Abstract
Purpose
To report the visual and surgical outcomes of mitomycin-C (MMC) augmented non-penetrating deep sclerectomy (NPDS) and phacoemulsification in patients with severe and end-stage glaucoma.
Materials and methods
A retrospective analysis of 349 eyes of 320 patients who underwent combined NPDS with phacoemulsification surgery between January 2018 to December 2020 were included.
Main outcome measures
Best corrected visual acuity (BCVA), status of central visual fields, intra ocular pressure (IOP), number of antiglaucoma medications (AGM) were compared from baseline to post-operative visits, surgical complications and interventions were noted.
Results
Mean logMAR BCVA improved significantly from baseline of 0.54 ± 0.42 to 0.30 ± 0.37 & 0.29 ± 0.40 at 6(p < 0.001) & 12 months (p < 0.001) postoperatively. HFA 10-2 analysis revealed no significant post operative change in mean deviation from baseline at 6 & 12 months (p = 0.072, p = 0.143) respectively. Significant post-operative reduction in mean (SD) IOP was noted from baseline of 17.54(5.43) mmHg to 15.10(5.34) & 16.23(6.87) mmHg at 6 months(p < 0.001) and one year(p < 0.001) respectively. Similarly, the need for AGM also reduced significantly from 2.95(1.01) to 1.93(0.98) & 2.01 (0.99) at 6 (p < 0.001)& 12 months(p < 0.001) postoperatively. Cumulative surgical success was 95% and 93% at 6 months and 1 year respectively. Complications were seen in 17.8% patients and most were related to poor IOP control (8.3%). Two (0.6%) patients underwent tube surgery and 3 (0.9%) had undergone diode laser cyclophotocoagulation for refractory high IOP.
Conclusion
MMC augmented NPDS combined with phacoemulsification surgery is a safe and a viable option in eyes with advanced glaucoma maintaining stable visual acuity and visual fields postoperatively.
Subject terms: Glaucoma, Optic nerve diseases, Education
Introduction
Presentation with advanced glaucoma and severe visual field loss is a significant risk factor for lifetime blindness. Lowering intraocular pressure (IOP) is of paramount importance in reducing disease progression, especially in patients with advanced glaucoma [1–3]. Management of these patients requires disproportionally more resources than those with earlier disease. The goal of glaucoma filtering surgery is to prevent further progress of optic nerve damage, thus halting visual field loss and maintaining central vision. The advanced glaucoma intervention study (AGIS) showed that by lowering the IOP, the degradation of visual fields is reduced in these patients [4].
Significant lowering of intraocular pressure is an absolute necessity in cases of severe and end-stage glaucoma that frequently requires surgical intervention albeit the risk of loss of central vision. The treatment of advanced glaucoma study (TAGS) has shown no significant difference in the rate of progression between the medication group versus early trabeculectomy in patients with advanced visual field loss [5]. Trabeculectomy however is prone to develop potential vision-threatening complications with the use of antifibrotics including hypotony and endophthalmitis [6]. To reduce the risk of sight threatening complications, several surgical procedures such as glaucoma drainage devices, deep sclerectomy and microinvasive glaucoma surgeries have been proposed as viable alternatives to the augmented trabeculectomy [7–9].
In patients with advanced glaucoma and split fixation in central 10 degrees, one would be reluctant to perform any incisional surgery for fear of macular “snuff-out or wipe-out” phenomenon [10]. Wipe-out phenomenon is an irreversible immediate unexplained sudden loss of vision after incisional glaucoma surgery particularly in eyes with advanced glaucoma [11]. Previously, macular wipe-out was reported in 0–13.6% in eyes with advanced visual field loss with invasive glaucoma surgeries [11]. However, the loss of central vision after trabeculectomy cannot be solely attributed to wipe-out alone. Studies have shown that loss of central vision could be due to glaucoma progression, comorbidity or the procedure itself [11].
Non penetrating deep sclerectomy (NPDS) is an ab-externo filtering procedure that promotes an enhancement of aqueous outflow without penetrating the anterior chamber, thereby avoiding hypotony related complications [12–14]. Earlier reports comparing NPDS to trabeculectomy have shown fewer complications with NPDS namely flat anterior chamber, hyphaema, choroidal effusion and cataract [8, 12, 13].
