Intraocular Lens (IOL) Dislocation Clinical Presentation

Updated: May 12, 2021
  • Author: Lihteh Wu, MD; Chief Editor: John D Sheppard, Jr, MD, MMSc  more...
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Presentation

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.

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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.

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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.

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Complications

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

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