One-Year Results of Stab Incision Glaucoma Surgery and Radiofrequency-Assisted Stab Incision in Management of Open-Angle Glaucoma.

PURPOSE: The aim of the study is to evaluate the surgical outcome of stab incision glaucoma surgery (SIGS) and compare it with radiofrequency-assisted stab incision in the treatment of uncontrolled open-angle glaucoma. PATIENTS AND METHODS: A prospective, interventional study included 50 eyes who were assigned into two equal groups: Group A underwent stab incision procedure with preoperative subconjunctival (SC) mitomycin-C (MMC) and Group B underwent radiofrequency-assisted technique without MMC. Intraoperative and postoperative complications, visual acuity, intraocular pressure (IOP), and bleb status were evaluated up to 12 months.
RESULTS: Mean preoperative IOP in Group A was 26.96 ± 2.42 reduced to 13.43 ± 2.31 while in Group B was 27.20 ± 3.57 reduced to 15.48 ± 3.68 mmHg (P < 0.001) with a mean reduction of 50.61% ± 8.42% and 43.56% ± 12.83%, 12 months postoperatively in Groups A and B, respectively. Non-basal peripheral iridectomy was the most encountered intraoperative complication in 8 eyes (32%) and 9 eyes (36%) and hypotony was the most reported postoperative complication in 5 eyes (20%) and 9 eyes (36%) in Groups A and B, respectively. Flat bleb area had been reported at the end of follow-up time in 3 eyes (13%) and 7 eyes (30%) in Groups A and B, respectively. Complete success rate was 52.2% and 28.6% while qualified success rate was 28.8% and 42.9% in Groups A and B, respectively.
CONCLUSION: SIGS with SC MMC is an effective and safe procedure in IOP lowering, while radiofrequency-assisted stab incision had high incidence of subconjunctival scarring and ostium closure. Copyright:

RCT Entities:   Population Interventions Outcomes

Introduction

Subscleral trabeculectomy was innovated in 1968, and since then, it has been considered the surgical tool of choice in glaucoma management.[123] In spite of its efficacy in controlling intraocular pressure (IOP), the complications related to conjunctival dissection, preparation of scleral flap, and suturing were found to be responsible for enhancing scarring and fibrosis at the surgical site.[4] Stab incision glaucoma surgery (SIGS) is a new guarded filtration procedure that was firstly described by Jacob and Agarwal in 2014 based on decreasing the conjunctival manipulation, expecting to reduce subconjunctival (SC) fibrosis with better aqueous drainage.[56]

The principle of radiofrequency surgery is to use high-frequency radio waves to deliver low temperatures so that its cutting effect is performed without manual pressure or crushing tissue cells, thus resulting in tissue healing without fibrous contractile scar tissue.[7] In ophthalmology, radiofrequency was initially used for refractive surgery in 1981 to treat keratoconus, and later, it was used for oculoplastic, conjunctival, and glaucoma surgeries.[8]

In this study, we evaluated the surgical outcome regarding IOP, advantages, disadvantages, and surgical challenges of SIGS as a substitute for conventional subscleral trabeculectomy in the management of uncontrolled open-angle glaucoma (OAG) and comparing its results with radiofrequency-assisted stab incision technique throughout 1-year follow-up.

Patients and Methods

A prospective, comparative interventional randomized study was carried out at Cairo University Hospitals, Cairo University, from March 2015 to March 2018. The study was approved by the Cairo University Research Ethics Committee and followed the tenets of the Declaration of Helsinki. Informed consent for the surgery and for the study was obtained from all patients.

Patients with uncontrolled OAG aged from 40 - 70 years old, with IOPs not reaching the target pressure despite the administration of maximally tolerated medications or had poor compliance to treatment, were included in this study. Exclusion criteria were any previous conjunctival or intraocular surgery, presence of significant cataract, and cases of congenital, traumatic, neovascular, uveitic, narrow, or angle-closure glaucomas. Fifty eyes of 50 patients were randomly recruited into two comparative groups: Group A – 25 eyes who underwent SIGS with preoperative SC mitomycin-C (MMC) 0.02% and Group B – 25 eyes who underwent radiofrequency-assisted SIGS using Ellman Surgitron FFPF EMC device (USA) without MMC application.

