History. Imaging Studies

History

History findings related to IOL dislocation may include the following:

Complications during cataract surgery (posterior capsular rupture, zonular dialysis) History of Nd: YAG capsulotomy

History of ocular trauma Symptoms

The most common presenting complaint of a decentered IOL is unwanted optical images caused by either a centering hole or the edge of the optic within the pupil.

Patients may complain of decreased vision, edge glare, diplopia, streaks of light, haloes, photosensitivity, and ghost images.

Although malposition of a PCIOL may reduce the quality of vision, it is less likely than malposition of an ACIOL to cause mechanical injury or inflammatory sequelae. Pain and red eye are more common complaints in patients with ACIOL decentration if there is inflammation as a consequence. A sudden loss of vision due to uncorrected aphakia, retinal detachment, cystoid macular edema, or vitreous hemorrhage occurs with dislocated IOL. If the IOL is mobile in the vitreous cavity, the patient may complain of unusual floaters or optical effects.

Physical

ACIOL decentration

In patients with ACIOL decentration, slit lamp examination and gonioscopy may reveal iris tuck, which can cause uveal inflammation.

The eye may be red and tender.

A peaked or oval pupil can be found.

Inappropriate ACIOL size may cause a mobile lens.

ACIOL malposition may produce ongoing mechanical trauma to the cornea, iris, ciliary body, or anterior chamber angle.

Chronic inflammation may lead to corneal endothelial cell loss, cystoid macular edema (CME), glaucoma, microhyphema, and pain.

PCIOL decentration

Visual acuity can be compromised by optical aberrations and refractive changes. Slit lamp examination usually does not reveal evidence of inflammation unless contact of a portion of the IOL with the cornea or vitreous prolapse is present.

Corneal edema from IOL or vitreous touch can be found. In these cases, CME may be a complication.

Vitreous traction can increase the risk of a retinal detachment, while vitreous to the wound can be implicated in endophthalmitis.

IOL dislocation

The posterior capsule usually has an obvious defect. Zonular dialysis may be present.

The IOL may be freely mobile in the vitreous cavity; it may be in apparent contact with the retina; or it may have one haptic attached to the posterior capsule, iris, or ciliary body.

Causes

IOL decentration may occur as a result of factors during the original surgery and lens implantation, or it may develop at a later time as a result of either outside forces, such as trauma, or internal forces related to capsular dynamics.

ACIOL decentration

Inadequate size: A lens that is too small may be too mobile and cause intermittent damage to the cornea and iris.

Improper placement during surgery: An improperly placed ACIOL may be associated with iris tuck and uveal inflammation and PAS.

Prolapse of a haptic into either wound or iridectomy: This usually requires repositioning at a different angle to avoid recurrences.

PCIOL decentration

The pathogenesis of PCIOL malposition may be related to a variety of locations of haptic fixation, to the forces of capsular contraction, or to a combined mechanism. In a study by Tappin et al, early decentration of the injected IOLs occurred in eyes without a continuous capsulorrhexis. In contrast, late decentration was due to subluxation associated with capsular fibrosis. [8]

Asymmetric haptic placement: Before the development of capsulorrhexis, it was common for the surgeon to place the inferior IOL haptic within the capsule, while releasing the superior haptic into the ciliary sulcus producing asymmetric haptic fixation. Because significant decentration was expected, PCIOLs had large optics (7 mm) and long length (13-14 mm).

Subsequent healing from capsular fusion and contraction potentially caused the inferior haptic to exert forces on the optic unopposed by forces from the superior haptic within the sulcus. Migration of the optic as a result is termed sunrise syndrome.

Inadequate zonular or capsular support: This can be due to posterior capsular rupture or zonular dialysis both of which are more prevalent in patients with pseudoexfoliation. A disruption of the superior zonules when the inferior haptic is in the bag and the superior haptic is through the disinsertion also causes a sunrise syndrome as contraction of the bag forces the superior haptic through the disinsertion. Inferior dislocation of a PCIOL through an unrecognized zonular dialysis is a serious malposition termed sunset syndrome and is usually clinically evident within the first 6 weeks after surgery. A tear in the anterior capsule may allow one or both IOL haptics to migrate out of the capsular bag under the forces of capsular contraction. This has been referred to as " pea-podding. "

Capsular contraction syndrome: Capsulorrhexis is a major surgical advance that contributes to long-term IOL stability and centration. Despite an intact capsulorrhexis, IOL decentration may still occur due to capsular contraction syndrome. Too small a capsulorrhexis has been implicated. Silicone-plate IOL design is particularly susceptible to the forces of capsular

contraction and may decenter, rotate, tilt, or buckle. A survey by Mamalis et al cited IOL decentration as the most frequent reason for plate-type silicone IOL removal. [9] Plate-design lenses have a smaller arc of contact with the capsular fornix, reducing anchoring forces that normally reduce potential for rotation and decentration.