Similar to trabeculectomy, there exists a lot of variations in the NPDS surgical techniques like use of antimetabolites, use of collagen matrix and postoperative management [14–17]. Earlier studies on mitomycin-C (MMC)augmented NPDS had shown higher success rate and lower long-term IOP control than those not using MMC [14, 16] The aim of our study was to primarily report the visual outcomes, postoperative visual field and surgical outcomes of MMC augmented NPDS combined with phacoemulsification in patients with co-existing cataract and severe end-stage glaucoma. The results of our study could throw light on the safe surgical management in advanced glaucoma.
Materials & methods
We retrospectively reviewed records of 459 patients who underwent MMC augmented NPDS combined with phacoemulsification surgery between January 2018 to December 2022 at a tertiary eye care centre in India. Amongst them, we selected 349 eyes of 324 patients with severe or end-stage open angle glaucoma and angle closure glaucoma with gonioscopically open superior angles and visually significant cataract. We obtained the approval of the Institutional Review Board (RET202300438) and collected the data.
We included patients with available records of Humphrey visual field analysis (HVFA)10-2 strategy showing severe glaucomatous field defect. Severe glaucoma (stage 4) was defined by a mean deviation (MD) ≤ 20 dB on the preoperative HVFA 24-2 test, with≥ 2 points within the central 5° with sensitivity of 0 dB in 10-2 test. End-stage glaucoma was defined by the inability of patients to perform HVFA 24-2 field test as a result of severe visual field loss or by a visual acuity <20/200 due to glaucoma, according to the Bascom Palmer Modified Glaucoma Staging System [18]. All eyes had a constricted visual field < 10° (severe visual field damage on HVFA 10-2) or only a central island of vision, and /or most of the HVFA 24-2 points had no (0 dB) or less than 5 dB sensitivity. Wipe-out was defined as an early and permanent reduction of postoperative visual acuity to less than 20/200 (Snellen equivalent –6/60) and to counting fingers or less if visual acuity was initially 20/400 (Snellen equivalent-1/60) [19].
Patients with a visual acuity too poor to undergo HVFA or those with corneal opacities and macular pathologies were excluded. Seven patients who had intra-operative complications such as trabeculo-descement membrane (TDM) perforation, premature entry and flap related complications that necessitated us to defer NPDS and proceed with either trabeculectomy or phacoemulsification were also excluded from our study. Patients with previous history of trabeculectomies or other intraocular surgeries were excluded.
Preoperative examinations consisted of best corrected visual acuity (BCVA), Goldmann applanation tonometry, and slit-lamp examination, including the fundus evaluation for vertical cup-disc ratio, gonioscopy, and HVFA 24-2 & 10-2 programme. These elements were recorded during the last visit before surgery. All visual field measurements were performed using the threshold automated perimetry SITA-standard 24-2 and SITA-fast 10-2 programmes, with stimulus III-White (Humphrey Field Analyzer; Carl Zeiss Meditec, Dublin, CA, USA). Only patients with reliable HVFA results were included (fixation losses and false-positive responses <20%). We did not consider false-negative responses as a criterion to characterize unreliable visual field. An increase of false-negative responses was associated with the severity of glaucoma and not with unreliability [20].
