Intraoperative optical coherence tomography–guided transconjunctival bleb suturing – A minimally invasive technique for managing overfiltering bleb

Abstract

With the recent advancement in technologies, real-time integrated intraoperative optical coherence tomography (iOCT) microscopes are available, which facilitates surgical precision and also reduces the risk of complications. Two glaucoma patients with advanced glaucomatous optic neuropathy, who underwent uneventful trabeculectomy with 0.02% mitomycin C, developed persistent hypotony postoperatively till 4–6 weeks. On clinical examination, visual acuity was 1/60 with low intraocular pressure (IOP) of 4 mmHg. Elevated, overfiltering bleb was seen on slit-lamp examination, along with hypotonous maculopathy. Anterior segment optical coherence tomography (AS-OCT) showed multiple large hyporeflective fluid spaces suggestive of overfiltering bleb. Considering the risk of choroidal detachment and further deterioration of vision, iOCT-guided transconjunctival bleb suturing was planned. iOCT helped to identify the exact location of scleral flap, and transconjunctival suturing was done with successful outcomes in terms of improved IOP and visual acuity.

After trabeculectomy, aqueous humor flows into the surgically created filtering bleb.[1] It is a challenge faced by both surgical technique and postoperative care to maintain the balance in intraocular pressure (IOP) low enough not only to obtain the target pressure, but also to avoid complications like hypotonic maculopathy. Clinically significant hypotony is defined as the condition where IOP is low enough to result in visual loss.[2] Hypotonic maculopathy is one of the significant causes of delayed recovery following trabeculectomy. There are various treatments available for the management of overfiltering blebs. Conservative treatment includes topical autologous serum,[3] bleb injection of autologous blood or viscolelastic material,[4] and anterior chamber injection of gas[5] or viscoelastic material.[6] Whereas surgical management includes transconjunctival flap suturing,[7,8] excision of thin blebs and conjunctival advancement,[9] and patch grafting by autologous conjunctiva.[10] Transconjunctival suturing of the scleral flap was described as a safe and effective treatment for excess filtration.[11]

Anterior segment optical coherence tomography (AS-OCT) allows a detailed assessment of bleb, its internal anatomy, and underlying scleral flap, thereby providing an in vivo imaging similar to the histological sections, which is very useful for determining the exact surgical site for intervention.

The use of intraoperative optical coherence tomography (iOCT) is one of the recent advances described in the field of glaucoma surgeries. It has been used for trabeculectomy, Ahmed glaucoma valve (AGV), bleb-sparing epithelial exchange,[12] bleb needling,[13] goniosynechialysis, etc., We report the use of iOCT as an adjunct in transconjunctival bleb suturing for the management of overfiltering bleb with hypotonic maculopathy, which provides the exact location of the scleral flap in vivo.

Case 1

A 29-year-old male with a history of juvenile open-angle glaucoma with advanced glaucomatous optic neuropathy underwent left eye trabeculectomy with mitomycin-C 0.02%. The patient had an IOP of 4–6 mmHg on postoperative day 1 and day 7. Conservative management by lowering topical steroids and oral steroids was started. However, at 4 weeks of follow-up, he had persistent low IOP of 3–4 mmHg in the left eye and the vision was 1/60. Slit-lamp examination showed a superior elevated bleb extending for three clock hours with no leak on Seidel’s test (H3V2E3S0), and the anterior chamber depth was moderate to deep. Bleb AS-OCT showed an elevated bleb with large subscleral lake of fluid suggestive of an overfiltering bleb [Fig. 1a]. Fundus showed features of hypotonic maculopathy, which were confirmed on macular optical coherence tomography (OCT) [Fig. 1c].

Figure 1.

(a) Preoperative bleb AS-OCT showing an elevated bleb with large subscleral lake of fluid suggestive of an overfiltering bleb. (b) Postoperative AS-OCT showing decrease in bleb height and subscleral fluid. (c) Preoperative macular OCT showing features of hypotonic maculopathy. (d) Postoperative macular OCT showing resolution of macular folds. AS-OCT = anterior segment optical coherence tomography

Case 2

A 41 year old male diagnosed as Myopia with left eye healed anterior uveitis with secondary glaucoma with advanced Glaucomatous Optic Neuropathy underwent left eye trabeculectomy with mitomycin-C 0.02%. He had persistent low IOP of 3–4 mmHg in the left eye and the vision was 1/60. Slit-lamp examination showed a superior elevated bleb extending for three clock hours with no leak on Seidel’s test (H3V2E3S0), and the anterior chamber depth was moderate to deep. Bleb AS-OCT showed an elevated bleb with multiple large fluid spaces underneath, suggestive of an overfiltering bleb [Fig. 2a]. Fundus showed features of hypotonic maculopathy (pseudopapilledema, tortuous vessels, and macular folds) [Fig. 2c].

