Dislocated intraocular lens: why it moves years later, and how we fix it in place again

A patient had successful cataract surgery ten years ago, and their vision was excellent. Then they began to notice that their vision was shaking, or that they could see a clear edge at the side of their vision, or that their glasses no longer suited them. After the examination they were told: "The implanted lens has moved out of place." So they ask: "How can a lens that has been fixed for years move? Do I need another operation? Will I lose my sight?" In this article we explain why this happens, and the options for treating it.

How is the lens held in place in the first place?

In cataract surgery, the surgeon removes the contents of the natural lens but leaves its thin, clear outer covering, called the capsular bag or capsule. The artificial lens is placed inside this bag. The bag itself is suspended in place by hundreds of fine fibers, like the guy ropes of a tent, called zonules.

If these zonules weaken over time, the whole bag moves, taking the lens with it. This is called late in-the-bag lens dislocation.

Is it common?

No, but it is not extremely rare either. In an American population study that followed thousands of patients for decades, the cumulative risk was about 0.1% ten years after surgery, rising to about 1.7% after 25 years (Pueringer et al., 2011). In a review of dozens of studies, the rate ranged from 0.5% to 3%, and dislocation occurred on average 6 to 12 years after surgery (Kristianslund et al., 2021).

Who is most at risk?

The conditions most linked to late lens dislocation were (Kristianslund et al., 2021; Pueringer et al., 2011):

• Pseudoexfoliation syndrome, a condition in which a fine material is deposited inside the eye and weakens the zonules.
• Short-sightedness (myopia).
• Previous retinal or vitreous surgery.
• Zonular weakness noticed by the surgeon during the cataract operation itself.

What are the symptoms?

They depend on how far the lens has moved:

• Shaky or changing vision with movement of the eye or head.
• Seeing the edge of the lens or a clear line in the vision, or double vision in one eye.
• A sudden change in glasses prescription.
• If the whole lens has dropped backwards, vision becomes very poor, as if the eye had no lens.

Treatment options: the basic idea

If the lens has moved only slightly and causes no symptoms, monitoring may be enough. If it affects vision, the treatment is surgical. The question that decides the plan is: is there still enough support inside the eye to hold a lens?

Option one: refixating the same lens, or exchanging it

If the lens itself is intact, it can sometimes be refixated with very fine sutures to the wall of the eye, without removing it. In other cases the surgeon prefers to remove it and place a new lens with a different fixation method. In a review of the available studies, the two approaches gave similar vision and similar safety, although the quality of the evidence was generally low (Kristianslund et al., 2021).

Option two: where do we fix the lens when there is no capsule to hold it?

There are several methods, each with advantages and disadvantages:

• An anterior chamber lens (in front of the iris), resting in the angle of the eye.
• An iris-claw lens clipped onto the iris, in front of it or behind it. In an analysis of several studies, the two positions gave similar vision, with a slightly lower chance of macular swelling when it was placed behind the iris (Liang et al., 2021).
• A lens sutured to the iris or to the wall of the eye (sclera) with fine sutures.
• Fixing the lens haptics inside the wall of the eye without sutures (intrascleral haptic fixation). One of the best-known methods fixes the lens haptics in fine tunnels inside the sclera. In a series of 100 eyes with this technique, vision improved and the lens stayed in place; the most common complications were the iris getting caught behind the lens (8%) and minor bleeding inside the eye (5%), with no cases of retinal detachment or infection inside the eye during follow-up (Yamane et al., 2017).

Which method is best?

Every patient asks this, and the honest scientific answer is: no method has been proven better than the others. The American Academy of Ophthalmology has reviewed the available studies twice, about 17 years apart, and both times concluded that the different methods give similar vision, without enough evidence that any one is superior (Wagoner et al., 2003; Shen et al., 2020).

But each method has its own pattern of complications. In the more recent review, macular swelling was more common with some types of sutured lens, chronic raised eye pressure was more common with one type of suture, and retinal detachment was uncommon overall but about twice as frequent with sutured lenses as with methods that do not rely on sutures (Shen et al., 2020).

So the surgeon chooses the method for the eye in question: the state of the cornea, the state of the iris, whether there is glaucoma, the state of the retina, and where the dislocated lens is: still at the front, or dropped backwards and needing a vitrectomy to retrieve it. No single method suits every case.

What can I expect after surgery?

Vision improves in most patients once the lens is stable in the right position, but the final result also depends on the state of the cornea, retina and optic nerve. The American Academy of Ophthalmology stresses the importance of regular long-term follow-up after these operations, because their long-term results are still being studied (Shen et al., 2020).

Complications the doctor watches for include raised eye pressure, macular swelling, bleeding inside the eye, and, in a few cases, retinal detachment (Shen et al., 2020; Yamane et al., 2017).

Questions patients often ask

Is lens dislocation a mistake in the first operation?

Usually not. Most cases happen years later because of weakening of the zonules that hold the bag, a weakness linked to conditions such as pseudoexfoliation, myopia and previous retinal surgery (Kristianslund et al., 2021).

Can the new lens move too?

The aim of the different fixation methods is to hold the lens without relying on the weak zonules. But each method has possible complications, including, rarely, the lens moving again, which is why follow-up continues (Shen et al., 2020).

Will I need retinal surgery too?

If the lens has dropped backwards inside the eye, the surgeon usually needs to remove the vitreous to retrieve it safely, and then fix the lens. If it is still at the front, this may not be necessary.

Can glasses help instead of surgery?

If the lens has moved only slightly and the symptoms are not troublesome, monitoring and adjusting the glasses may be enough. But if the lens is clearly dislocated, glasses do not solve the problem.

Summary

Dislocation of the implanted lens years after cataract surgery is uncommon but well recognized, and is usually linked to weakening of the zonules that hold the lens bag. When it affects vision, treatment is usually surgical, by refixating or exchanging the lens, and there are several fixation methods, none proven better than the others. So the choice is based on each eye, with long-term follow-up after surgery. We make sure each patient understands why we chose the method that suits their case, and what its expected risks are.

This information is for health education and does not replace a medical examination.