Capsular fusion: An eccentric capsulorrhexis may allow one of its edges to be more peripheral than the optic in one area, with fusion developing, producing decentration away from the area of contact. A large, symmetric, round, central capsulorrhexis is recommended to reduce significant decentration.

Postoperative trauma

In general, the main cause of dislocation is lack of capsular support for the IOL. This may be caused by any of the following: Unrecognized posterior capsule rupture

Progressive zonular dehiscence: Patients with pseudoexfoliation syndrome are at risk of developing zonular dehiscence. Late in-the-bag IOL dislocation is associated with pseudoexfoliation in more than 50% of cases.

Silicone plate lenses deserve special attention. It is believed that progressive contraction of the capsular bag increases the tension on the IOL and causes it to bow posteriorly. Progressive contracture of the anterior capsulorrhexis opening (pursestring) may occur more commonly with silicone plate IOLs. Dehiscence anywhere in the capsular bag allows release of tension through expulsion of the implant. Silicone plate IOLs have been known to dislocate in the following situations:

Following an extension of a radial notch tear in the anterior capsular rim

Following a YAG capsulotomy, particularly if a large capsulotomy is made and if the haptics are placed asymmetrically or the IOL optics are too small; interval from YAG capsulotomy to dislocation ranges from immediately to many months

Following an equatorial capsular break from a YAG iridotomy

In a retrospective interventional case series, possible major predisposing factors for in-the-bag IOL dislocation were pseudoexfoliation, retinitis pigmentosa, prior vitrectomy, trauma, and a long axis. For out-of-the-bag dislocation, predisposing factors included secondary IOL implantation, surgical complications, mature cataract, and pseudoexfoliation.

Complications

IOL dislocations may lead to various postoperative complications, including rhegmatogenous retinal detachment, glaucoma, cystoid macular edema bullous keratopathy, and uveitis. [10, 11]

Workup

Imaging Studies

If a vitreous hemorrhage or severe corneal edema is present, B-scan ultrasonic imaging should be used to determine the position of the IOL and the presence or absence of retinal detachment.

Histologic Findings

Studies in cadaver eyes indicate that transscleral sutures must exit the sclera 0. 8 mm posterior to the limbus in the vertical meridian and 0. 46 mm posterior to the limbus in the horizontal meridian to be within the true ciliary sulcus.

Postmortem studies disclosed that scarring does not occur in the vicinity of the sutured IOL. The haptics are surrounded by a thin fibrous capsule at their attachment site. The transscleral portion of the suture is characterized by the lack of inflammation. In addition, the suture tip usually is exposed externally. If the fixation sutures were cut, the IOL would dislocate back into the vitreous cavity. It was concluded that the stability of the IOL was primarily a result of intact transscleral sutures and not fibrous encapsulation or ciliary sulcus placement of the haptics.

Treatment

Medical Care

Selection of treatment in the case of a decentered IOL should be based on the patient's symptoms, needs, and expectations.

Observation: In the absence of symptoms and no evidence of inflammatory sequelae, observation is an option. In the case of an ACIOL associated with a peaked or oval pupil, careful observation is warranted if there are no signs or symptoms of intraocular inflammation.

Miotics: If symptoms from a decentered PCIOL are infrequent and limited to evening, due to a dilated pupil, these patients may be treated conservatively by using a topical miotic such as pilocarpine 0. 5-1% qhs. A trial of miotic agents may be warranted prior to removing or repositioning an implant.

Observation may be recommended in dislocated IOLs if the following conditions are met: The IOL is not mobile.

There are no retinal complications.

The patient is satisfied with aphakic spectacle correction or contact lenses.

Surgical Care

When more severe and disabling symptoms or if inflammation is present with the potential for further complications in the future, treatment should include either repositioning, explanting, or exchanging the decentered IOL. [12] Selection of treatment is based on the patient's symptoms, visual needs, and expectations, and an assessment of which option is likely to provide the best long-term benefit with the least risk.

IOL reposition: An IOL may become decentered due to either insufficient zonular support or to irregular fibrosis of the posterior capsule. In the case of inadequate support, early in the postoperative period the surgeon may attempt to rotate the IOL surgically where there is clinical evidence of sufficient capsule and zonules to support the implant. A helpful maneuver is the bounce test where the optic is pushed gently toward each haptic to ensure spontaneous recentration.