Surgical method
The procedure consisted of MMC augmented NPDS combined with phacoemulsification. All procedures have been done by the same team (four surgeons with more than 10 years of experience). The steps of the NPDS procedure were as follows: Under sub-tenon anaesthesia (3 ml of 2% Lignocaine hydrochloride +1:200000 Adrenaline Bitartrate + 750U hyaluronidase), after placing a corneal traction suture (8-0 vicryl, Aurolab, Madurai, India), subconjunctival MMC (0.04 mg/ml) was injected 8–9 mm posterior to the limbus, away from the superior rectus muscle. Then, a fornix based conjunctival flap was made and tenon dissection was done. After a light cautery over the sclera, a 5 × 4.5 mm superficial rectangular scleral flap of uniform depth of 1/3 scleral thickness was raised and dissection continued until a clear cornea was reached anteriorly. Then 4 × 4 mm deeper scleral rectangular flap was raised deroofing TDM window exposing the Schlemm’s canal and external trabeculum, and the deeper scleral flap was resected at the limbus. Ideally, the deeper scleral flap should be thicker than the superficial flap. The seepage of aqueous humour through the deroofed Schlemm’s canal was considered as the end point and a dispersive viscoelastic (Viscoat, Alcon) was used to maintain the intrascleral space. Subsequently, the superficial scleral flap was reposited and sutured to the bed of sclera using 10-0 nylon sutures (Aurolon, Aurolab, Madurai, India) on the two edges of the flap. Conjunctival flap was sutured watertight using 8-0 vicryl (Polycryl, Aurolab, Madurai, India). After this, the surgeon shifts temporally and performs the clear corneal phacoemulsification cataract surgery with foldable intraocular lens (Alcon/infinity /centurion) and the tunnel was closed with a single 10-0 nylon suture. Immediately after the surgery, patients were administered a drop of povidone iodine solution and a drop of antibiotic eyedrops (Ofloxacin 0.3%). Details of intraoperative and postoperative complications were noted. Postoperative management included a combination of antibiotic-steroid drops (Gatifloxacin 0.5% + Prednisolone acetate 1%) on a tapered schedule over a period of 12 weeks and cycloplegics (Homatropine hydrobromide 2%) for a period of 4 weeks.
Bleb morphology assessment was done by Indiana bleb appearance grading system (IBAGS) [21]. Post operative manoeuvres to enhance filtration, included Laser goniopuncture (LGP), bleb needling with antimetabolites, and restarting AGM as per surgeon’s discretion on an individual basis when filtration was judged to be inadequate or the IOP was above target. No standard criteria to perform LGP and bleb needling were set in advance, but the following general principles were followed. LGP was performed when the TDM filtration was considered inadequate and the IOP was higher than patient’s target IOP. If IOP remained out of target even after LGP, or in cases of bleb encapsulation, bleb needling augmented with MMC was performed [22–27].
LGP was performed under topical anaesthesia (lignocaine eyedrops) and in small pupils using pilocarpine eyedrops using neodymium:yttrium aluminium garnet laser (Nd:YAG) with energy levels ranging between 2 and 6 mJ with a Magna View lens (Ocular Instruments) aiming to the anterior edge of the TDM [22].
All patients were examined on day 1, 2 weeks, 1, 3, and 6 months after the procedure and every 6 months thereafter. The incidence of postoperative complications (such as flat or shallow anterior chamber, choroidal detachment, and bleb leak) and any interventions like LGP and bleb needling were recorded at each visit.
Primary outcome measures
The main outcome measures of our study were BCVA, stability of post operative visual fields on 10-2 HFA, number of intra and postoperative complications, additional interventions for IOP control and the occurrence of wipe-out phenomenon (if postoperative vision loss was not corresponding to any cause). Surgical success was primarily based on post operative visual acuity with no more than two lines drop from pre-op baseline in Snellen chart and /or wipe out phenomenon, stability of post operative visual fields with not more than 1 dB decrease in postoperative mean deviation from the baseline value, without any new areas of scotomas or deepening of the existing scotomas on 10-2 HFA (Criteria 1).
Secondary outcome measures
Secondary outcome measures were based on IOP control and need for AGM post-operatively. In our study, criteria 2 defines the complete and qualified success as IOP < 18 mmHg or 30% reduction from the baseline value with or without AGM respectively. Similarly, criteria 3 defines the complete and qualified success as IOP < 15 mmHg or 40% reduction from the baseline value with or without AGM respectively.
Failure was defined as not able to achieve the above criteria or occurrence of vision threatening complication or need for repeat surgical intervention to control IOP. Any complications which resulted in more than 2 lines loss in visual acuity for 2 consecutive visits were termed as vision threatening complication. Postoperative manoeuvres, including LGP and bleb needling with ant-fibrotic agents, were not considered to be failures as they were routine protocols followed to improve bleb survival.
