The comparison of the effects of nasal and temporal approaches on surgical success in trabeculectomy and phacotrabeculectomy

Authors

Abstract

Aim Trabeculectomy is the most commonly performed surgery in glaucoma patients with progressive disease despite medical and laser treatments. The aim of this study was to evaluate the effect of surgical site in trabeculectomy on intraocular pressure and surgical success postoperatively.
Materials and Methods A total of 94 patients were included in the study (52 trabeculectomy and 42 phacotrabeculectomy). Among the trabeculectomy patients, 18 underwent nasal approach and 34 underwent temporal approach with scleral flap and iridectomy at the same quadrant. In the phacotrabeculectomy group, 21 patients underwent nasal approach, and 21 patients underwent temporal approach. The best corrected visual acuity (BCVA), intraocular pressure (IOP), and anti-glaucoma medication requirements were recorded preoperatively and postoperatively, and statistically evaluated.
Results In the trabeculectomy group, intraocular pressure initially decreased similarly in both approaches but was lower in the nasal group by the third month, though not statistically significant (p>0.05). At three months, 27.8% of the nasal group and 41.2% of the temporal group required anti-glaucoma medication, with no significant difference (p>0.05). In the phacotrabeculectomy group, nasal and temporal iridectomy were performed equally in 21 patients (50% each). By three months, intraocular pressure was lower in the temporal group, but significant differences appeared only on day one and month one (p<0.05). Medication use was similar between groups, with 57.1% of the nasal group and 47.6% of the temporal group requiring treatment (p>0.05).
Discussion In our study, there was no significant difference in intraocular pressure and anti-glaucoma medication use at the three-month follow-up in patients who underwent scleral flap and iridectomy filtering surgery via nasal and temporal approaches in both trabeculectomy and phacotrabeculectomy groups.

Keywords

Introduction

Glaucoma is an optic neuropathy caused by progressive degeneration of the optic nerve and is one of the leading causes of permanent blindness worldwide [1]. It is the second most common cause of irreversible blindness in the United Kingdom, North America, and Europe [2, 3]. The estimated prevalence of glaucoma in individuals aged 40-80 worldwide is 3.5% [4]. In all types of glaucoma, irreversible degeneration of retinal ganglion cells (RGCs) is expected as the disease progresses [5]. Glaucoma can be classified into two groups: open-angle glaucoma and angle-closure glaucoma [6]. The most important step to be taken before optic nerve damage develops in glaucoma patients is to reduce intraocular pressure, one of the risk factors. Standard methods for lowering intraocular pressure include eye drops and/or laser treatment. When these treatments are insufficient, surgical methods are used as an option [7]. Among surgical methods, trabeculectomy is the most frequently performed procedure [8]. It is considered the gold standard for patients with progressive glaucoma despite medical and laser treatment [9]. In trabeculectomy, intraocular pressure is reduced through the formation of a subconjunctival fistula [10]. The success rate of trabeculectomy in primary glaucoma has been reported to range between 67% and 94% [11]. Trabeculectomy was first described in 1968 by Cairns as being performed at the 12 o’clock position; however, it has been reported that it can be performed at any location around the corneoscleral region [12]. Previous studies have reported that nasal trabeculectomies provide better long-term intraocular pressure control [13]. The effectiveness of combined trabeculectomy and phacoemulsification in patients with open-angle glaucoma, compared to trabeculectomy alone, remains uncertain. While some studies have shown similar efficacy [14, 15], others have reported higher failure rates in patients undergoing combined procedures [16, 17, 18]. Environmental differences in the structure of the Schlemm canal and the distribution of collector channels have contributed to the variable outcomes of minimally invasive glaucoma surgery (MIGS) [19, 20]. In this study, the success rates of temporal and nasal approaches in trabeculectomy and phacotrabeculectomy procedures were evaluated, considering the environmental and anatomical differences in the aqueous humor drainage system.

