While the rate of intraocular lens (IOL) dislocation is low, it is a significant potential complication of cataract surgery. We describe the key factors to consider before undergoing IOL refixation, as well as common techniques for the explantation of an IOL and fixation of a displaced one-piece IOL. Overall, fixation of dislocated IOLs is a safe and effective alternative to removal and replacement with secondary IOL insertion and has the added benefit of maintaining the optical properties of the initial lens, such as toricity and multifocality.
Key points
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Intraocular lens dislocation is a potential complication of cataract surgery that can be managed with observation if mild, or intraocular lens repositioning or exchange if symptomatic.
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Common indications for surgical intervention include decreased vision, monocular diplopia, halos, uveitis, glaucoma, and hyphema syndrome.
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Intraocular lens removal techniques include hold/fold, roll, and sectioning. The technique used depends heavily on the material of the intraocular lens.
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Single-piece intraocular lens repositioning techniques include the lasso technique and the belt loop technique.
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Studies suggest comparable visual outcomes for repositioning and exchange, with potential complications and considerations for each method.
Video content accompanies this article at http://www.advancesinophthalmology.com .
Introduction
While cataract surgery with intraocular lens (IOL) insertion is a safe and effective surgical intervention, IOL dislocation is an infrequent, yet significant complication. Reported rates of IOL dislocation range from 0.05% to 1.7% [ ]. With an aging population expected to result in an increased number of cataract extractions, the incidence of IOL dislocation is anticipated to rise in the future.
The malposition of an IOL occurs over a spectrum. Decentration refers to the misalignment of the lens from the visual axis without zonular or capsular instability. Subluxation refers to the partial loss of zonular or capsular support. Dislocation refers to the complete loss of zonular or capsular support and can occur with the lens remaining either within or outside the capsular bag. Dislocation can occur with the lens dislocating into either the anterior or posterior chamber.
IOL dislocation commonly is related to the integrity of the capsular bag and zonules; therefore, conditions that affect the stability of these structures are considered risk factors. Predisposing conditions include pseudoexfoliation syndrome, prior vitreoretinal surgery, history of trauma, history of uveitis, retinitis pigmentosa, surgical complications (such as zonular dehiscence or posterior capsule tear), mature cataract, long axial length, and primary angle-closure glaucoma [ ].
IOL dislocation may present asymptomatically when mild or in an eye with poor visual potential. Alternatively, they may be accompanied by a decline in visual acuity due to lens malposition. Moreover, dislocation can lead to increased lens tilt and higher-order aberrations, resulting in decreased contrast sensitivity, dysphotopsias, monocular diplopia, polyopia, glare, and halos [ , ]. Asymmetric intraocular lenses, such as multifocal lenses, are particularly sensitive to IOL decentration [ ].
Indications
IOL repositioning is indicated for a number of reasons, including inflammation, cystoid macular edema (CME), uncontrolled intraocular pressure, uveitis glaucoma and hyphema syndrome (UGH), intraocular lens dislocation, subluxation, and unsatisfactory refractive outcomes such as a refractive surprise, dysphotopsias, or refractive instability.
In one study, the most common reasons for surgically managing dislocated IOLs were decreased visual acuity, monocular diplopia, and halos [ ]. Another study of 48 cases of IOL repositioning revealed that 58% of the procedures were performed due to IOL dislocation, 20.8% for corneal decompensation, and 6.3% for IOL degeneration [ ].
In a 10-year retrospective review, 53 out of 249 patients referred for evaluation for IOL repositioning or exchange presented with UGH [ ]. While UGH rates have significantly decreased with the widespread adoption of posterior chamber IOLs (PCIOL) compared with anterior chamber IOL’s (ACIOL) and advancements in materials; UGH can still occur with PCIOLs. Surgical management of UGH with lens repositioning or exchange has demonstrated high efficacy, with one study reporting the resolution of uveitis and hyphema in all surgical cases. Additionally, there was a significant reduction in IOP and in the number of pressure-lowering therapies used by patients [ ].
