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Evaluation, management of dislocated IOLs for positive outcomes
Understanding the cause of a dislocated IOL is imperative to formulating a treatment plan.
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When implanting a lens at the time of cataract surgery, achieving the best visual performance requires that it is well-centered. A dislocated IOL can cause many patient symptoms, such as diplopia, ghosting, glare and distortion.
At times, patients with severely decentered IOLs can have seemingly normal Snellen test readings because the test does not measure contrast sensitivity or visual quality. If an IOL becomes decentered, it is important to understand the reason behind why it has become dislocated and then formulate a plan for treatment.
Capsular details
Because the default position for the IOL during routine cataract surgery is fully within the capsular bag, the capsular bag must be carefully examined to judge the integrity of the capsulorrhexis, the posterior capsule and the zonular support. Using a retro-illumination lighting technique is helpful in detecting capsular details during slit lamp examination.
If the IOL is not fully within the capsular bag, it may become decentered, tilted or dislodged. A common scenario is for the leading haptic and optic to go into the capsular bag during IOL insertion, but the trailing haptic is inadvertently placed above the anterior capsular rim in the ciliary sulcus (Figure 1a and 1b). This is more likely to happen when there is a degree of pupillary miosis during cataract surgery and the placement of the trailing haptic is not directly visualized.
The size and morphology of the capsulorrhexis is important for fixation and centration of the IOL within the capsular bag. If the capsulorrhexis is oversized, irregular or radialized, it may not securely hold the IOL in position as the eye heals from surgery. Future capsule contraction or fibrosis can cause the IOL to become even further dislodged and induce more visual symptoms.
Lens placement
When there is a break in the posterior capsule, three-piece IOLs can be placed in the ciliary sulcus as long as there is sufficient anterior capsular support. Care must be taken to avoid vitreous prolapse into the anterior chamber because it can displace the IOL optic from the visual axis and place traction on the retina, which can lead to further complications such as retinal detachment or macular edema.
Figure 1. All of these IOLs have become decentered due to issues with capsular support. A single-piece acrylic IOL (A) was partially inserted into the capsular bag but because the trailing haptic was inadvertently placed into the sulcus, the IOL became decentered. This can happen to three-piece IOLs as well (B). In some cases, an irregular or radialized capsular opening provides insufficient support for the IOL, which may become subluxated (C) or superiorly displaced (D).
Images: Devgan U
Figure 2. Traumatic injury to this eye (A) has resulted in zonular damage and dislocation of the plate haptic IOL, which is still fully within the capsular bag. In some cases when IOLs have been primarily implanted into the ciliary sulcus, trauma (B), gradual drift (C) and too small of an IOL (D) can cause the IOL to become decentered.
Figure 3. Phimosis of the anterior capsule can cause a slight decentration of the IOL (A) or can lead to severe dislocation with loss of zonular support (B). Vitreous strands (C, green arrow) can cause peaking of the pupil margin (C, yellow arrow) and displacement of the IOL. Placement of a single-piece acrylic IOL in the sulcus (D) has resulted in sunset syndrome of the optic and chaffing of the posterior surface of the iris, causing chronic inflammation and iris transillumination defects.
Sulcus-based IOLs should be larger in overall length because the diameter of the ciliary sulcus is larger than the capsular bag diameter. An IOL that is too small has a tendency to slip inferiorly and out of position, often referred to as sunset syndrome. Of particular importance is to avoid placing a single-piece acrylic IOL in the ciliary sulcus because, in addition to being too small, its thick haptics can cause chronic inflammation and damage from chaffing of the posterior iris surface.
In other cases, the entire capsular bag and IOL complex can become dislocated, such as in trauma, diseases with progressive zonulopathy and severe anterior capsular phimosis.
Treatment
The treatment of a dislocated IOL varies based on the clinical scenario and status of the capsular support. In some cases, treatment may include repositioning of the existing IOL with or without suture fixation, but in others, it may require explanting the existing IOL and replacing it with a more suitable design for iris suturing, intrascleral glued fixation or anterior chamber placement.
Risks associated with further surgery are greater than for the original cataract surgery, and patients should have reasonable expectations. In most cases, we can successfully address dislocated IOLs and improve vision for our patients.