Materials and Methods

A retrospective analysis was conducted on the electronic records of patients diagnosed with open-angle glaucoma who underwent trabeculectomy or phacotrabeculectomy due to an inadequate response to medical treatment at the Glaucoma Unit of the Department of Ophthalmology at Çanakkale 18 Mart University between 2019 and 2024. This study was designed as a retrospective study and followed the principles of the Helsinki Declaration. A total of 94 patients were included in the study. Patients who showed progression in visual field and failed to achieve sufficient reduction in intraocular pressure despite maximum topical anti-glaucoma therapy were included for surgery. Patients who had undergone any intraocular surgery other than phacoemulsification, as well as those with a history of trauma, ocular inflammation, or infectious ocular diseases that could affect intraocular pressure (IOP), were excluded. Additionally, all patients who developed complications were not included in the study. The best corrected visual acuity (BCVA), IOP, and anti-glaucoma medication information were recorded before surgery and during the three-month postoperative follow-up period. Both types of surgeries were performed using the same technique by the same surgeon at a single center. For the trabeculectomy procedure, a 4x4 mm partial thickness scleral flap was created at the limbus in all eyes. A 0.2 mg/ml mitomycin C was applied to the scleral bed using four sponges for 3 minutes. After being washed with saline, an iridectomy was performed. The iridectomy was done at the 2 o’clock position in patients who underwent surgery on the right eye and at the 10 o’clock position in patients who underwent surgery on the left eye. The edges of the scleral flap were closed with 10-0 nylon sutures, and the conjunctiva was closed with 8-0 vicryl sutures. In patients who underwent phacotrabeculectomy, cataract surgery was performed first, followed by the trabeculectomy procedure as described above. For all patients, IOP measurements were obtained using Goldman applanation tonometry on the first postoperative day, first week, first month, and third month. The BCVA was measured using a Snellen chart, and patients were grouped into three categories: group A (BCVA < 0.05), group B (BCVA 0.05–0.29), and group C (BCVA ≥ 0.3).
During the follow-up period, patients requiring anti-glaucoma drops were provided treatment.
Statistical Analysis
Statistical analyses were performed using Statistical Package for the Social Sciences (SPSS) version 11.0 (Chicago, IL, USA). Results are presented as mean ± standard deviation. The normality of the data distribution was assessed using the Kolmogorov-Smirnov test. Parametric or non-parametric tests were chosen based on the data distribution. Results with a p-value of less than 0.05 were considered statistically significant.
Ethical Approval
This study was conducted in accordance with the principles of the Declaration of Helsinki. As this was a retrospective study, approval from the institutional ethics committee was not required.

Results

A total of 94 patients were included in the study and followed for three months postoperatively. Of these, 52 (55.3%) underwent trabeculectomy, while 42 (44.7%) underwent phacotrabeculectomy. Among the patients who underwent trabeculectomy, 25 (48.07%) were female, and 27 (51.93%) were male. Seventeen patients (32.7%) were pseudophakic, while 35 (67.3%) were phakic. Nasal iridectomy was performed in 18 patients (34.6%), whereas 34 patients (65.4%) underwent temporal iridectomy(Table 1). In the nasal iridectomy group, 5 patients (27.8%) required postoperative anti-glaucoma medication, while 13 (72.2%) were monitored without medication. In the temporal iridectomy group, 14 patients (41.2%) were started on medication, whereas 20 (58.8%) were followed without treatment (Table 2). Complications were reported in 2 out of 52 patients—one from the nasal group and one from the temporal group. For patients who underwent trabeculectomy, the mean intraocular pressure (IOP) in the nasal iridectomy group was recorded as 23.33 mmHg preoperatively and 8.44, 9.56, 13.11, and 13.00 mmHg at postoperative first day, first week , first month , and third month , respectively. In the temporal iridectomy group, the corresponding values were 27.18, 10.7, 10.24, 14.03, and 14.57 mmHg. Although the IOP was lower in the nasal group at the third-month follow- up, the difference was not statistically significant (p>0.05) (Table 1). Regarding best corrected visual acuity (BCVA), in the nasal iridectomy group, 4 patients were classified as Group A, 4 as Group B, and 10 as Group C preoperatively. By the third-month follow-up, these numbers had changed to 3, 8, and 7, respectively. In the temporal iridectomy group, 16 patients were in Group A, 6 in Group B, and 12 in Group C preoperatively, with these numbers shifting to 17, 4, and 13, respectively, at the third month. The difference was not statistically significant between the two groups (p>0.05). Among the 42 patients who underwent phacotrabeculectomy, 29 (69%) were female, and 13 (31%) were male. All patients in this group were phakic. Nasal and temporal iridectomy were performed in equal proportions, with 21 patients (50%) in each group ( Table 1). In the nasal iridectomy group, 12 patients (57.14%) required postoperative anti-glaucoma medication, while 9 (42.9%) were monitored without medication. In the temporal group, these numbers were 10 (47.6%) and 11 (52.4%), respectively (Table 2). One complication was reported in the nasal iridectomy group. The IOP values in the nasal iridectomy group were recorded as 25.57 mmHg preoperatively and 15.38, 14.24, 16.57, and 15.43 mmHg at postoperative first day , first week, first month, and 3rd month, respectively. In the temporal iridectomy group, the corresponding values were 26.57, 10.19, 16.05, 12.95, and 13.71 mmHg. IOP was significantly lower in the temporal group on the first postoperative day and first month(p<0.05) (Table 3). Regarding BCVA, in the nasal iridectomy group, 13 patients were classified as Group A, 7 as Group B, and 1 as Group C preoperatively. By the third month, these numbers changed to 6, 3, and 12, respectively. In the temporal iridectomy group, there were 16 patients in Group A, 4 in Group B, and 1 in Group C preoperatively. By the third month, these numbers had changed to 17, 6, and 19, respectively. A statistically significant difference was not observed between the two groups (p>0.05) .