Preoperative thorough ophthalmological examination was performed. All included patients had corrected visual acuity (CDVA) assessment using Snellen charts. Anterior segment examination was done using a slit lamp; IOP was measured using Goldmann applanation tonometry, detailed fundus examination including cup/disc (C/D) ratio was done, and gonioscopy for anterior chamber (AC) angle evaluation was performed.

Surgery was done under retrobulbar anesthesia. In Group A, 0.2 ml of 0.02% MMC was injected subconjunctivally 6 mm above the limbus at the intended site of bleb filtering area and was left for 20 min before starting the surgery. Paracentesis was done at 9 o'clock. Superior conjunctiva was slid downward over the cornea, and a 2.8 mm bevel-up metal keratome was introduced 1.5 mm behind the limbus; then, the tip of the keratome was passed through the conjunctiva into superficial lamellar sclera. A superficial lamellar scleral tunnel was then dissected with the passage of the keratome till the limbus. The blade was then introduced 0.5 to 1 mm into clear cornea before entering the AC. Reformation of the AC was done by viscoelastic material injected through the paracentesis. The internal lip of the corneal was punched by 1 mm Kelly Descemet's punch (G-13238, Kelly Glaucoma Punch, GEUDER AG, 19 gauge/1.0 mm), the basal part of the iris was grasped through the tunnel with nontoothed forceps, and peripheral iridectomy (PI) was done with curved Vannas scissors; then, the balanced salt solution (BSS) was irrigated through the paracentesis, and filtration through the SIGS tunnel was assessed. Free flow of fluid through the ostium on irrigation was considered to be the end point for optimum filtration. In case of inadequate filtration, additional punches were taken. The conjunctival cut was sutured with interrupted 10-0 nylon suture. Gentamicin 80 mg/2 ml and dexamethasone 4 mg/ml were subconjunctivally injected, and the eye was patched.

In Group B, the radiofrequency waves emitted from Ellman Surgitron radiofrequency device were delivered to the sclera using a customized radiofrequency keratome 2.8 mm. Antenna plate was placed under the patient's left shoulder to direct the wave then a fully filtered (cut) waves, 90% cutting and 10% coagulating mode was used to dissect the scleral tunnel. The first stab entry was done without activation of the radio wave, and then, viscoelastic cohesive substance (sodium hyaluronate 1%, Healon) was injected in SC space at the site of keratome entry acting as a heat insulator to protect the conjunctiva from thermal effect of radio wave in order to avoid tissue shrinkage and buttonhole occurrence. After entering the AC, all surgical steps were completed as SIGS surgery described in Group A.

Postoperatively, topical moxifloxacin 0.5% eye drops were routinely used for the 1st2 weeks, and topical prednisolone acetate 1% eye drops were prescribed for 2 months with gradual tapering. At days 1 and 7 and at 1, 3, 6, 9, and 12 months postoperatively, the patients were thoroughly examined by slit lamp for the IOP measurements, which was the main outcome using Goldmann applanation tonometry. The secondary outcomes were CDVA, number of glaucoma medications, PI patency, wound integrity, and reported complication with special attention to the bleb grading using the Indiana Bleb Appearance Grading Scale (IBAGS).[9] Anterior segment optical coherence tomography (AS-OCT) was done when needed postoperatively to confirm ostium patency and bleb filtration.

Complete success was defined as IOP ≤21 mmHg without any antiglaucoma medication; qualified success was defined as IOP ≤21 mmHg with using ≤2 antiglaucoma medications at the end of follow-up period,[1011] and failure was considered when ≥2 antiglaucoma medications or resurgery was required to control IOP.