Statistical analysis
Mean (standard deviation) and median (Interquartile range), and frequency (percentage) were given for continuous and categorical variables. Shapiro Wilk test was used to access the normality of the data. Visual acuity was converted to logarithm of minimum angle of resolution (LogMAR) for all comparisons. Wilcoxon signed rank test was used to compare the outcomes between baseline and follow-up visits. Cumulative probability of success were calculated and Kaplan-Meier survival plot also plotted. P value < 0.05 was considered as statistically significant. All the analyses were done using STATA version 17.0.
Results
Baseline and demographic characteristics
A total of 349 eyes of 324 patients were analysed, and the baseline characteristics are shown in Table 1. The mean ± SD age at presentation was 63.89 ± 7.76 years. Our study included 220 (67.9%) males and 104 (32.1%) female patients. About 62.8% of patients were diagnosed with Primary open angle glaucoma (POAG), 22.1% with Pseudoexfoliation glaucoma (PXFG) and 15.2% with Primary angle closure glaucoma (PACG). About 85% of our study participants had severe glaucoma (Stage 4) and 15% had end stage glaucoma (Stage 5) according to the Bascom Palmer Modified Glaucoma Staging System. The median IQR follow up was 8 months (3–16 months).
Table 1.
Demographic details of the study participants.
| Variables | n (%) |
|---|---|
| Age (in years) | |
| Mean (SD) | 63.89 (7.76) |
| Min – Max | 41-83 |
| Gender | |
| Male | 220 (67.9) |
| Female | 104 (32.1) |
| Laterality | |
| RE | 180 (51.6) |
| LE | 169 (48.4) |
| Cup Disc Ratio | |
| 0.8–0.9 | 298 (85.4) |
| 0.95 to near | 51 (14.6) |
| Diagnosis | |
| POAG | 219 (62.8) |
| PXFG | 77 (22.1) |
| PACG | 53 (15.2) |
| Spherical equivalent (in dioptres) | |
| Mean (SD) | 1.89 (1.85) |
| Min-Max | -6.50 to -2.25 |
| Median (IQR) | -2.00 (-3.00 to -0.50) |
| Follow up duration (in months) | |
| Mean (SD) | 11.47 (11.11) |
| Min-Max | 1-59 |
| Median (IQR) | 8 (3-16) |
SD Standard deviation, IQR interquartile range, RE Right eye, LE Left eye, POAG primary open angle glaucoma, PXFG pseudoexfoliation glaucoma, PACG primary angle closure glaucoma.
Visual acuity and IOP
Supplementary file 1 shows the comparison of pre and post op clinical parameters (BCVA, HFA, IOP & AGM). There was a significant improvement in the mean logMAR BCVA at all post operative visits from baseline value (0.54 ± 0.42; p < 0.001). Final logMAR BCVA at 2 years was 0.22 ± 0.21(P = 0.001). Baseline 10-2 HFA showed a MD score of 14.49 ± 1.36 which was stabilised to 14.51 ± 1.38(p = 0.072) &14.49 ± 1.40(p = 0.143) at 6 & 12 months respectively. The mean IOP decreased significantly from 17.54 ± 5.42 mmHg preoperatively to 15.18 ± 5.20 mmHg(p < 0.001), 15.36 ± 5.52 mmHg(p < 0.001),15.11 ± 5.06 mmHg(p < 0.001) and 14.12 ± 4.44 mmHg(p < 0.001) at 1 month, 3 months, 6 months and 2 years follow-up respectively. Likewise, the mean number of AGM also significantly decreased from 2.95 ± 1.01 at baseline to every post operative visit at 1,3,6,12 &18 months until the final visit at 24 months (1.98 ± 0.98; p < 0.001).
Bleb morphology
On assessing bleb morphology, majority of the patients had a predominantly low bleb at all points time (Supplementary file 2). Low bleb was noted in 87% and 65.8% of the patients at 6 months and 2 year respectively. Flat bleb was noted in 8.7% and 31.7% of patients at 6 months and 2 years respectively. Diffuse bleb was noted in <2% of patients till 6 months follow up. Less than 4% of patients had vascularised bleb at each follow up from 1 month to 18 months follow up. One patient (0.4%) alone developed tenon cyst at 3 months follow up.
