Abstract
Background:
Neovascular glaucoma (NVG) is a secondary glaucoma with a poor visual prognosis. Trabeculectomy with antifibrotic agents, glaucoma drainage devices (GDDs), and cyclo-destructive procedures are recommended in patients who are refractory to medical management. However, due to the poor success rate of conventional trabeculectomy and the higher cost of GDDs, alternative procedures need to be looked at.
Purpose:
To compare the surgical outcomes and economic aspects of a newly developed polypropylene suture bed-based modified trabeculectomy to Ahmed glaucoma valve (AGV) implantation for NVG.
Methods:
It was a prospective interventional study conducted at a tertiary care center between 2018 and 2020. Consecutive patients with NVG with a minimum follow-up of 18 months were included. Surgical outcomes are mainly based on intraocular pressure (IOP) control and the cost of surgery.
Results:
Sixty eyes were included out of which 40 (60.6%) underwent modified trabeculectomy and 20 (33.7%) underwent AGV. At the final follow-up, no significant difference (P < 0.05) was found between the surgical outcomes of both groups. The complete success rate (IOP < 21 mm Hg without antiglaucoma medications) was 60 and 65% while the qualified success rate (IOP < 21 mm Hg with antiglaucoma medications) was 30 and 25% in modified trabeculectomy and AGV groups, respectively, at final follow-up. The cost of surgery was significantly higher in the AGV group (P < 0.0001).
Conclusion:
Modified trabeculectomy as described might be a better alternative for NVG eyes.
Keywords: Ahmed glaucoma valve, neovascular glaucoma, polypropylene-based modified trabeculectomy
Neovascular glaucoma (NVG) is a potentially devastating sequelae of serious underlying ocular and/or systemic disease with guarded visual prognosis. Proliferative diabetic retinopathy and retinal vascular occlusions are the two most important causes of NVG.
Antivascular endothelial growth factor injections (anti-VEGF) and pan-retinal photocoagulation with antiglaucoma medications are the mainstay of treatment of NVG. Trabeculectomy with antifibrotic agents, glaucoma drainage devices (GDDs), and cyclo-destructive procedures are recommended in patients who are refractory to medical management.[1] However, conventional trabeculectomy has a high rate of failure while the use of GDDs is limited due to their high cost.[2]
Thus, a new technique of polypropylene suture bed-based modified trabeculectomy was developed to address the high failure rate of conventional trabeculectomy. In this study, we aimed to evaluate the surgical outcome of polypropylene-based modified trabeculectomy in comparison to conventional shunt surgery for NVG. We also intended to compare the cost of surgery between the two procedures.
Methods
It was a prospective, interventional, institution-based study carried out between 2018 and 2020 in eastern India. The study was approved by the Institutional Review Board and adhered to the tenets of the Declaration of Helsinki for research involving human subjects. Written informed consent was obtained from all participants included in the study.
Consecutive patients with the diagnosis of NVG with intraocular pressure (IOP) not controlled on maximum medication were included in the study. Uncontrolled NVG was defined as IOP above 21 mm Hg with maximum antiglaucoma medications. Minimum follow-up required for inclusion in the data analysis was 18 months.
Patients with no light perception, with media opacities like vitreous hemorrhage, or posterior segment complications like tractional retinal detachment were excluded from the study. Extensive synechial angle closure was excluded from the study. Those with a history of previous ocular surgeries except cataract surgery were also excluded. Patients with uncontrolled diabetes or hypertension were excluded from the study.
A detailed preoperative examination was carried out for all the patients one week before the surgery. History of systemic disorders, type of glaucoma, and number of glaucoma medications used were noted. Slit lamp biomicroscopic examination, lens status, IOP measurement using Goldmann applanation tonometry, gonioscopy using a Goldmann four-mirror lens, optic disc evaluation with a Volk 90 D lens, and indirect ophthalmoscopy using a Volk 20 D lens were performed. The best-corrected visual acuity (BCVA) was measured using Snellen’s chart which was then converted to a logarithm of the reciprocal of the minimal angle of resolution log (MAR). All the surgeries were performed by a single surgeon. All patients received a single dose of intravitreal injection anti-VEGF (Ranibizumab 0.5 mg/0.05 ml) 5–7 days before glaucoma surgery and platelet-rich plasma (PRP) was done in all patients.
