Blebophthalmos: proptosis due to a massive bleb following implant surgery in refractory paediatric glaucoma

Abstract

A 5-year-old boy with failed combined trabeculotomy and trabeculectomy underwent Ahmed glaucoma valve (AGV) implantation and presented 5 weeks postoperatively, with sudden onset proptosis downward displacement of the globe, limited extraocular movements and displacement of tube from anterior chamber. CT scan of the orbits showed a large cystic bleb with posterior dislocation of the implant and was explanted. In vitro testing of implant for fluid flow characteristics revealed a dysfunctional valve with anterior leak, which could have possibly lead to anterior and inferior fluid accumulation resulting in displacement of implant, a probable cause for this rare complication. The case was successfully managed later with the Aurolab aqueous drainage device implantation. This case report cautions the surgeon for the possibility of a large cystic bleb following abnormal leak in AGV resulting in orbital complications like proptosis, motility limitation and impending optic nerve compression.

Background

Ahmed glaucoma valve (AGV) is a unidirectional flow restrictive aqueous drainage device indicated in refractory glaucoma.¹

Complications associated with implant surgery are conjunctival dehiscence or retraction, tube erosion, tube migration and implant exposure and rarely, orbital complications.^{2 3}

We report a rare orbital complication after AGV implantation in a child with congenital hereditary endothelial dystrophy (CHED) and congenital glaucoma.

Case presentation

A 5-year-old boy with failed trabeculotomy and trabeculectomy for bilateral congenital glaucoma along with CHED presented to us with raised intraocular pressure (IOP) (right eye (RE): 42 mm Hg, left eye (LE): 24 mm Hg) and corneal oedema resulting in poor fundus visibility. Horizontal corneal diameter was 12.5 mm with central corneal thickness greater than 1000 µm in both eyes and axial length was 24 mm in RE and 21 mm in LE.

Due to medically uncontrolled IOP in the RE, FP7 AGV was implanted in the superotemporal quadrant, implant was fixed with two 10–0 Prolene anchoring sutures 8 mm from the limbus, tube was inserted into the anterior chamber through a 3 mm scleral tunnel, secured with 10’0 nylon sutures and covered with a scleral patch graft, which was anchored with fibrin glue and additional two anterior anchoring 10’0 nylon sutures. Postoperatively, topical steroids in tapering doses, antibiotics and cycloplegics were prescribed and by third week aqueous suppressants were initiated when hypertensive phase was detected. Corneal clarity improved and lamellar cataract was visible in both the eyes.

Five weeks postoperatively, child presented with RE sudden onset proptosis with resistance to retropulsion, hypotropia (figure 1A) and severe limitation of extraocular movements in all gazes of 2 days duration. On slit lamp examination, a large diffuse thick-walled bleb in the superotemporal location was noted but the tube was not visible in the anterior chamber (figure 1B), and the IOP was 34 mm Hg in the RE. On fundus examination, large cup with 0.7 cup-to-disc ratio was noticed but other details were not clear.

Figure 1.

(A) Right eye (RE) proptosis with inferior displacement of the globe. (B) Superotemporal cystic bleb with an intact scleral patch graft, tube not visualised in the anterior chamber.

Investigations

CT scan of RE orbit showed a large thick-walled bleb (24.5×16.5 mm) in the superotemporal quadrant (figure 2A) with posteriorly displaced implant seen as a hyper dense structure. The implant plate was adherent to the superior bleb wall (figure 2B) and the posterior border of the cyst was very close to the optic nerve,; however, there was no impingement on the nerve.

Figure 2.

(A) Coronal CT Scan showing superotemporal cystic bleb and implant plate adherent to the cyst wall (red arrow) with downward displacement of the eye ball. (B) Axial CT scan showing a large cystic bleb superotemporally and posteriorly displaced implant.

Differential diagnosis

We considered a differential diagnosis of a large encysted bleb or an orbital tumour. On CT scan, the cyst had a smooth wall with echolucent cyst, implant was displaced posteriorly and pushed towards the superior cyst wall, proptosis with globe displaced inferiorly and medially was noted. So, a diagnosis of RE proptosis secondary to large fluid-filled cyst with a posteriorly dislocated implant was made.

Treatment

In view of severe proptosis and proximity of the implant to the optic nerve, trans-conjunctival incision of the cyst with marsupialisation and implant removal was planned along with lens aspiration. Intraoperatively, we found intact scleral patch graft and the tube track; however, the tube was retracted and folded within the cyst along with the detached implant. The AGV was explanted and the tube tract was covered with the patch graft and was sutured. Postoperatively, his proptosis decreased with improvement in alignment and extra ocular motility (figure 3A). The IOP in his RE was uncontrolled despite maximum tolerated medical therapy and hence a non-flow restrictive implant, Aurolab aqueous drainage implant (AADI) was implanted inferotemporally.

Figure 3.

(A) Clinical picture showing resolved proptosis after explantation of the drainage implant. (B) Clear descemets stripping endothelial keratoplasty (DSEK) graft, tube in place (arrow) with inferotemporal bleb.

Outcome and follow-up

Post AADI implantation, IOP was brought under control (10 mm of Hg) with one topical antiglaucoma medication. He later underwent Descemets stripping endothelial keratoplasty in both eyes (BE). At the last visit, he had clear grafts with tube implant with well-formed bleb (figure 3B) he was seeing 20/200 binocularly.

