AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Background

Cataract surgery is the most common operation performed by ophthalmologists. Although it has a very high success rate, certain complications may occur. Posterior dislocation of an intraocular lens (IOL) is an uncommon complication of cataract surgery and Nd:YAG posterior capsulotomy.

Pathophysiology

Posterior dislocation of an IOL may occur during or shortly after cataract surgery. In these cases, posterior capsular rupture or zonular dialysis usually is present. Rarely, it may occur following Nd:YAG capsulotomy or beyond the immediate postoperative period. Trauma may be a precipitant in these cases.

The IOL rarely dislocates completely onto the retinal surface. It usually lies meshed into the anterior vitreous with one haptic still adherent to the capsule or iris. It may cause a vitreous hemorrhage by mechanical contact with ciliary body vessels. The IOL may be related to retinal detachment or cystoid macular edema secondary to vitreous changes and may cause pupillary block or corneal contact with secondary corneal edema. On many occasions, it does not cause any complications and may be left alone if the patient is able to use aphakic spectacles or contact lenses.

Frequency

United States

It is estimated to occur in 0.2-1.8% of cataract surgery cases.

The frequency appears to have increased in the past few years because of the following reasons: (1) phacoemulsification has a steep learning curve, and, as it becomes more popular, more complications are occurring; (2) anterior segment surgeons are becoming more reluctant to place anterior chamber intraocular lenses (ACIOLs); (3) aggressive placement of posterior chamber IOL in the presence of capsular tears has become more common; and (4) silicone plate IOLs have become popular.

A longitudinal study reported that, in 85% of posterior chamber IOL exchange cases, the indication was decentration/dislocation of the lens.

Race

Race does not play a role in the pathogenesis of this condition.

Sex

No gender preference exists in this condition.

Age

Age is not related to this condition.

CLINICAL

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

History

• Complications during cataract surgery
  
  
  • Posterior capsular rupture
  • Zonular dialysis
• History of Nd:YAG capsulotomy
• History of ocular trauma
• Symptoms
  
  
  • A sudden loss of vision due to uncorrected aphakia, retinal detachment, cystoid macular edema, or vitreous hemorrhage.
  • If the IOL is mobile in the vitreous cavity, the patient may complain of unusual floaters or optical effects.

Physical

• 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

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.
• Postoperative trauma
• 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.

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Gradual or acute loss of vision in patients with intraocular lenses

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

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

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical Care

Observation may be recommended 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

Several indications for surgical intervention exist. 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 have 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.
  
  
  • 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.
  
  
  • 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.
  
  
  • 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, a recent report demonstrates the feasibility of using existing surgical techniques to reposition the dislocated foldable IOLs.

Consultations

A vitreoretinal specialist should be consulted whenever this complication occurs.

FOLLOW-UP

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Further Outpatient Care

• Patients should receive follow-up care as needed.

Deterrence/Prevention

• The anterior segment surgeon should be advised to avoid implantation of a flexible silicone plate IOL if there is a break in the posterior capsule, radial notch, or tear in the anterior capsular rim or zonular dialysis.
• Small capsulorrhexis openings should be avoided.
• Current models of ACIOLs often do not result in the same types of complications as older models. These lenses should be considered if adequate capsular support is lacking rather than risking a posterior dislocation of an IOL.

Complications

• Complications from a dislocated IOL
  
  
  • Vitreous hemorrhage
  • Retinal detachment has been estimated to occur in at least 2% of cases. It frequently is caused by attempts at relocation by the cataract surgeon or as a complication of vitreoretinal surgery.
  • Cystoid macular edema
  • Uncorrected aphakia, glare, or distortion
• Complications from transscleral suture fixation
  
  
  • Late endophthalmitis through the suture track has been reported.
  • IOL torque may occur. In addition, to place the IOL truly in the sulcus, the suture must be placed 0.8 mm posterior to the limbus in the vertical meridian and 0.46 mm in the horizontal meridian. The effective lens power is probably less than the desired one.
  • Vitreous hemorrhage may occur if the major arterial circle of the iris is pierced inadvertently during the maneuvers required to suture the IOL. In addition, these maneuvers also may raise the risk of a postoperative retinal detachment.
  • Erosion of the suture through the conjunctiva also has been reported in cases where scleral flaps were used. An attempt to melt the eroded sutures with the argon laser has been recommended. The sutures cannot be removed because the IOL haptics do not scar into place if placed in the ciliary sulcus. Once the sutures are removed, the IOL will redislocate.

Prognosis

• With proper vitreoretinal techniques, excellent visual results and a low complication rate is possible. Long-term prognosis is highly dependent on the prevention of retinal detachment and choroidal hemorrhage secondary to surgical manipulation.

MISCELLANEOUS

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• The cataract surgeon should avoid any manipulation in the vitreous cavity and allow the vitreoretinal surgeon to manage posterior dislocation.

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

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Article Last Updated: Jul 25, 2007