This article reports a series of four complicated cataract surgery cases referred to one of the authors in which a flexible open-loop polymethylmethacrylate (PMMA) Kelman Multiflex anterior chamber IOL was placed in an inverted configuration. In all cases, the inverted placement resulted in ocular complications, including chronic iritis, cystoid macular edema (CME), pupil capture, iris adhesions and corneal decompensation. The authors conclude that surgeons inserting the Kelman Multiflex anterior chamber IOL should ensure that it is correctly oriented so that the optic vaults anteriorly and not posteriorly.
They believe that this is the first reported series of patients with inverted-configuration anterior chamber IOL implantation, which they have named, "upside-down lens syndrome." The authors say that the complications that developed in each case were directly attributable at least in part to the broad posterior contact of the optic against the iris and the abnormally anterior placement of the haptics against the peripheral cornea. Peripheral iridectomies had been performed in all of the cases, and no cases had evidence of pupillary block.
CME was documented by ocular coherence tomography in two cases. In one patient, iris capture of the optic occurred, which prompted an additional surgical procedure to reposition the implant and to lyse iris synechiae; however, the inverted orientation of the IOL was not recognized or addressed, which led to eventual corneal decompensation. Pseudophakic bullous keratopathy occurred in three cases. Surgical intervention was necessary in each case, consisting of penetrating keratoplasty, corneal cautery and endothelial keratoplasty.
The Kelman Multiflex anterior chamber IOL is specifically designed to be placed in the correct orientation (each haptic forming the bottom half of a reverse "Z"), as diagrammed on the lens packaging. The optic is vaulted forward so that iris chafing is minimized, adequate clearance away from the corneal endothelium is provided and good fixation stability is achieved with the haptics resting in the angle, adjacent to the iris root and away from the peripheral cornea. However, the authors say that chronic chafing of the iris against the IOL can lead to chronic uveitis and may precipitate or exacerbate CME. Also the haptics in an inverted anterior chamber IOL are unable to properly rest on the iris root and can migrate anteriorly and contact the peripheral corneal endothelium, resulting in endothelial cell loss and corneal edema.
The authors speculate that the relatively low frequency of anterior chamber implantation and surgeons' resulting lack of familiarity with the procedure may increase the risk of incorrect placement. They conclude that there are several measures that surgeons can take in order to avoid inadvertent upside-down placement of this IOL, including inspecting the haptic configuration to verify that it matches the diagram on the exterior packaging or in the package insert, confirming the forward vault of the lens optic when viewed in side profile and compressing the haptics and observing the further forward vaulting of the optic when viewed in side profile. If a lens is placed in an inverted configuration, they say that early recognition is vital, and timely IOL exchange or proper repositioning of the existing lens should be considered to prevent adverse clinical outcomes.