IOL reposition with McCannel sutures: In some cases, repositioning may be supplemented by the use of trans-iris IOL fixation (McCannel) suture.

IOL explantation: Certain circumstances warrant removal of an IOL without secondary IOL implantation. This is determined on an individual basis and taking into account the patient's expectation.

IOL exchange: The most common indications for removal or exchange of a modern PCL are wrong IOL power and malposition. Deformation of the implant due to irregular capsular fibrosis may make simple rotation insufficient to properly center the IOL. The IOL may be exchanged for an ACIOL, a sulcus-fixated IOL with or without McCannel sutures, a transsclerally sutured PCIOL, or a posterior iris-claw IOL. [13]

To determine whether the risk-to-benefit ratio favors IOL exchange over observation, the surgeon should consider the following:

Severity, duration, and chronology of the problem Response to nonsurgical treatment

Natural history of a specific IOL

Likelihood that surgical removal would provide substantial relief or benefits

Ease of surgical removal and potential for aggravating or creating additional complications Status of the other eye

Patient and family expectations and visual needs Life expectancy and overall health of the patient

Several indications for surgical intervention exist for a dislocated IOL. If the patient is not satisfied or cannot tolerate aphakic spectacle correction or contact lenses or if there is concomitant retinal pathology, such as a retinal detachment, surgery must be considered.

Several surgical options are available. These options include removal, exchange, or repositioning of the IOL. A multitude of techniques has been described on how to grasp, suture, and place the IOL. Repositioning of the IOL into the ciliary sulcus or over capsular remnants with less than a total of 6 clock hours of inferior capsular support is not a stable situation, as many of those repositioned IOLs will end up dislocating again. Transscleral suturing or IOL exchange (removal of the dislocated IOL and placement of a flexible open loop ACIOL) is recommended in these cases.

In 1996, Kelman proposed a technique called posterior-assisted levitation, in which nuclear fragments or dislocated IOLs into the anterior vitreous are retrieved through a pars plana sclerotomy and the insertion of a cyclodialysis spatula, a needle, or a viscosurgical device. However, this maneuver can be complicated with retinal detachment or cystoid macular edema and should not be performed at all.

If transscleral suturing of the IOL is planned, modifications to the usual placement of the sclerotomies are made. Two triangular scleral flaps are made 180 degrees apart in the horizontal meridian. Then, two sclerotomies are made 1-1. 5 mm posterior to the limbus under the flaps. The infusion cannula is sutured to the usual position. A complete vitrectomy is performed, paying close attention to removing all vitreous and capsular attachments to the IOL, making it freely mobile. The posterior hyaloid, if still attached, is peeled. This allows the IOL to gently fall over the posterior pole of the eye.

If the IOL does not have positioning holes, the edge of the IOL is elevated with a lighted vitreoretinal pick or hook. If positioning holes are present, the IOL may be engaged through them by the pick or hook. The IOL is elevated into the midvitreous cavity, and the optic is grasped with serrated jaw foreign body forceps or diamond-coated forceps. The haptics should not be grasped, or they will be bent.

Aspiration through the silicone soft tipped cannula also has been used in the retrieval and manipulation of the IOL, but this technique may result in inadvertent vitreoretinal traction.

Silicone plate lenses are difficult to manipulate, and, in certain cases, standard techniques will not suffice. The endocryoprobe has been used to engage the IOL, but diamond-coated forceps are much safer. It is recommended that the gas pressure be lowered to 525 psi to avoid freezing the entire shaft. Another problem is that transscleral suturing is not an option because cheese wiring through the silicone will occur.

Liquid perfluorocarbons, such as Perflubron, can be used to float the IOL to the pupillary plane.

Once the IOL is engaged and elevated, it is brought to the posterior chamber. One haptic may be brought in front of the iris. The other haptic may be positioned in the sulcus. Using a Sinskey hook either through a limbal stab incision or through the sclerotomy, the IOL is rotated into place. If more than a total of 6 clock hours of capsular support are present inferiorly, one may elect to reposition the IOL into the sulcus without suturing it.

If there is not enough capsular support, either transscleral sutures or iris sutures are necessary. Several techniques have been described, as follows:

If the IOL has positioning holes, the haptics are rotated until they are in the vertical meridian. Single armed 9-0 Prolene sutures are grasped with intraocular forceps and introduced through the sclerotomies. They are passed through the positioning holes from posterior to anterior. The sutures are tied to the sclerotomies under the scleral flaps.

With the intraocular snare, one of the haptics may be looped, and, at the same time, a 7-0 Prolene suture can be tied to it.

Another option is to temporarily externalize the haptics through the sclerotomies so that they can be tied with 10-0 Prolene sutures. This technique may cause peripheral retina breaks or bleeding. The IOL is repositioned into the sulcus, and the sutures are secured to the sclerotomy.