Patients were followed up at regular intervals on postoperative day 1, 1 month, 3 months, 6 months, 12 months, and 18 months. On each visit, BCVA and IOP were recorded. Both anterior and posterior segments of the eye were examined at each visit.
Any postoperative complication was recorded. The number of antiglaucoma medications added for IOP control post-surgery was noted at each visit. If IOP was >21 mm Hg, antiglaucoma medication was prescribed. Patients were grouped as complete success, qualified success, and failure after each visit. Complete success was defined as IOP <21 mm Hg without any antiglaucoma medication. Qualified success was defined as IOP <21 mm Hg with antiglaucoma medications. Failure was defined as (1a) IOP >21 mm Hg despite the use of maximum antiglaucoma medications. (1b) Any posterior segment complication due to surgery not due to a disease process.
Surgical technique
Peribulbar anesthesia was used in all the patients. For modified trabeculectomy with polypropylene bed-based suture, a superior corneal traction suture was placed with 8-0 vicryl. Next, a fornix-based conjunctival flap was created followed by a triangular-shaped scleral flap. Cotton pellets soaked in mitomycin C (0.04%) were placed under the conjunctiva and flap for 2 min. After that, the pellet was removed and copious irrigation was done. A polypropylene bed was made with non-absorbable, inert 8-0 polypropylene sutures.
An infero-temporal paracentesis was created. A full-thickness sclerotomy was made with punch after which a peripheral iridectomy was created at 12 o’clock position. The scleral flap was closed with 10-0 nylon sutures and the conjunctival flap was closed with 8-0 vicryl sutures [Fig. 1a-d].
Figure 1.
Schematic diagram of trabeculectomy using polypropylene. (a) Creation of triangular scleral flap, (b) “Polypropylene bed” under scleral flap with 8-0 polypropylene, (c) Creation of sclerotomy “ostium”, (d) Suturing of scleral flap with 10-0 polypropylene
For AGV implantation, the first step was priming of the device which was performed to check the integrity and patency of the valve by injecting 1cc of balanced salt solution with a 26-G cannula. A fornix-based conjunctival flap was created in the supero-temporal quadrant between two adjacent recti muscles. The implant was sutured to the sclera 8–10 mm from the limbus with 9-0 nylon and the drainage tube was trimmed to permit 2–3 mm insertion in the anterior chamber with a beveled cut at 30°. Anterior chamber paracentesis was performed and a viscoelastic substance was injected following which the anterior chamber was entered 1–3 mm posterior to the limbus with a 22-G needle parallel to the plane of the iris. The tube was entered through the needle tract with a bevel facing the corneal endothelium and then the drainage tube was covered with an amniotic membrane-umbilical cord (AM-UC) graft sutured to the sclera by 10-0 nylon. In all the patients the tube was placed in the anterior chamber. The conjunctiva was then anchored to the limbus with 8-0 vicryl sutures and subconjunctival antibiotic with steroid was injected [Fig 2b and c]. All antiglaucoma medications were stopped from postoperative day 1 and patients were followed up regularly as mentioned before.
Figure 2.
(a) Comparison between preoperative and postoperative IOP of modified trabeculectomy and AGV. (b) Comparison between preoperative and postoperative BCVA of modified trabeculectomy and AGV. (c) Kaplan-Meier analysis curve showing a comparison of the probability of complete success between modified trabeculectomy and final postoperative follow-up
Statistical methods
Statistical analysis was performed with the help of EPI INFO (TM) 7.2.2.2. EPI INFO https://www.cdc.gov/epiinfo/index.html#:~:text=interoperable%20software%20tools-,designed,-for%20the%20global is a trademark of the Centres for Disease Control and Prevention. A test of proportion was used to find the standard normal deviate (z) to compare the different proportions, the Chi-square test was used to find an association, and the t-test was used to compare the means of the two groups. P < 0.5 was taken to be statistically significant.
Results
A total of 60 eyes of 60 patients with NVG uncontrolled glaucoma medication were enrolled for the study. Forty eyes underwent modified trabeculectomy with polypropylene suture while 20 underwent Ahmed glaucoma valve (AGV) implantation (FP 7). The preoperative data for the two groups are shown in Table 1. There were no significant differences in mean age, lens status, etiology of neovascular glaucoma, preoperative intraocular pressure, number of antiglaucoma medications, and BCVA between the two groups.
Table 1.
