Management of recurrent aqueous misdirection by anterior segment surgeon after failed pars plana posterior vitrectomy.

Aqueous misdirection (AM) is a dreaded complication, but fortunately quite rare. It usually occurs after intervention for angle closure glaucoma. When pharmacotherapy and/or laser interventions are unsuccessful, then the surgical management hitherto most commonly undertaken is pars plana posterior vitrectomy. We describe the management of recurrent AM via the anterior route, when it occurred following relapse as pars plana posterior vitrectomy failed to result in long-term normalization of anterior chamber and intraocular pressure. Anterior vitrector with anterior vitrectomy settings was used by a glaucoma specialist to carry out the procedure.

Aqueous misdirection (AM) is a rare complication following intervention for angle closure glaucoma. AM is believed to occur at the lens-zonule-iris-ciliary body-hyaloid interface, complete disruption of which is the key to normalization of the anterior segment. AM, however, may recur despite an optimal core vitrectomy.[12] Herein we report a case of a recurrent AM managed by anterior vitrectomy by the clear corneal incision.

Case Report

Our 58-year-old patient had primary angle closure glaucoma (PACG) for which she had phacotrabeculectomy in the left eye elsewhere. One month following her surgery, she developed aqueous misdirection (AM). For resolution of AM, she underwent a pars plana posterior vitrectomy (PPV) and Ahmed glaucoma valve (AGV), also elsewhere.

She presented to us 6 weeks after PPV with count fingers vision, a flat anterior chamber (AC), corneal edema along with folds in Descemet's membrane, pigmentary membrane over pupil, tube barely visible in the AC, and two patent peripheral iridectomy (PI) with an intraocular pressure (IOP) of 26 mmHg on three anti-glaucoma medications (AGM) and cycloplegics. There was no view of the fundus, and choroidal detachment was excluded with a B-scan.

Fellow left eye was hypermetropic and had best corrected visual acuity (BCVA) of 20/20. AC was shallow with a patent PI and cataract. Disc was normal.

Diagnosis of recurrent AM was made in the left eye, and she had a Yag hyaloidotomy following which AC deepened marginally only [Fig. 1]. She was scheduled for Irido-Zonulo-Hyaloido-Vitrectomy (IZHV) through preexisting PI soon thereafter, as corneal decompensation was a distinct likelihood.

Figure 1

Left: White arrow indicates only marginal deepening of anterior chamber following laser hyaloidotomy. Right: Presentation of eye with flat anterior chamber prior to laser hyaloidotomy in eye with recurrent aqueous misdirection after failed pars plana posterior vitrectomy

Pre-operatively, patient received mannitol in appropriate dose for vitreous deturgescence.

In the operating room, under sterile conditions, a paracentesis was made at 9:00 o’clock. Entry into AC was difficult and was aided with viscoelastics.

Iris repositer was used for synechiolysis and a 20-G vitrector was used to cut the pigmented pupillary membrane first and enlarge the PI at 2:00 o’clock to aid ensuing steps.

A second paracentesis was made at 3:00 o’clock.

A corneal incision was then made, overlying the preexisting PI [Fig. 2a] at 10:00 o’clock and the vitrector introduced almost vertically, initially facing the surgeon to enlarge the iridectomy and perform a zonulectomy [Fig. 2b].

Figure 2

Schematic of Irido-Zonulo-Hyaloido-Vitrectomy and primary posterior capsulectomy. (a) White arrow indicates the corneal incision made overlying preexisting peripheral iridectomy (iridectomy indicated by the black arrow). (b) Anterior vitrector introduced through the corneal incision, vitrector initially facing the surgeon posteriorly (indicated by the white arrow)—for enlargement of preexisting iridectomy and performance of zonulectomy. (c) Anterior vitrector rotated to face anteriorly (indicated by the white arrow) for hyaloidectomy and primary posterior capsulectomy also done (indicated by the black arrow)

A 20-G bi-manual vitrector was used, typically with a cut rate of 600-800 and low-to-moderate flow. Following this, the vitrector was slowly rotated to face anteriorly while performing a hyaloidectomy and a primary posterior capsulectomy (PPC) [Fig. 2c]. AC became deep and stable; it soon became apparent that the tube was very superficial, and this was re-sited to avoid corneal decompensation.

Filtered air was injected and AC was well formed at the end of the surgery. There were no intra-operative complications associated with the procedure.

Post-operatively, the patient was advised topical antibiotics for 1 week, topical atropine for 3 weeks, and topical prednisolone 1% eye drops every 2 hr and then tapering over the next 6 to 8 weeks. She had deep AC [Fig. 3] till last follow-up of more than 22 months; recovery of BCVA to 20/30, clear cornea, tube well-positioned in AC and controlled IOP without any medication were the other clinical features. Disc had an inferior notch with a correct detection rate (CDR) of 0.8 and corresponding superior arcuate field defect, involving fixation on 10-2.

Figure 3

Left: Patient's eye on presentation with recurrent aqueous misdirection after failed PPV and pre-IZHV. Right: Deep anterior chamber, clear cornea, and well-positioned tube in AC 3 months post IZHV

She did not have any post-operative sequelae related to the procedure (neither retinal break or detachment nor any subluxation/dislocation of intraocular lens (IOL) implant).

Discussion

AM is also known as malignant glaucoma, ciliary block glaucoma, among others. The pathophysiologic mechanism of AM is ill-understood; however, it is commonly believed to occur at the lens-zonule-iris-ciliary body-hyaloid interface, complete disruption of which is the key to normalization of anterior segment. This may not always be possible with core vitrectomy as recurrence of AM is not unknown after PPV and has been reported by several authors.[12] Indeed, Debrouwere et al.[1] favored a radical posterior vitrectomy with an iridectomy–zonulectomy tunnel, to prevent relapse. In their relatively large series, they encountered recurrent AM in 75% of the cases following core vitrectomy, perhaps a reflection of incomplete hyaloidectomy. Lois et al.[3] and Zarnowski et al.[4] have described a very effective anterior segment approach in the form of IZHV for treatment of pseudophakic AM. We extrapolated this technique and adapted it in recurrent AM in a pseudophake with success, where PPV failed to result in long-lasting normalization of AC. We believe that by tweaking the procedure of IZHV with the addition of PPC, we achieved complete anterior hyaloidectomy. In this case, this procedure was facilitated by the pseudophakic status of the eye. Hence, should AM occur in a phakic eye post-filtration surgery, lens extraction and in-the-bag IOL are strongly recommended. Our patient's eye also had a long-term control of IOP, made possible by the presence of a functioning AGV. However, in long-standing cases of AM, where synechiae have formed, the surgeon needs to plan revision of, or re-do, filtration surgery along with IZHV and PPC for long-term control of IOP along with normalization of AC depth.

This relatively simple and cost-effective technique performed with an anterior vitrector by an anterior segment surgeon resulted in prompt reversal of relapsed AM with its sustained long-term resolution and control of IOP.

Conclusion

To conclude, for complete resolution in AM, we strongly recommend a complete anterior debulking of hyaloid and disruption of the hyaloid face, made possible by use of an anterior vitrector using anterior vitrectomy settings, thereby reducing burden on the resources, skills, and potential complications of a vitreo-retinal procedure.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.