Figure 2.

(a) Preoperative bleb AS-OCT showing an elevated bleb with multiple large fluid spaces underneath, suggestive of an overfiltering bleb. (b) Postoperative AS-OCT showing decrease in bleb height and resolution of multiple cystic spaces. (c) Preoperative fundus photo showing features of hypotonic maculopathy (pseudo papilledema, tortuous vessels, and macular folds). (d) Postoperative fundus photo of macular OCT showing resolution of macular folds. AS-OCT = anterior segment optical coherence tomography

Surgical Technique

Transconjunctival bleb suturing was done after taking a written informed consent, using an iOCT RESCAN 700 (Carl Zeiss Meditec, Jena, Germany) fused with OPMI LUMERA 700 microscope (Carl Zeiss Meditec, Germany). The Calisto eye displays the live surgical and OCT view on the common screen together.

The eye was anaesthetized with peribulbar block (0.5% bupivacaine + 2% lignocaine), and then a wire speculum was inserted. After direct visualization of bleb depth on iOCT, 10-0 monofilament nylon sutures were placed transconjunctivally in the area of the bleb.[11] Radial 10-0 nylon sutures were placed starting near the limbus and extending posteriorly toward the posterior fornix. After placing five sutures, paracentesis was done and balanced salt solution (BSS) was injected into the anterior chamber to assess the increase in IOP and reduction of the outflow under iOCT guidance. In vivo, preoperative and postoperative assessment of the bleb was done on iOCT [Fig. 3a and b]. Postoperatively, topical antibiotic–steroid combination eyedrops and ointment were prescribed in tapering doses for 4 weeks. The patient was followed up at day 1, week 1, and 1, 3, and 6 months after the surgery.

Figure 3.

(a) Intra-operative clinical photograph showing a hyperfiltering bleb. The corresponding live iOCT imaging- horizontal scan (blue horizontal line) and vertical scan (red vertical line) of the bleb area shows an elevated bleb with multiple cystic spaces. (b) iOCT imaging after placing the transconjunctival sutures shows reduction in bleb height with cystic spaces. iOCT = intraoperative optical coherence tomography

Results

After transconjunctival bleb suturing, in the first patient, IOP improved to 12 mmHg during the first postoperative week follow-up and was maintained till 6 months of follow-up. Visual acuity improved to preoperative levels at 1-month follow-up and there was complete resolution of hypotonic maculopathy [Fig. 1d]. The bleb was present over the superior limbus extending for two consecutive clock hours. AS-OCT of the bleb postoperatively showed a decrease in the bleb height and smaller hyporeflective spaces within the bleb tissue [Fig. 1b].

In the second patient, IOP improved to 10 mmHg during the first postoperative week follow-up. IOP at 4 months of follow-up was 12 mmHg. Visual acuity improved to preoperative levels at 1-month follow-up, and there was complete resolution of hypotonic maculopathy [Fig. 2d]. AS-OCT of the bleb postoperatively showed a decrease in the bleb height and smaller hyporeflective spaces within the bleb tissue [Fig. 2b].

Discussion

OCT plays a significant role in the diagnosis, management, and monitoring of many ocular pathologies. Microscope-integrated OCT further increases surgical precision in corneal and glaucoma surgeries. The role of iOCT has been described in bleb needling[13] and bleb-sparing epithelial exchange.[12] In cases of overfiltering bleb, transconjunctival suturing helps to tackle the overfiltering bleb and thereby increase IOP. But the dilemma lies in where to place the suture, as it is not always apparent, especially in cases of overfiltering blebs where the conjunctiva is elevated and there is difficulty in visualizing the underlying scleral flap.

The introduction of iOCT gives real-time cross-sectional image of the bleb during surgery. The areas of excessive filtration were identified by the presence of hyporeflective fluid pockets. The sutures were targeted toward these areas. The number of suture application was titrated according to the reduction in the intraoperative OCT bleb height, seen under direct visualization. It prevents inadvertent damage to the underlying bleb structures/sclera. The heads-up 3D display provides the surgeon with rapid visualization of the area of interest and the instrument– tissue interaction. It proves to be an excellent teaching tool for trainees as well. Limitations are the higher cost and rare availability of the microscope.

Conclusion

Our technique of iOCT-guided transconjunctival bleb suturing increases the surgical precision and outcome, as well as decreases the surgical time and complications.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.