Complication and re-treatment
Table 2 shows complications and additional interventions received during the study period. Posterior capsular rent was seen intraoperatively in two (0.6%) patients. The most common early post-operative complication was high IOP seen in 8.3% of the patients followed by corneal oedema in 3.7% of the patients. One (0.3%) patient each had conjunctival retraction, choroidal detachment and fibrin membrane in the anterior chamber during the early post operative period. Likewise, persistent iritis and refractory raised IOP were noted in the late post-operative period in 1.7% and 2.6% of the patients respectively. There were no cases of postoperative shallow or flat anterior chamber and postoperative endophthalmitis.
Table 2.
Complications, intervention and follow-up procedures.
| Variables | n (%) |
|---|---|
| Intra-operative complications | |
| PCR | 2 (0.6) |
| Early post-operative complications (<1 month) | |
| Corneal oedema | 13 (3.7) |
| Refractory raised IOP | 29 (8.3) |
| Conjunctival retraction | 1 (0.3) |
| CD | 1 (0.3) |
| Fibrin in AC | 1 (0.3) |
| Late post-operative complications (>1 month) | |
| Persistent iritis | 6 (1.7) |
| Refractory raised IOP | 9 (2.6) |
| Additional laser/surgical intervention | |
| AGV | 1 (0.3) |
| AADI | 1 (0.3) |
| Diode Cyclophotocoagulation | 3 (0.9) |
| Follow-up procedure | |
| Goniopuncture | 39 (11.2) |
| Bleb needling with antimetabolites | 78 (22.4) |
PCR posterior capsular rent, IOP intraocular pressure, CD choroidal detachment, AC anterior chamber, AGV Ahmed glaucoma valve, AADI Aurolab aqueous drainage implant.
A statistically significant lowering of IOP was observed in most of our patients with only 33.6% of the eyes requiring follow up procedures such as goniopuncture (11.2%) and bleb needling with antimetabolites (22.4%). As seen in Table 2, only 5 (1.5%) eyes needed additional glaucoma interventions in the form of diode cyclophotocoagulation (n = 3) and tube shunt procedures {1-non valved aurolab aqueous drainage implant (AADI) and 1- valved Ahmed glaucoma valve (AGV)}.
Success outcomes
Surgical success were analysed using three different criteria. Surgical success based on criteria 1 was about 94-95% at all follow up visits until 1 year (Table 3). Figure 1 shows the overall success rate based on criteria 1 using Kaplan-Meier analysis as 95.3% (92.1–97.2%) and 93.4% (89.7–95.8%) at 6 months and 1 year respectively. Complete success based on criteria 2 and 3 was equal to or less than 10% at all follow up visits whereas the qualified success was noted to be 72.7%, 52.2 & 74.1%, 50.5% & 74.4%, 58.3% at 6 months, 1 year and 2 years, respectively (Table 4).
Table 3.
Surgical success rate based on criteria 1*.
| Success, n (%) | Failure, n (%) | |
|---|---|---|
| 3 months (n = 301) | 283 (94.0) | 18 (6.0) |
| 6 months (n = 253) | 239 (94.5) | 14 (5.5) |
| 1 year (n = 212) | 201 (94.8) | 11 (5.2) |
*Criteria 1:
• Visual acuity with no more than 2 lines drop from pre-op baseline in Snellen chart and /or wipe out phenomenon, stability of visual fields with not more than 1 dB decrease in post-operative Mean deviation values from baseline and/or absence of any new areas of scotomas or deepening of the existing scotomas on 10-2 HFA.
• Surgical failure was based on not satisfying the above criteria or occurrence of vision threatening complication or need for repeat surgical intervention to control IOP.
Fig. 1.
Kaplan Meier curve showing overall success rate (criteria 1).
Table 4.
