Acute aqueous misdirection syndrome: Pathophysiology and management

Abstract

We appreciate Lau et al.1 formally describing the syndrome of acute anterior chamber shallowing and increase of intraocular pressure with no choroidal effusion. However, we believe this syndrome has been described under different names, including infusion misdirection syndrome, capsular block, intraoperative fluid misdirection, and subcapsular fluid entrapment.2,A The pathophysiology of the syndrome is based on the inappropriate “movement of the balanced salt solution via the zonular fibers.”1 Thus, we suggest that it should be called acute aqueous misdirection syndrome as this better describes the nature of the syndrome rather than one of its signs. Aqueous misdirection syndrome, also called malignant glaucoma based on similar pathophysiology of trapping fluid in the posterior segment, is characterized by a similar clinical picture but usually occurs from a few days to months or years after the initial surgery.3 This could be termed chronic aqueous misdirection syndrome. We agree that acute aqueous misdirection syndrome is probably underreported; anecdotally, most surgeons admit to having experienced it occasionally. The common theme is that it occurs toward the end of irrigation/aspiration (I/A), making the completion of I/A or the insertion of an intraocular lens impossible because of a flat anterior chamber. Irrigating fluid is known to be able to travel through intact zonular fibers into Berger space. This may occur rapidly toward the end of I/A, explaining the occurrence of the syndrome. The unconventional use of the residual cortical fiber irrigation maneuver in the authors’ practice may account for the relatively high frequency with which the acute aqueous misdirection syndrome is encountered. The use a of a straight transconjunctival transscleral needle puncture of the pars plana with aspiration of retrocapsular liquid poses some risks, including postoperative hypotony and increased risk for endophthalmitis. Aspiration of fluid using a needle from the posterior segment of the eye risks engaging vitreous, causing retinal traction and risking retinal tear formation. There is also the chance of inadvertently engaging the posterior capsule. We suggest that when faced with acute aqueous misdirection syndrome, it would be preferable to use a small gauge trocar/cannula vitrectomy cutter (23-, 25-, or 27-gauge). The incision in the pars plana should be made after displacing the conjunctiva and then fashioning a 2-step beveled incision, as is modern practice for pars plana entries.4 The cutter can then remove retrocapsular fluid using a high cut rate; if any vitreous were engaged, there would be negligible retinal traction. It behooves us to absorb the lessons learned by our posterior segment colleagues about a decade ago.