Base parameters
| Base parameters | Modified trabeculectomy surgery (n=40) | Ahmed glaucoma valve surgery (n=20) | P |
|---|---|---|---|
| Age (in years) | |||
| Mean±S.D. | 54.00±3.23 | 53.20±2.74 | 0.59 |
| Median | 53.00 | 53.50 | |
| Range | 50–60 | 50–56 | |
| Gender | |||
| Males | 40 (100%) | 20 (100%) | 0.99 |
| Females | 0 (0.0%) | 0 (0.0%) | |
| Laterality of eye | |||
| Right eye | 28 (70.0%) | 12 (60.0%) | 0.58 |
| Left eye | 12 (30.0%) | 8 (40.0%) | 0.58 |
| Lens status | |||
| Phakic | 32 (80.0%) | 14 (70.0%) | 0.54 |
| Pseudophakic | 8 (20.0%) | 6 (30.0%) | |
| Etiology of NVG | |||
| PDR | 28 (70.0%) | 15 (75.0%) | 0.08 |
| CRVO | 12 (30.0%) | 5 (25.0%) | |
| Preoperative IOP in mm Hg (mean±S.D.) | 40.7±4.52 | 38.5±3.64 | 0.07 |
| Preoperative medications (mean±S.D.) | 3±1 | 3±1 | 0.99 |
| Preoperative visual acuity in logMAR | 1.52±0.65 | 1.54±0.58 | 0.08 |
Fig. 2a shows the mean IOP before and after surgery at each follow-up visit in both the modified trabeculectomy and the AGV groups. In both groups, the mean postoperative IOP at all follow-up time points was lower than the mean preoperative IOP. The mean IOP did not differ statistically between the two groups at any postoperative time point (P = 0.54).
Fig. 2b shows the mean logMAR vision before and after modified trabeculectomy with polypropylene and AGV implantation, with no significant differences between the two groups (P = 0.582). The mean BCVA at the final postoperative visit at 18 months was logMAR 1.49 ± 0.23 and logMAR 1.45 ± 0.36 in the modified trabeculectomy and AGV groups, respectively, which is significantly lower than that at 6 and 12 months (P = 0.003). This may be attributed to the six patients who underwent failure due to uncontrolled IOP by the end of 18 months.
The mean number of preoperative antiglaucoma medications was 3.1 ± 0.72 and 3.2 ± 0.68 while that at the final postoperative follow-up (18 months) was 1.24 ± 0.46 and 1.36 ± 0.56 in modified trabeculectomy and AGV groups, respectively. There was a significant decrease in the number of antiglaucoma medications used postoperatively at 18 months from preoperative values (P = 0.0001). However, there was no significant difference between both groups at the final follow-up (P = 0.067).
Kaplan–Meier survival curves for complete success following modified trabeculectomy and the AGV implantation are shown in Fig. 2c. There were no treatment failures in either group within the first 10 months of postoperative follow-up. The complete success rates were 80% and 80% at 12 months postoperative, and 60 and 65% at 18 months in the modified trabeculectomy and AGV groups, respectively. The failure rates were 10% for both groups at the final follow-up visit at 18 months. The difference between the survival curves was not statistically significant (P = 0.815).
A total of six eyes were classified as failures: four eyes in the modified trabeculectomy group and two eyes in the AGV group. Two eyes were successfully well managed with needling and the rest of the two were in a modified trabeculectomy group planned for future AGV. No posterior segment complications were noted due to surgery.
Postoperative complications in both groups are summarized in Table 2. Hyphema and hypotony were the two most common complications seen in the early postoperative period, occurring in four (10%) eyes in the modified trabeculectomy group and two (10%) eyes in the AGV group. Hyphema was managed medically with topical steroids, antiglaucoma medications, and cycloplegics and resolved within 3–5 days. Transient hypotony (IOP <6 mm Hg) was seen in both groups for 2–3 weeks. One patient (5%) developed cataract after 6 months postoperative and one patient (5%) had encapsulated bleb in the AGV group. There was no occurrence of a flat anterior chamber, hypotonous maculopathy, or endophthalmitis in either group. The cost of treatment in the case of modified trabeculectomy surgery was in the range of INR 802–902 (mean INR 866.10 ± 53.91) as compared to AGV surgery which was INR 15,000–16,000 (mean INR 15,500).
Table 2.