Success rate was given for each follow-up visit based on criteria 2* and 3#.
| Complete success, n (%) | Qualified success, n (%) | Failure, n (%) | ||||
|---|---|---|---|---|---|---|
| Criteria 2 | Criteria 3 | Criteria 2 | Criteria 3 | Criteria 2 | Criteria 3 | |
| 1 month (n = 337) | 35 (10.4) | 27 (8.0) | 207 (61.4) | 155 (45.9) | 95 (28.2) | 155 (45.9) |
| 3 months (n = 301) | 21 (7.0) | 19 (6.3) | 205 (68.1) | 150 (49.8) | 75 (24.9) | 132 (43.9) |
| 6 months (n = 253) | 11 (4.4) | 8 (3.2) | 184 (72.7) | 132 (52.2) | 58 (22.9) | 113 (44.7) |
| 1 year(n = 212) | 8 (3.8) | 7 (3.3) | 157 (74.1) | 107 (50.5) | 47 (22.2) | 98 (46.2) |
| 1.5 years (n = 202) | 9 (4.5) | 7 (3.5) | 146 (72.3) | 111 (54.9) | 47 (23.4) | 84 (41.6) |
| 2 years (n = 199) | 10 (5.0) | 10 (5.0) | 148 (74.4) | 116 (58.3) | 41 (20.6) | 73 (36.7) |
*Criteria 2:
• Complete success was defined as IOP < 18 mmHg or 30% reduction from baseline without anti-glaucoma medications.
• Qualified success was defined as IOP < 18 mmHg or 30% reduction from baseline with anti-glaucoma medications.
• Failure was defined as IOP ≥ 18 mmHg or any complications or vision deprived more than two lines.
#Criteria 3:
• Complete success was defined as IOP < 15 mmHg or 40% reduction from baseline without anti-glaucoma medications.
• Qualified success was defined as IOP < 15 mmHg or 40% reduction from baseline with anti-glaucoma medications.
• Failure was defined as IOP ≥ 15 mmHg or any complications or vision deprived more than two lines.
Discussion
We observed an overall success of 93% with combined NPDS-phaco at the end of one year with significant improvement in visual acuity, postoperative visual fields, decrease in IOP, decrease in number of AGM and minimal postoperative complications. Our study outcomes corroborated with the previous studies on NPDS in various types of glaucoma [25, 28–30]. Mercieca et al. reported an overall success rate of 89% and 80% with a IOP criteria of less than 19 mmHg & 16 mmHg respectively at a mean follow up of 63.5 ± 35.3 months [25]. In another retrospective study, it has been clearly proven that intraoperative MMC injection was associated with reduced risk of failure compared with no MMC use for both the mid-teen and low-teen IOP criteria [23, 24]. However, our failure rates at the end of two years were high (36.7%) with stringent IOP criteria of less than 15 mmHg with 58.3% of our patients requiring more than one glaucoma medications. We attribute this to the delayed scarring of the TDW and subscleral fibrosis.
About 11.5% of our study participants required LGP in their follow up period which was concordant (10%) with a study by Richardson et al. [22]. Laser goniopuncture is a vital postoperative intervention performed frequently after NPDS, ranging between 41% and 71% [26, 27]. The challenge with NPDS surgery in general is the difficulty in raising two scleral flaps without causing perforation so as to achieve an optimum thickness of TDW, thereby enhancing the aqueous outflow. In our study, we had a lower need for LGP as most surgeries were performed by experienced surgeons. Nevertheless, individual differences in the healing process could have led to subscleral fibrosis in our cohorts, requiring higher needling rates irrespective of the functioning TDW. Moreover, needling or LGP though are useful to improve the bleb survival, it can sometimes trigger or exaggerate a fibrotic response causing surgical failure [30].
In our study, we observed minimal vision threatening complications and most complication were related to raised IOP particularly in the immediate postoperative period. We would attribute this to retained viscoelastics, inflammation and steroid responder, which was managed with topical and systemic glaucoma medications. We did not encounter any episode of macular snuff out or wipe out phenomenon in any of our study participants. Few studies on trabeculectomy in advanced glaucoma have also shown no occurrence of wipe-out phenomenon [5]. However, compared to trabeculectomy, NPDS being a non-penetrating surgery, is at lower risk of developing postoperative complications like hypotony maculopathy, choroidal detachment, shallow anterior chamber, bleb erosions and vascularization, and bleb infections [31]. Compared to Rabiola et al. (5%), we only had 5(1.5%) patients requiring additional surgical interventions like diode cyclophotocoagulation and glaucoma drainage device, despite higher failure rate [30]. The rest of our patients in the failure group were put on maximal glaucoma medications and close monitoring of IOP was done. This decision was made based on patient’s visual prognosis, weighing the potential risk of additional glaucoma surgical intervention and clinician discretion.