Needle-guided techniques also have been described where a 9-0 or 10-0 Prolene suture may be threaded retrograde up the bore of a five-eighths-inch 25-gauge needle. The end of the suture that is not threaded is retrieved through the hub of the needle. This results in a suture loop. The needle with the suture is inserted through the base of the scleral flap. As the IOL is being grasped by forceps, the haptic is manipulated into the loop; then, the suture is tied under the scleral flaps.

Under certain situations, an IOL must be exchanged. For instance, if the dislocated IOL is damaged (ie, broken haptic), it must be removed. The damaged IOL may be removed through the pars plana or through a limbal incision at the surgeon's discretion. Pars plana removal increases the risk of retinal detachment and severe choroidal bleeding. Options are as follows:

The surgeon has the choice of suturing a posterior IOL or inserting an ACIOL. Modern flexible open loop ACIOLs do not appear to result in the complications seen with older types (ie, corneal decompensation, uveitis-glaucoma- hyphema syndrome).

Another option is to manipulate the dislocated IOL into the anterior chamber and leave it there. Potential drawbacks of this option are endothelial cell and trabecular meshwork damage. This technique works well with 3-piece polymethyl methacrylate (PMMA) IOLS but requires a peripheral iridectomy to prevent pupillary block.

Perfluorocarbon liquids are very useful if a retinal detachment is also present. The perfluorocarbon liquid bubble displaces the subretinal fluid through the retinal breaks reattaching the retina and, at the same time, serves as a cushion between the IOL and the retina. Thus, the retina is protected from potential damage from IOL impact during surgical manipulation. If a silicone plate lens is dislocated, special care with the use of perfluorocarbon liquids is necessary. It has been reported that these lenses often " skate or glide" on the bubble across the retina. In addition, perfluorocarbon liquids make the grasping of the IOL somewhat more difficult by making the IOL more slippery. If the retina is not detached, the use of perfluorocarbon liquids probably is not necessary.

On certain cases, an ACIOL is present in addition to the dislocated IOL. Surgical management of these cases is made more difficult by the presence of the ACIOL, especially if a concomitant retinal detachment is present. The vitreoretinal surgeon

has several options, as follows:

The surgeon may opt to remove the ACIOL, reposition the dislocated IOL, or suture the dislocated IOL.

Another option is to leave the ACIOL and remove the dislocated IOL. The dislocated IOL may be removed via the pars plana or through a limbal incision. If pars plana removal is entertained, a 7-mm partial-thickness scleral groove is created 3 mm posterior and parallel to the superior limbus. This groove should be contiguous with one of the superior sclerotomies. 8-0 silk sutures should be preplaced through the lips of the scleral groove. Once the IOL is ready to be extracted, the microvitreoretinal (MVR) blade is used to extend the sclerotomy into the scleral groove to make it full thickness. After the IOL is removed, the preplaced sutures are tied. This area is inspected by indirect ophthalmoscopy. If needed, retinopexy is applied.

If extraction through a limbal incision is planned, the ACIOL must be removed first. Then, the dislocated IOL is brought to the anterior chamber and removed through the limbal wound. The ACIOL is reinserted. The limbal wound is closed with 10-0 nylon sutures. The sclerotomies are closed in the usual fashion.

Although dislocated foldable IOLs were traditionally treated with removal of the lens and exchange to a PMMA IOL, one report demonstrates the feasibility of using existing surgical techniques to reposition the dislocated foldable IOLs.

A sutureless technique has recently been described. [14] A 27-gauge needle is passed through the ciliary sulcus, allowing externalization of the IOL haptics. A lamellar scleral dissection is performed, and the haptics are then fixed into this scleral tunnel. Using this technique, the authors report minimal tilt and other complications.

An ab externo scleral fixation of an Akreos AO60 or an ALCON CZ70BD with Gore-Tex suture has been described. [15] Four sclerotomies are made with a microvitreoretinal blade 2 mm from the limbus. CV-8 Gore-Tex suture is passed through the eyelets of the IOL. Each suture end is passed into the anterior chamber through a main incision and externalized through the sclerotomy sites using intraocular forceps in a hand-to-hand technique. The IOL is then placed into the anterior chamber. The sutures are tied, the knots trimmed, and rotated into the sclerotomy.

Consultations

A vitreoretinal specialist should be consulted whenever this complication occurs.

Medication Medication Summary

Pilocarpine hydrochloride sometimes can be used as a trial medication to evaluate symptoms related to edge glare and optical aberrations secondary to IOL decentration.

Miotics

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