Postoperative complications
| Postoperative complications | Modified trabeculectomy (n=40) | Ahmed glaucoma valve (n=20) | P |
|---|---|---|---|
| Hyphema | 2 (5.0%) | 1 (5.0%) | 0.99 |
| Hypotony | 2 (5.0%) | 1 (5.0%) | 0.99 |
| Cataract progression | 0 (0%) | 1 (5.0%) | 0.99 |
| Encapsulated bleb | 0 (0%) | 1 (5.0%) | 0.99 |
Discussion
Eyes with NVG that do not respond to medical and laser therapy are often managed with GDDs like AGV, Baervaldet valve, or trabeculectomy with antimetabolites. Conventional trabeculectomy shows a high rate of failure in NVG.[1] The use of antifibrotic agents like mitomycin C helps to reduce the failure rate of conventional trabeculectomy. GDDs are often used as a primary surgical procedure in patients with neovascular glaucoma particularly those with severe inflammation at presentation. GDDs may be valved or non-valved. AGV has a better IOP controlling mechanism than most other valved GDDs. However, most GDDs especially AGV, are expensive and not affordable for the lower socio-economic groups. Thus, a new technique of modified trabeculectomy with polypropylene suture was developed in our institution for the treatment of refractory neovascular glaucoma to combat the high failure rates of conventional trabeculectomy and the high expense of GDDs.
Polypropylene (8-0) sutures were used to create a bed of sutures called a ‘polypropylene bed’ below the scleral flap of trabeculectomy which created a tenting of the scleral flap preventing fibrosis and facilitating aqueous outflow. The mechanical action of polypropylene sutures also helps to reduce the chances of bleb failure. The rate of suture breakage is high with the use of 10-0 polypropylene sutures but 8-0 polypropylene sutures have higher tensile strength and are inert and non-absorbable which allows them to sit stable below the scleral flap in the polypropylene bed for a long time. These properties of 8-0 polypropylene are being utilized in the scleral fixation of intraocular lens as well.[2,3] It is therefore expected that this technique of modified trabeculectomy will have lower failure rates as compared to conventional trabeculectomy in neovascular glaucoma.
Another study by Ahmed Mostafa Abdelrahman et al.[4]where they showed implantation of a 5/0 prolene suture in Schlemm’s canal during deep sclerectomy was a safe, cost-effective adjunct to maintain the patency of the intrascleral space and Schlemm’s canal thus controlling IOP for 6 months postoperatively.
In this study, we compared the surgical outcomes between the newly developed modified trabeculectomy with AGV implantation in neovascular glaucoma and found similar success rates in both groups. At 12 months, the complete success rate was 80% in both groups while at 18 months complete success rates were 60 and 65% in modified trabeculectomy and AGV groups, respectively, with no statistical difference.
Hyung et al.[5] reported a surgical success rate of 71% at 1 month and 29% at 1 year while Mandal et al.[6] reported a higher success rate of 66.7% at 1 year after trabeculectomy with mitomycin C in neovascular glaucoma. Yalvac et al.[7] reported a surgical success rate of 63.3% at 1 year of AGV implantation. Im et al.[8] in their study compared AGV implantation and trabeculectomy with mitomycin C for neovascular glaucoma. At 1 year after trabeculectomy and AGV implantation, complete success was 47.8 and 42.3% while qualified success was 30.4 and 46.2%, respectively. Shen et al.[9] conducted a similar study where at 2 years success rate of AGV was 60% and that for trabeculectomy with mitomycin C was 55% in NVG eyes. The success rate as per Kaplan-Meier analysis for both trabeculectomy and AGV implantation in our study was either similar or more than that to the findings of these studies as mentioned above.
Even then the failure rates are much lower than that given by the above-mentioned studies which may be attributed to intravitreal injection of the anti-VEGF drug ranibizumab (0.5 mg/0.05 ml) that had been given to all patients of both groups to help improve outcomes after glaucoma surgery. Liu et al.[10] in a study of comparison between combined anti-VEGF with trabeculectomy and AGV also had similar findings in NVG eyes.
It is important to note that, unlike previous studies on GDDs where scleral patch graft or pericardial graft was used, here AM-UC graft taken from the junction of the umbilical cord and the placenta was used for the tube shunt coverage for the AGV group. AM-UC has antifibrotic, anti-immunogenic, and antiangiogenic properties and provides good tectonic support of the tube shunt allowing direct visualization of the tube.[11] Tube exposure was not seen in any patients of the AGV group.