Discussion

In cases where medical treatment is insufficient for glaucoma patients, trabeculectomy surgery is the most common surgical procedure used to reduce IOP by providing drainage from the anterior chamber to the subconjunctival space. However, the success of this surgery can be limited due to postoperative fibroblast proliferation and scarring of the filtering bleb [21]. Studies examining the effect of the surgical intervention site on postoperative IOP and surgical success in trabeculectomy are limited. In this study, we aimed to evaluate the impact of the surgical site (nasal or temporal) on IOP and postoperative medication requirements in patients who underwent trabeculectomy and phacotrabeculectomy. A study by Roshani et al. in 1993 reported that patients who underwent nasal trabeculectomy had lower IOP during long-term follow-up compared to temporal and superior surgeries [13]. Cha et al.‘s study also showed that fluid drainage was more active in the nasal and inferior quadrants due to the wider trabecular meshwork and the greater connection between the collector channels and Schlemm’s canal in these areas [20]. These findings suggest that surgeries performed in these areas may be more effective in reducing IOP. In our study, when comparing nasal and temporal iridectomy groups in patients who underwent trabeculectomy, similar results were obtained for IOP reduction during the first two months postoperatively. However, at the third month, patients who underwent nasal iridectomy had lower IOP values compared to the temporal group. Although this finding suggests that nasal iridectomy may be more effective in IOP control, no statistically significant difference was observed. Following cataract surgery, IOP reduction has been observed in both glaucoma and non-glaucoma eyes [22]. In our study, in contrast to the trabeculectomy group, when comparing the nasal and temporal groups in patients who underwent phacotrabeculectomy, the temporal group had lower IOP throughout the three-month follow-up period, with statistically significant differences observed on the first postoperative day and at 1 month. However, at the third-month follow-up, although the temporal group had lower IOP, no statistically significant difference was found. The impact of the surgical site on postoperative IOP control was initially significant, but over time, this effect diminished, suggesting that the surgical site has a minimal role in IOP control during the three-month period and that other factors are more important in controlling IOP. The causes of trabeculectomy failure are generally related to intraocular, scleral, and extraocular factors [23]. A study by Seol et al. on mitomycin C (MMC) reported that both 0.2 mg/mL and 0.4 mg/mL MMC-treated groups effectively controlled IOP with low complication rates [24]. In our study, we used 0.2 mg/mL MMC in all patients to improve postoperative success. Landers et al. defined the long-term success criteria for trabeculectomy as reducing IOP to below 21 mmHg in glaucoma patients with high IOP and a 20% reduction in glaucoma patients with normal IOP [25]. Based on this reference, we observed that the nasal group had a lower need for additional medication. However, this difference was not statistically significant. In studies with a larger patient group, the likelihood of finding a statistically significant difference in the medication requirement in the nasal iridectomy group could increase. In phacotrabeculectomy patients, the medication use rates were similar between the nasal and temporal groups, with no statistically significant difference. The minimal effects of nasal and temporal iridectomy on IOP during the three-month follow-up period may have contributed to the lack of significant differences in medication use. Although the surgical site had an impact on IOP in the first months, both nasal and temporal iridectomy may yield similar results by the third month. Therefore, the difference in the need for additional medication is unlikely to be significantly related to the surgical site.To better understand the impact of the surgical site on IOP control and success rates, further studies with larger sample sizes and long-term follow-up are needed. Such studies could more clearly identify the effects of the surgical site on IOP control not only in the short term but also in the long term, and provide more reliable assessments of important clinical outcomes such as medication requirements and surgical success.

Limitations

The main limitations of this study are the small sample size and the short, three-month follow-up period, which may limit the ability to detect long-term outcomes and subtle differences between surgical approaches. Further large-scale, long-term studies are needed to confirm these findings.

Conclusion

In this study, similar effectiveness in intraocular pressure (IOP) control and medication use was observed in the short term between surgeries performed in the nasal and temporal regions in patients who underwent trabeculectomy and phacotrabeculectomy. Both surgical approaches showed similar effects on IOP and did not result in significant differences in postoperative medication use. These findings suggest that both surgical approaches are equally effective in the short term. Future studies with larger sample sizes could better evaluate the long-term effectiveness of nasal iridectomy.

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