Assessment
Begin by evaluating signs of complex primary cataract extraction and IOL implantation such as zonular loss, vitreous presence in the anterior chamber (AC), or disruption in the posterior capsule. Assess patients in both upright and supine positions to determine the extent of lens instability, differentiating between dislocation and decentration. Evaluate the support for a secondary IOL or repositioned IOL by assessing the anterior and posterior capsules. Patients with capsular bag damage may be at risk of the lens dislocating out of the capsule posteriorly. When the posterior capsule is compromised in the setting of YAG capsulectomy, a secondary lens may be placed within the residual capsule or in the sulcus with optic capture. Regardless of lens placement, when planning for lens exchange with an open posterior capsule, the surgeon will need to plan for anterior vitrectomy. Look for signs of pseudoexfoliation syndrome, such as pseudoexfoliative material on the pupillary margin, transillumination defects, poor pupillary dilation, phacodonesis, or Sampaolesi line on gonioscopy. Pupil abnormalities may suggest prior use of iris hooks or Malyugin rings, raising suspicion for weak structures. Severe zonular instability may lead to the entire lens-capsule complex dislocating into the vitreous, eliminating the possibility of the sulcus or capsular placement of a secondary lens.
Imaging for a patient being considered for lens exchange may include macular OCT to assess for CME or B-scan ultrasonography to assess the status of the retina if not readily visualized. Ultrasound biomicroscopy is a diagnostic method to visualize the anterior segment of the eye and can localize the IOL optic and determine the position of the IOL haptics [ , ]. This is especially helpful in patients with poor pupillary dilation and in cases where the peripheral portions of the haptics are hidden behind the iris [ ].
Access to the operative report, implant sheet, and postoperative course, including any additional procedures performed such as YAG capsulotomy, can supplement the patient’s examination findings. While intraoperative surprises may be unavoidable, a meticulous patient history and examination can provide valuable clues to prior procedures and complications.
Finally, as these patients are seeking care for complications and unsatisfactory outcomes after their primary surgery, clinicians should have lengthy discussions regarding adverse outcomes in the secondary surgery such as the lens falling posterior before or during surgery, damage to the cornea, and corneal decompensation, induced astigmatism, inflammation, UGH or CME.
Management
Once a misaligned IOL is identified, the clinician must determine a plan with the patient. Mild pseudophacodonesis or lens decentration may be monitored closely and treated with refraction [ ]. Significant changes to visual acuity that cannot be improved with refraction or additional ocular sequelae of lens dislocation such as UGH, glaucoma, or retinal detachment may require surgical management.
Once the decision to operate has been made, the surgeon must decide whether to perform lens repositioning of the current IOL, or removal and replacement with a new IOL. This decision is influenced by the remaining support structures and the type of IOL present within the eye.
Intraocular Lens Mobilization
The first step in all IOL exchanges and many IOL repositioning procedures is to fully mobilize the dislocated IOL. Considerations for mobilizing the IOL are highly dependent on the IOL location within the eye.
Single-piece IOLs in the posterior chamber may form significant fibrotic adhesions between the IOL and capsular bag that must be completely released before mobilizing the lens. One must avoid the disruption of the zonules or traction on the vitreous. Careful dissection can leave the posterior capsule intact and allow for safe in-the-bag IOL exchange.
Our preferred method is to use a cyclodialysis spatula and Kuglen Hook to aid in the visualization of the IOL, haptics, and anterior capsule. Care must be taken not to disrupt the anterior capsule if one is planning for sulcus IOL placement. A cohesive ophthalmic viscoelastic device (OVD) is used to free up the lens from the scarred capsule. A pocket is then created between the IOL and the capsule with a 25-gauge needle. This is done by paying particular attention to fibrosis at the haptic optic junction, terminal bulb, and the area between the anterior and posterior capsule leaflets. In the event of significant phimosis of the anterior capsule which restricts the mobilization of the lens from the capsular bag, enlargement of the capsulorhexis, or radial relaxing capsulotomies may be necessary. It is critical to achieve free rotation of the lens before attempting elevation out of the capsular bag. If the IOL is unable to be mobilized, haptic amputation of one or both haptics may be required. These amputated haptics may be left within the capsular bag, allowing for the removal of the lens optic [ ].