The expenses of the modified trabeculectomy surgery are lower than that of AGV implantation which is statistically significant as it is very similar to the conventional trabeculectomy, only having an extra step that requires an 8-0 polypropylene suture [Fig. 3]. The AGV device, on the other hand, is an expensive GDD that is out of reach for most patients. Thus, the newly developed polypropylene-based modified trabeculectomy may be recommended for patients from moderate to low socio-economic groups in developing countries.
Figure 3.
Surgical step showing the preparation of polypropylene bed in trabeculectomy (using polypropylene)
A major limitation of this study is its short follow-up period and small sample size. The small sample size increases the possibility of a type II (false negative) statistical error. Since all patients included in the study were male there is a possibility of gender bias in the present study.
Conclusion
Both AGV implantation and modified trabeculectomy had similar IOP reduction and short-intermediate term surgical success rates in the treatment of NVG. However, the cost of surgery incurred by the patient was lower for the modified trabeculectomy group as compared to AGV. Thus, modified trabeculectomy with polypropylene suture may be a better alternative to AGV implantation in eyes with NVG.
Financial support and sponsorship:
Nil.
Conflicts of interest:
There are no conflicts of interest.
References
- 1.Dumbrăveanu L, Cușnir V, Bobescu D. A review of neovascular glaucoma. Etiopathogenesis and treatment. Rom J Ophthalmol. 2021;65:315–29. doi: 10.22336/rjo.2021.66. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Mo B, Li SF. Novel use of an adjustable single 8-0 polypropylene suture of scleral fixation without conjunctival dissection. BMC Ophthalmol. 2020;20:304.. doi: 10.1186/s12886-020-01558-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.John T, Tighe S, Hashem O, Sheha H. New use of 8-0 polypropylene suture for four-point scleral fixation of secondary intraocular lenses. J Cataract Refract Surg. 2018;44:1421–5. doi: 10.1016/j.jcrs.2018.08.008. [DOI] [PubMed] [Google Scholar]
- 4.Abdelrahman AM, El-Sayed YM. Prolene canalostenting in deep sclerectomy: A pilot study. Middle East Afr J Ophthalmol. 2015;22:514516.. doi: 10.4103/0974-9233.167810. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Hyung SM, Kim SK. Mid-term effects of trabeculectomy with mitomycin C in neovascular glaucoma patients. Korean J Ophthalmol. 2001;15:98–106. doi: 10.3341/kjo.2001.15.2.98. [DOI] [PubMed] [Google Scholar]
- 6.Mandal AK, Majji AB, Mandal SP, Das T, Jalali S, Gothwal VK, et al. Mitomycin-C-augmented trabeculectomy for neovascular glaucoma. A preliminary report. Indian J Ophthalmol. 2002;50:287–93. [PubMed] [Google Scholar]
- 7.Yalvac IS, Eksioglu U, Satana B, Duman S. Long-term results of Ahmed Glaucoma Valve and Molteno implant in neovascular glaucoma. Eye. 2007;21:65–70. doi: 10.1038/sj.eye.6702125. [DOI] [PubMed] [Google Scholar]
- 8.Im YW, Lym HS, Park CK, Moon JI. Comparison of mitomycin C trabeculectomy and Ahmed Valve Implant surgery for neovascular glaucoma. J Korean Ophthalmol Soc. 2004;45:1515–21. [Google Scholar]
- 9.Shen CC, Salim S, Du H, Netland PA. Trabeculectomy versus Ahmed Glaucom Valve implantation in neovascular glaucoma. Clin Ophthalmol. 2011;5:281–6. doi: 10.2147/OPTH.S16976. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Liu L, Xu Y, Huang Z, Wang X. Intravitreal ranibizumab injection combined trabeculectomy versus Ahmed valve surgery in the treatment of neovascular glaucoma: Assessment of efficacy and complications. BMC Ophthalmol. 2016;16:65.. doi: 10.1186/s12886-016-0248-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Sheha H, Tello C, Al-Aswad LA, Sayed MS, Lee RK. Outcomes of the shunt tube exposure prevention study: A randomized clinical trial. Ophthalmol Glaucoma. 2019;2:392–401. doi: 10.1016/j.ogla.2019.08.003. [DOI] [PMC free article] [PubMed] [Google Scholar]