For statistical analysis, Snellen visual acuities were converted to logMAR values. Comparisons between quantitative variables in the two groups were done using unpaired t-test or the nonparametric Mann–Whitney test. Repeated measures analysis of variance (ANOVA) was used to compare data for continuous variables. Wilcoxon signed-rank test was used for nonnormally distributed quantitative variables. For comparing categorical data, Chi-square test was performed. Fisher's exact test was used instead when the expected frequency is <5. P < 0.05 was considered statistically significant. Statistical analysis was performed using SPSS for Windows (SPSS Inc., Chicago, IL, USA).

Results

Two patients in Group A had lost their follow-up since the 2nd month postoperatively. In Group B, 3 patients did not complete the follow-up visits after the 3rd month and another patient developed sight-threatening complication after the 3rd month that necessitated further surgical intervention (he was included in complications but not in the statistical analysis of IOP).

A total of 50 eyes from 50 patients (28 males and 22 females) were included in this study. The patients were randomly assigned into two groups. The mean age was 57.40 ± 7.38 years and 54.76 ± 8.31 years in Groups A and B, respectively. In Group A, 19 eyes had primary OAG (76%), 6 eyes had secondary OAG (24%), 4 were pseudoexfoliation glaucoma (PEG), and 2 were pigmentary glaucoma (PG). However, in Group B, 20 eyes had primary OAG (80%) and 5 eyes had secondary OAG (20%) (3 were PEG and 2 were PG).

As shown in Table 1, the mean reduction of IOP in Group A was 50.61% ± 8.42% at the end of the 12th month postoperatively (P < 0.001), which was most significant 1 month postoperatively (P < 0.001). However, there was a significant increase in IOP values at the 3rd month (P = 0.039) compared to the 1st month (ANOVA test), while in Group B, the mean reduction of IOP was 43.56% ± 12.83% at the end of the 12th month postoperatively (P = 0.001), which was most significant 1 month postoperatively (P < 0.001). Meanwhile, a significant increase in IOP readings was reported by the end of the 3rd month (P = 0.001) compared to the 1st month (ANOVA test).

Table 1

Pre- and postoperative data of (mean logarithm of the minimum angle of resolution best-corrected visual acuity, intraocular pressure, and number of medication) throughout 12 months’ follow-up in each Groups A and B

	Group A, mean±SD	P	Group B, mean±SD	P
Pre-BCVA	0.86±0.34	0.104	0.89±0.27	0.004
Post-BCVA	0.93±0.36		0.98±0.34
Pre-IOP mmHg	26.96±2.42	<0.001	27.20±3.75	<0.001
†IOP 1st week	8.20±4.30		10.48±4.94
†IOP 1st month	13.76±4.96		16.12±4.82
†IOP 3rd month	15.70±5.00		20.04±5.63
†IOP 6th month	13.83±3.92		16.00±4.42
†IOP 9th month	13.74±2.70		15.75±3.12
†IOP 12th months	13.43±2.31		15.48±3.68
‡No medication preoperatively	2.64±0.57	<0.001	2.64±0.75	<0.001
‡No medication postoperatively	0.74±1.01		1.43±1.21

BCVA: Best-corrected visual acuity, †IOP: Intraocular pressure, ‡No: Number, SD: Standard deviation

Complete success rate was 52.2% in Group A and 28.6% in Group B, and qualified success rate was 28.8% and 42.9% in Groups A and B, respectively. Three eyes (13%) and six eyes (28.6%) were considered as failed cases in Groups A and B, respectively, as they required ≥2 antiglaucoma eye drops to control IOP.

In Group A, preoperative logMAR CDVA was 0.86 ± 0.34 insignificantly reduced to 0.93 ± 0.36 at the end of the follow-up period (P = 0.104). However, in Group B, the preoperative logMAR CDVA was 0.89 ± 0.27 and 0.98 ± 0.34 postoperatively with a significant reduction (P = 0.004).

Comparing the preoperative data of Groups A and B regarding (age, logMAR CDVA, IOP, type of glaucoma, C/D ratio, and number of medications), there was no statistical difference. However, postoperative IOP was significantly lower in Group A than in Group B from the 2nd month all through the follow-up period, as shown in Table 2 and Figure 1.

