that that preoperative IOP does not prophesy the trabeculectomy surgery's success. This could be due to the difference in the duration of follow-up between the three studies studies.

The complications in the present report were self-limiting and was lower than other studies ranging from 19.7% to 47%.[[21]],[[22]],[[23]] This may be due to the variation in the definitions of trabeculectomy complications in different studies. In our study, hyphema and hypotony were the most common complications similar to previous reports.[[24]]

Few hyphema may be due to cauterization of scleral bed during surgery, and low hypotony rate can be due to its lower incidence among blacks.[[25]] In addition, other studies did not specify the glaucoma type which could be considered which may contribute to the lower complication rate in our report.

The study is limited with the relaticely small sample size and location to two private hospitals. Also it is limited by lack of information about the visual field and short time of follow-up.

Conclusions

Trabeculectomy is settings like Libya as, it controls IOP with few complications. Larger and longer term studies are warranted in more sites representative of all the population.

Authors contribution

The authors conducted the study and developed the manuscript and approved its final version.

Compliance with ethical principles

Ethical approval was not required as the this was a quality improvement exercise. All patients routinely sign a consent for their data to be used anonymously in education, research and service improvemets.

Conflict of Interest

There are no conflicts of interest.

Financial support and sponsorship

Nil.

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Publication History

Received: 21 November 2020

Accepted: 13 January 2021

Article published online:
14 July 2022