Alternatively, 3-piece IOLs tend to be easily freed from the capsular bag because the haptics do not tend to form the fibrous tissue that is more often observed with single-piece IOLs. Care must be taken to avoid the haptics abutting the posterior capsule and cornea during removal [ ].
In contrast to lenses within the capsular bag, sulcus lenses frequently have minimal fibrotic attachments and generally can be easily mobilized [ ].
Lenses affixed to the anterior iris surface (iris claw lenses) must be disengaged before removal. This can be accomplished by stabilizing the lens with forceps and depressing the enclevated iris tissue [ ].
Over time, ACIOLs can form fibrous adhesions around their haptics, which may be visible on gonioscopy. The adhesions may be broken by rotating the IOL clockwise. Forced rotation or extraction before freeing the fibrous adhesions can lead to iridodialysis and hyphema. Haptic amputation may be necessary if the adhesions cannot be safely broken. Placement of viscoelastic in front of and behind the lens before manipulation protects the cornea and prevents vitreous prolapse, as many of these lenses are inserted due to a violated capsule [ ].
Lens Removal
Lens removal techniques can be influenced by several factors, such as the location of the lens, lens material, and the presence of posterior capsulotomy.
Lens Material
Lens materials vary in terms of whether they are re-foldable, or able to be cut within the eye, thereby impacting which techniques may be used during a lens removal.
Polymethyl methacrylate (PMMA) was the first material used for IOLs but has been made nearly obsolete given newer foldable materials. The material cannot be cut inside the eye. Just as with implantation, explantation of a PMMA lens requires a large incision of approximately 6 mm, which would ideally mean using a scleral tunnel. This can be done inferiorly to preserve superior conjunctiva for patients with glaucoma [ ].
Acrylic lenses are currently the most used material in PCIOLs. In the event of removal, they can be explanted by a multitude of techniques given their soft and flexible structure including sectioning or folding.
Silicone lenses resist refolding intraocularly as they are slippery and thicker in the center, and therefore are best removed through one of the various sectioning techniques.
Lens Removal Techniques
If it is determined that a lens exchange is required, the following techniques may be considered depending on the IOL’s accessibility, and material.
Vitrectomy Assisted
Vitrectomy-assisted lens exchange may be required in cases whereby the IOL has completely dislocated into the posterior chamber. In these cases, a thorough vitrectomy is required to avoid traction on the vitreous or retina. Then the IOL can either be brought into the AC and removed via one of the techniques described later in discussion, or via the enlargement of a pars plana sclerotomy [ ].
Hold/Fold
Hold/Fold technique requires a cross-action lens folder and a cyclodialysis spatula. The cyclodialysis spatula goes under the lens, while the lens folder goes over the lens. The lens is then folded down over the spatula, rotated 90°, and then explanted. The technique can only be used on foldable lenses such as acrylic, and on average requires a 3.5 mm corneal incision, larger than those required with sectioning techniques, but avoids tissue trauma from the sharp edges of a cut lens [ , ].
Roll
The roll, also known as the twist and out technique, is a great technique for single-piece lenses. This technique also requires the presence of a foldable lens type, such as acrylic. This requires tying forceps and a cyclodialysis spatula. The cyclodialysis spatula is placed on top of the IOL and protects the endothelium as the soft lens is rolled into a taco shape. The lens will then glide out of a 2.2 mm incision [ , ]. ( [CR] and [CR] )
Sectioning
Sectioning of the lens in half, or “pac-man style” is a great option for most lenses asides from PMMA lenses, which are too hard to section intraocularly. Before cutting the lens, place the OVD under the IOL to create space between the lens and the posterior capsule. At this point, the lens can be fully sectioned and removed piecemeal, often requiring an approximately 3.0 mm incision, or cut “pac-man style,” whereby the lens is bisected ¾ of the way through [ ]. This creates a hinge by which the surgeon can pull out the first half of the IOL through the incision, then the second half can be rotated out of the wound. The advantage of this technique is that a smaller incision can be made, typically slightly wider than a 2.4 mm main wound for cataract surgery. Additionally, there are no small intraocular lens fragments that may more readily fall through an open posterior capsule. The creation of a posterior capsule tear during the lens bisecting process is a risk associated with all sectioning techniques ( Fig. 1 ).