Table 2

Statistical difference of both groups regarding preoperative data and along the follow-up postoperative data

	Mean±SD		P
	Group A	Group B
Age (years)	57.40±7.38	54.76±8.31	0.241
Pre-BCVA	0.86±0.34	0.89±0.27	0.746
Post-BCVA	0.93±0.36	0.98±0.34	0.730
Pre-IOP mmHg	26.96±2.42	27.20±3.57	0.782
†IOP 1st week	8.20±4.30	10.48±4.94	0.088
†IOP 1st month	13.76±4.96	16.12±4.82	0.094
†IOP 3rd month	15.70±5.00	20.04±5.63	0.008
†IOP 6th month	13.83±3.92	16.00±4.42	0.091
†IOP 9th month	13.74±2.70	15.57±3.12	0.043
†IOP 12th month	13.43±2.31	15.48±3.68	0.037
‡No medication preoperatively	2.64±0.57	2.64±0.57	1
‡No medication postoperatively	0.74±1.01	1.43±1.21	0.048
C-D ratio	0.76±0.11	0.74±0.11	0.603

BCVA: Best-corrected visual acuity, †IOP: Intraocular pressure, ‡No: Number, SD: Standard deviation

Figure 1

Intraocular pressure in Groups A and B during the follow-up time

Intraoperative complications of both Groups A and B were encountered and illustrated with their incidence in Figure 2 with no significant difference between both groups.

Figure 2

Intraoperative complications in Groups A and B

Early (first 3 months) and late postoperative complications (from the 3rd month till the end of follow-up time) with their indices were reported in both the groups [Table 3] with no significant difference except in mild iritis (Grade II) which was detected within 48 h postoperatively and managed medically with topical prednisolone acetate every 2 h and atropine sulfate every 8 h for 5 days.

Table 3

Early and late postoperative complications in both groups

	Group A (%)	Group B (%)	P
Early postoperative complications	25 eyes	25 eyes
Grade II iritis	3 (12)	9 (36)	0.047
Hypotony	5 (20)	9 (36)	0.208
Hypotony with shallow or flat †AC	2 (8)	4 (16)	0.667
Conjunctival leakage	1 (4)	1 (4)	1
Microhyphema	2 (8)	3 (12)	1
Serous choroidal detachment	3 (12)	4 (16)	1
Suprachoroidal hematoma	0 (0.00)	1 (4)	1
Elevated ‡IOP with deep †AC	4 (16)	2 (8)	0.667
Elevated ‡IOP with lost †AC (aqueous misdirection)	0 (0.00)	0 (0.00)	-
Late postoperative complications	23 eyes	22 eyes
Complicated cataract to surgical manipulation	2 (8.6)	2 (9)	1
Endophthalmitis	0 (0.00)	1 (4.5)	0.489
Chronic hypotony	1 (4)	0 (0.00)	1
Ptosis	0 (0.00)	3 (13.6)	0.109

†AC: Anterior chamber, ‡IOP: Intraocular pressure

Six eyes in both the groups were found to have high IOP 2nd day postoperatively with formed AC and no obvious bleb, and ocular massage with frequent steroids (every 2 h) was given to prevent subsequent scarring and premature failure. AS-OCT done for two cases (one in each group) revealed that the ostium was occluded by the iris [Figure 3], and synechiolysis was done with a marked reduction in IOP. Two eyes in Group A had encysted bleb on the 2nd month of follow-up and were managed by bleb needling and SC injection of MMC. Flat bleb area had been reported at the end of follow-up time (12 months) in 3 eyes (13%) and 7 eyes (30%) in Groups A and B, respectively, and noticed that it was much lower in Group A where MMC had been used.