Laboratory evaluation

We tested the AGV flow properties of explanted device invitro as described by the FDA.⁴ The device was placed in a saline bath and was connected to an open manometer, a digital manometer and an infusion pump (figure 4). Saline was infused into the system at a rate of 3 µL/min for 24 hours. Digital manometer readings were recorded at 4 Hz using computerised data logging. The pressure curves were plotted against time in MATLAB (Mathworks, Natick, Massachusetts, USA). The maximum and minimum pressures obtained were defined as the opening and closing pressures respectively, which was found to be normal at 11 mm Hg and 8 mm Hg respectively in our explanted device. However, we noted excess fluid collection at the junction of the tube and the valve chamber anteriorly. We examined the valve complex after dislodging it from the silicone case. On injecting the fluid through the tube, we noted two fluid jets, one directed posteriorly (normal flow) and one directed anteriorly (figure 5) towards the tube which was abnormal. This was noted on repeated testing confirming deranged valve function.

Figure 4.

Experimental lab setup for testing the Ahmed glaucoma valve, showing the infusion pump, liquid column manometer, the digital manometer along with microscope and the test cell.

Figure 5.

Picture showing leakage of blue dye anteriorly. Injection of red dye showing anteriorly directed jet of fluid (shown in arrows) after removing the polypropylene case.

Discussion

Orbital complications due to aqueous drainage implants are rare with only a few case reports in literature. Marcet et al⁵ reported two cases of proptosis post AGV implantation, one due to escape of perfluoropropane gas through the tube into the orbit and another due to orbital cellulitis. An encapsulated bleb leading to a giant reservoir formation causing proptosis after AGV implant has been reported by both Jeon et al⁶ and Alonzo et al.⁷ Neither of them were associated with dislocation of the implant.

Demirkilinc Biler et al⁴ reported a similar case of 2-year-old child who underwent RE AGV implantation for aphakic glaucoma, presented with downward dystopia and motility limitation. The tube of AGV was not observed in the anterior chamber. MRI orbit showed a 19×16 mm cystic lesion in the extraconal space that displaced the globe downwards and the implant was seen at the periphery of the cyst. Total cyst excision along with the implant through an anterior transcutaneous orbitotomy approach using Stallard Wright incision was done. Hisopathological examination of the excised specimen revealed an epithelial cyst, hence they hypothesised that the cyst could have been an epithelial inclusion cyst formed from the epithelial remnants captured by the sutures/suture needles during the primary surgery. The implant was found to be detached from the globe similar to our case. In our opinion, we followed a simpler and a less invasive approach of cyst incision with marsupialisation without any postoperative recurrence. Since, the elevated IOP after AGV explantation could not be controlled despite four antiglaucoma medications, a non-valved glaucoma drainage device (AADI) was implanted, which has shown good IOP control following failed AGV cases, as in our case.⁸

We hypothesise that the dysfunctional valve could be the possible cause for the dislocation of the implant with a giant reservoir leading to proptosis. On closer examination of the implant, one of the eyelets was torn with no suture and the other eyelet was intact with a loop prolene suture attached to it. The excess pressure by the fluid accumulated under the implant could have displaced the implant superiorly towards the cyst wall and the traction would have resulted in displacement of the implant from the sclera with suture avulsion and tear in the eyelet. We also closely examined the implant for possible damage during the surgical procedure and found toothed forceps marks noted on the end plate of the implant but there was no leak noted at these sites.

With the above evidence, we hypothesise that the anteriorly directed jet of fluid due to dysfunctional valve mechanism could have led to anterior and inferior fluid accumulation rather than posterior drainage. Absence of physical damage along the leakage site also indicates that it was not caused during surgical procedure. We do not have the evidence of whether this leakage was present at the time of implantation and was missed during the priming of the valve. However, the possibility of damage to the implant during the surgery cannot be ruled out.

In conclusion, proptosis with dislocation of the implant though a rare complication can occur after AGV implantation. Orbital imaging plays an important role in the diagnosis and management. To the best of our knowledge, this is the first report studying the explanted implant in such a case and we suggest that abnormally leaking implant can lead to such serious but rare complication and the surgeon should be alert for such a malfunction at the time of priming. If defective, it is better to replace the implant with a new one to avoid serious complications.

Patient’s perspective.

Patient’s father: I was worried about sudden bulging of eyeball after surgery and rushed my son to the emergency. They told that nerve might be affected and after examination and CT scan, doctors told us that it is due to a swelling caused by the implant and reaching close to the optic nerve. Immediate surgery with implant removal was done. We felt very stressed as eye pressure was not getting controlled after implant removal but doctors gave us hope and luckily second implant was working well. Further surgery to clear his cornea was done. Today his vision is better and eye pressures are under control.

Learning points.

• Extraocular motility should be checked in each visit following glaucoma drainage device implantation.

• Imaging is mandatory if patient presents with orbital signs such as proptosis in order to diagnose the aetiology and the extent of the lesion, adding valuable information for appropriate management.

• Our case highlights the importance of actively checking for any anomalous flow while priming the valve in an Ahmed glaucoma valve.

• Cyst incision with marsupialisation is a simple, effective and less invasive approach in the presence of large orbital cyst in case of displaced implant.

• Non-valved implants might give good results in cases where valved implants are associated with large cysts.