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Posterior IOL-Luxation: Characteristics, Surgical Approach and Current Treatment Controversies

Silvia Bopp

Bremen, Germany

Introduction: Posterior dislocation of IOLs in the era of phaco/in-the-bag implantation is a rare complication. The leading symptom is sudden visual loss due to optic "aphakia". Treatment is recommended firstly for the patient's visual rehabilitation and secondly to prevent late complications. Although clear scientific data is lacking, it is generally assumed, that the mobile intravitreal foreign body can lead to cystoid macular edema and late retinal detachment. On the other hand, removal of a dislocated IOL is a difficult surgical procedure and necessitates anterior and posterior segment techniques. Postoperative retinal detachment is reported in 5-35%. Since posterior segment complications in case of inadequately performed IOL-repositioning or IOL-exchange is expected to be far higher than leaving the IOL in place and current clinic data did not prove significant complications in eyes with long-term dislocated IOLs, various treatment options are worth considering: 1. No surgical revision and visual rehabilitation by glasses or contact lenses. 2. No surgical revision, but visual rehabilitation by a secondary IOL-implant. 3. Surgical revision with IOL-repositioning or IOL-removal/-exchange. For addressing this dilemma, we analyzed our clinical database and report on 40 eyes/40 patients with complete IOL-dislocation that were operated on in our clinic between 1994 and 2001.

Patients/Methods: The data is based on a detailed ophthalmologic history, documentation about previous surgery, complete pre- and postop ophthalmologic examination and OR records. Minimum follow-up after revision surgery was 4 weeks.
Revision surgery included vitrectomy with mobilization of the IOL and their haptics that were always entangled with vitreous fibres. Additional limbal incisions were prepared: limbal paracentesis for introduction of various spatulas or hooks and, in case of IOL-exchange, a scleral or limbal tunnel according to the size of the IOL. Once the IOL was retrieved and elevated into the pupillary area, various instruments (forceps, spatulas, hooks) were needed to hold and maneuver the IOL toward the incision. Optics must be switched from indirect BIOM-view to direct microscope view. Sclerotomy and limbal incisions were used for bimanual manipulation. Generous use of viscoelastics was necessary to protect the corneal endothelium. Infusion pressure had to be as low as to prevent collapse of the vitrectomized eye and maintain the eye's shape, but not wash out all viscoelastic material. After removal of the IOL, implantation of another appropriate IOL into the anterior or posterior chamber was performed. In case of IOL-revision (sulcus-type) the present IOL was maneuvered with or without suturing into the ciliary sulcus. In one eye with two IOLs (dislocated silicone IOL and sulcusfixated acrylic IOL), the luxated one was cut into little pieces and removed via the sclerotomies to avoid taking off both lenses and additional anterior segment trauma. Careful fundus examination with deep indentation was mandatory at the end of surgery. In case of any retinal break or beginning detachment, coagulation therapy and gas tamponade were performed accordingly. Various situations will be illustrated by video sequences.

Results: 80% of patients were referred to our surgical center, the remainder were own cases. Posterior IOL-luxation had occurred intraoperatively during complicated cataract surgery with capsular or zonular problems and inappropriate IOL-implantation (unsuitable design or wrong size, improper location, lack of sufficient capsular support) (=5 eyes). In most cases, however, the IOL had dropped during the postoperative phase (interval 2 days to 5 years). We found one or more of the following predisposing factors: o previous complicated surgery as mentioned above (also: one eye with capsular defect and severe capsular shrinkage and one patient showing autoaggressive behavior), o conditions that lead to progressive zonular weakness (later additional vitrectomy, high myopia, blunt trauma) and o spontaneous luxation of silicone disc IOLs after YAG-capsulotomy (total of 35eyes).
In general, preexisting in-the-bag IOLs (total diameter <12mm, with loop and plate hapics) had to be removed, since replacement into the capsular bag was not possible and precapsular fixation seemed unstable. It is noteworthy that several IOLs present were in-the-bag types, but had been implanted into the sulcus. Dislocated sulcus-type IOLs were either reimplanted (±suturing) or exchanged by an AC-IOL. One IOL had a haptic that had broken during previous surgery.
Decision parameters for any technique mentioned above based on the capsular support, intraoperative pupil size and possible contraindications against an AC-IOL. Revision surgery with IOL-provision was achieved all, but 3 eyes (one eye: high myopia, no significant refraction error and two eyes: compromised anterior segment, secondary IOL-implantation later). Intraoperatively 5 eyes showed preexisting or new retinal tears (2 eyes with peripheral detachment) that were treated with laser or cryo and gas tamponade. Postoperative posterior segment complications, e.g. retinal detachment did not occur.

Discussion/Conclusions:
Prevention: Several cases had more than one risk factor for IOL-dislocation, e.g. complicated cataract surgery & an unsuitalbe IOL-type & inappropriate implantation site. Accordingly, posterior IOL-luxation could have been avoided in some eyes. The cataract surgeon should carefully consider the individual anatomic situation (presence/absence or amount of capsular support) and the availability of an appropriate IOL-type (stand-by IOL) during complicated cataract. For most situations, in-the-bag IOLs are not indicated. If a suitable IOL is not at hand, we suggest secondary IOL-implantation. However, there are no known preventive measurements of late IOL-dislocation in other eyes (progressive zonulolysis, zonular trauma and the disappearance of disc lenses after YAG capsulotomy).
Treatment: Decision parameters for IOL-explantation/exchange and IOL-repositioning largely depend on the capsule situation and the size/design of the IOL present. Basically, surgical management includes pars plana techniques with full vitreoretinal equipment available combined with anterior segment access. Being aware of the fact that the dislocated IOL is big rigid intra-vitreal foreign body, the surgeon's experience and skill are important factors to keep complications low. For this reason, implantation of a second IOL in an eye with posterior dislocated IOL is legally judged an error in Germany. However, scientific data has shown that long-term complications of dislocated IOLs with/without a second IOL are relatively low. These are reasonable options, if there is no qualified vitreoretinal service available.