Figure 3

(a) Slit-lamp photograph of flat fibrosed bleb area and site of taken punch could be noticed (blue arrow) in Group A. (b) Gonioscopic photograph showing occluded ostium. (c) Anterior segment optical coherence tomography showing site of taken punch (blue arrow) with hyperreflective scarred subconjunctival area

Hypotony (IOP ≤ 5 mmHg) due to overfiltration was reported 1st day postoperatively, and they were managed by topical atropine sulfate three times/day and reduced frequency of topical steroids (three times/day). However, in eyes where hypotony was associated with flat or shallow AC with formed bleb area [Figure 4], in addition to the above measures, pressure bandage was done and oral carbonic anhydrase inhibitor 250 mg ½ tablet/8 h was given. In nonresponding eyes (one eye in each group), AC reformation with viscocohesive (sodium hyaluronate) was done. In Group A, one eye (4%) developed chronic hypotony, maculopathy, and choroidal folds for >3 months and the patient refused any further intervention.

Figure 4

Slit-lamp photograph shows diffuse filtering bleb area in a patient in Group A (blue arrow); site of keratome entry could be noticed (red arrow)

Serous choroidal effusion with localized annular detachment was reported during the 1st week postoperatively and was resolved on frequent topical steroids, atropine sulfate 1% three times, and systemic oral prednisolone 1 mg/kg/day until the IOP built up. Hypotony due to conjunctival wound leakage in one eye (4%) in each group was reported and managed conservatively.

Microhyphema was noticed 1st day postoperatively and was resolved within 3 days. One eye (4%) in Group B developed localized suprachoroidal hematoma confirmed by Ocular Ultrasound and resolved spontaneously with topical and systemic steroids within 1 week.

Late blebitis with endophthalmitis was encountered in one eye (4.5%) in Group B in poorly controlled diabetic patient 4 months postoperatively and required core vitrectomy.

At the end of follow-up period, the bleb appearance was assessed and classified according to the IBAGS, and there was no statistical difference between both the groups in bleb-related complications.

Discussion

Subscleral trabeculectomy is the most common glaucoma-filtering surgery. However, it is usually described with significant complications that are related to scleral flap preparation and suture-related problems.[12] Wound healing process is still the major limiting factor of filtering surgery success because of scarring at the level of the conjunctiva, Tenon's capsule, and episcleral interface.[13] SIGS is a guarded filtration procedure that was firstly described by Jacob and Agarwal[56] to simplify and avoid some of the conventional trabeculectomy complications. Wound healing in response to conjunctival dissection can compromise surgery success due to obstruction of aqueous outflow and lack of filtration,[4] and thus, decreasing the intraoperative conjunctival manipulation may reduce SC fibrosis and enhance aqueous drainage in the long term.[14] In the present study, conjunctival dissection was markedly minimized, and this was thought to minimize the risk of scarring and increase the preservation of virgin conjunctiva for other possible future surgeries. However, the end results of this study did not meet our expectations, and cases with failure were reported due to fibrosis at the bleb area and their incidence was not so far from those reported in conventional trabeculectomy.

SIGS follows the same principle of sutureless tunnel trabeculectomy which was first described in 1999 as a successful mode of filtration surgery.[15] Formation of scleral tunnel instead of a flap was found to reduce the lateral and forward outflow of aqueous which in turn can reduce postoperative leakage. Aqueous outflow was also directed through a single outflow channel instead of two- or three-sided flap as in conventional trabeculectomy, thus maintaining the patency of created fistula.[16] The simplicity in scleral tunnel creation reduced the operation time and flap-related complications, which was an important advantage of SIGS over conventional trabeculectomy that was also reported by Jacob et al.[6] In the present study, scleral tunnel was left sutureless and the small conjunctival incision was closed by maximum two interrupted 10-0 nylon sutures, so that the perioperative problems involving the conjunctival and scleral flap that had been thought to be responsible for the postoperative complications of trabeculectomy were nearly eliminated.[17] The risk of suture-associated complications such as buttonholing and suture abscess was minimized. Postoperative manipulations of sutures such as suture release or laser suture lysis which carry an additional risk of complications were also eliminated. All these reported advantages coincided with those described by Jacob et al. in 2016.[6]