Isolated trabeculectomy is considered to be superior to combined phaco-trabeculectomy as per previous published reports, because the combined surgery incites excessive inflammation by breaking the blood-aqueous barrier that promotes failure of the filtering bleb [32–38]. The efficacy of combined procedures like phaco trabeculectomy therefore remain controversial. However, in a recent meta-analysis on NPDS outcomes, it was reported that surgical success of NPDS was not affected, even if combined with cataract surgery [33]. We believe this to be due to the non-penetrating surgical technique, thereby mitigating the inflammatory response.
In our study, we observed stable postoperative visual fields with no change in mean deviation values from baseline. Our success based on visual field criteria was 94.8% at the end of 12 months follow up with none having a wipe-out phenomenon. Likewise, even in the TAGS on patients with advanced visual field loss, there was no difference noted in the rate of progression between the medical versus trabeculectomy [5]. However, Ates et al. in a prospective study of 54 eyes with advanced field loss (HVFA MD < -12dB) concluded that NPDS could be a valuable alternative to trabeculectomy especially in advanced open angle glaucoma [17].
Previous reports have also shown NPDS to be a safer option compared to trabeculectomy in high risk individuals as it allows the aqueous humour to percolate through the thin wall of TDM window without penetrating the anterior chamber [8, 12, 13, 15]. We believe the higher success in our study to be due to intraoperative use of antifibrotic agents, especially MMC injections.
The efficacy of NPDS in patients with PACG is still debatable with only very few reports favouring this surgical option in angle closure disease. NPDS has traditionally been avoided in eyes with pre-existing angle closure due to the possibility of the iris blocking the TDW and causing surgical failure. Similarly, efficacy of combined NPDS with cataract surgery in patients with PACG are also sparsely reported [22, 31, 32]. However Yuen et al. reported complete success of 52% and qualified success of 86% in PACG eyes after combined NPDS and cataract, without major vision-threatening complications [32]. We had only 15.2% of our study participants with diagnosis of PACG. Hence, we could not solely analyse the surgical success of NPDS in PACG.
We acknowledge limitations to this study. Firstly, we conducted a retrospective study, and the conclusions could be strengthened by a long-term prospective study and comparison with phaco trabeculectomy. Our study results may not be compared with other published studies on surgical outcomes of NPDS owing to heterogeneity in study design, type of glaucoma, severity of glaucoma, use of antimetabolites or scleral implants, success criteria and postoperative management [39–42]. Secondly, our study had a significant drop out during the follow up period. Thirdly, AS-OCT assessment of bleb morphology could not be elicited owing to retrospective study design [21]. Finally, we did not do any subgroup analysis based on different types of glaucoma since majority of our study patients were diagnosed with POAG. However, the major strength of our study is the large sample size with a mean follow up of 11.5 months. We report an overall success of 93% at 1 year that make this procedure a viable option in eyes with advanced glaucoma which are at risk of losing central vision.
Combined MMC-augmented NPDS and cataract surgery is a safe procedure in patients with severe and end stage glaucoma, without any significant vision threatening complications, with stabilisation of visual fields and improvement in central visual acuity.
Summary
What was known before?
Phaco-NPDS with MMC augmentation is effective in lowering IOP in the long-term in managing advanced glaucoma.
The procedure has a low risk of sight threatening complications.
What our study adds?
This study shows that combined NPDS and phaco is a safe and effective surgical procedure for patients with advanced and end stage glaucoma in both short and intermediate term.
Supplementary information
Author contributions
Concepts: RS, VAS. Design: RS, VAS. Definition of intellectual content: RS, TS, MR, VAS. Literature search: RS, TS, MR, JK, VAS. Clinical studies: RS, JK, KBS, VAS. Experimental studies: RS, TS. Data acquisition: TS, MR, JK. Data analysis: KBS. Statistical analysis: KBS. Manuscript preparation: RS, TS, MR, JK, VAS. Manuscript editing: RS, KBS, VAS. Manuscript review: RS, KBS, VAS. Guarantor: RS, VAS.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
The online version contains supplementary material available at 10.1038/s41433-025-03719-z.
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