Preoperative SC MMC used in Group A in order to minimize conjunctival scarring was found to be easy and safe. This method is widely known and accepted by glaucoma surgeons as the dose is more titratably delivered compared to the variability with sponge delivery, and the application area is more diffuse, which promotes a more diffuse posterior bleb with more time-saving.[181920]

Some intraoperative challenges such as SC hemorrhage during keratome entry were reported mainly in early cases and were overcome later by avoiding major blood vessels during the tunnel dissection. This was also reported as potential disadvantage by Jacob et al.[6] and also in conventional trabeculectomy during conjunctival dissection despite using diathermy.[21] The incidence was less in Group B due to the ability of radiofrequency waves to control bleeding by its coagulating effect as reported in the literature.[22] Scleral tunnel dissection in proper plane was one of the difficulties, as premature entry in early cases was encountered and managed by a small taken punch with no reported impact on IOP. Its higher incidence compared to Jacob et al.'s study[6] could be explained by learning curve as the partially blind dissection of the scleral tunnel was done under almost intact conjunctiva.

PI was the most important intraoperative challenge as grasping the basal part of the iris through a narrow tunnel was completely blind and not a few cases of non-basal PI were encountered during the study. This reported difficulty coincided with Eslami et al. in 2012, who found that sutureless tunnel trabeculectomy without PI was effective in reducing IOP.[23]

In the present study, conjunctival buttonhole was small and required no intervention due to the extremely minimized conjunctival manipulation, which was not far from Jacob et al.'s results as they reported one case of buttonhole (5.9%).[6]

Hypotony due to overfiltration was the most reported early postoperative complication during the study, and this was different from Jacob et al.'s results as only one eye (5.9%) with hypotony was reported.[6] This could be explained by large ostium created in some cases by taking multiple punches and the sutureless scleral tunnel. However, the higher incidence in Group B could be explained by tissue shrinkage during scleral tunnel dissection using radiofrequency waves resulting in poor apposition and loss of its valvular effect. Hypotony due to conjunctival wound leakage was encountered in only one eye in each group due to minimal conjunctival manipulation which was markedly reduced compared to conventional trabeculectomy as national survey reported 216 eyes (17.8%)[17] and Leeungurasatien et al. reported 8 eyes (8.8%).[24]

In Group B, IOP was found to increase at the 3rd month that necessitated the usage of antiglaucoma drops resulting in high percentage of qualified success eyes which might be explained by lacking of MMC use and inefficacy of radiofrequency waves to be an alternative to the use of antifibrotic modulators. Which was different from reported results in literature about its efficacy as an alternative to MMC.[25] The increased production of lateral heat due to the large-sized electrode (2.8 mm keratome) used in the scleral tunnel dissection in our study was thought to be responsible for enhanced scarring and fibrosis.

In Group B, there was a significant reduction in BCVA postoperatively that could be explained by the higher incidence of hypotony and shallow AC recorded that had a negative impact on corneal clarity and aggravated lens opacification.

The results of Groups A and B as regards IOP were comparable to those reported by Jacob et al. regarding the mean postoperative IOP (16.47 ± 4.81 mmHg) and the mean reduction in IOP (38.81% ±16.55%).[6] Complete success was reported in 64.7% and qualified success in 17.65% that was different from ours (52% and 35% in Group A and 28.6% and 43% in Group B, respectively). The end results of Group A were comparable to those reported after conventional trabeculectomy, as target pressure between 18 and 22 mmHg has been variously reported to range from 43% to 86% without medications and from 59% to 98% with medications,[262728] which was not the case in Group B.

Although SIGS appeared to have comparable results to conventional trabeculectomy in IOP reduction and in decreasing the number of antiglaucoma medications in patients with OAG, the small sample size and the limited follow-up make it difficult to draw a strong conclusion. No doubts that the elimination of conjunctival dissection and the fashioning of scleral tunnel were beneficial in reducing the operation time and complications related to scleral flap creation and suturing but also appeared to have no role in controlling the filtration or minimizing postoperative scarring and fibrosis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.