Every year, millions of people undergo cataract surgery and receive an intraocular lens (IOL) — an artificial lens implanted to replace the clouded natural lens that has been removed. The procedure has one of the highest success rates in all of surgery, and the vast majority of patients enjoy decades of stable, excellent vision from their implanted lens.
However, the IOL does not remain in place through mechanical anchoring — it relies on a delicate support structure called the zonular fibres. These microscopic fibres, which suspend the IOL within the eye, can weaken and break over time. When enough fibres fail, the IOL shifts out of its intended position — a condition known as IOL dislocation or subluxation. The result can range from subtle blurring to a sudden, dramatic vision change that brings the patient urgently to the ophthalmologist.
How the IOL Stays in Place
After cataract surgery, the IOL is typically placed within the capsular bag — the thin, transparent membrane that originally surrounded the natural crystalline lens. The capsular bag itself is suspended from the internal wall of the eye by approximately 70 radially arranged zonular fibres, like the spokes of a wheel. When these fibres are intact and the capsular bag is healthy, the IOL sits centred and stable in the optical axis of the eye, providing precise focused vision.
In some patients, the zonular fibres are congenitally weak, damaged by disease, or undergo gradual attrition over time. As fibres break — individually or collectively — the IOL tilts, decentres, and eventually may fall entirely out of the capsular bag into the vitreous cavity. This is a late complication of cataract surgery, typically occurring 5–20 or more years after an otherwise uncomplicated original procedure.
"A patient who had perfect vision for fifteen years after cataract surgery and then develops blurring with diplopia should prompt immediate consideration of IOL dislocation. This is a time-dependent complication — it can occur long after the original surgery has been forgotten."
— Dr. Chee Wai WongCauses and Risk Factors
Several conditions predispose to zonular weakness and late IOL dislocation. Understanding the underlying cause influences surgical planning.
Pseudoexfoliation syndrome
The most common identifiable cause. Abnormal fibrillar material accumulates in the eye, progressively weakening the zonules. Highly prevalent in Scandinavian and some Asian populations. Zonular fragility may be present at the time of original cataract surgery or develop in the years following.
High myopia
Highly myopic eyes have longer axial lengths and structurally different zonular attachments. The zonules are under greater mechanical stress and the capsular bag is more prone to fibrosis and contraction, which can erode zonular support over decades.
Trauma
Blunt ocular trauma can rupture zonular fibres acutely, causing immediate subluxation or dislocation. Trauma-related dislocation may occur in younger patients who had cataract surgery for a traumatic cataract.
Connective tissue disorders
Marfan syndrome, homocystinuria, and Ehlers-Danlos syndrome cause zonular weakness as part of their systemic connective tissue pathology. IOL dislocation in these patients may occur at any age after surgery.
Additional risk factors include previous complicated cataract surgery (where the posterior capsule was ruptured or vitreous was lost), uveitis, and retinitis pigmentosa. In a proportion of cases, no identifiable cause is found — so-called idiopathic late IOL dislocation.
Symptoms
The symptoms of IOL dislocation depend on the degree and direction of lens movement. They range from subtle and initially dismissible to dramatic and alarming.
- Blurring of vision — the most common symptom. As the IOL tilts or decentres, its optical power is no longer aligned with the visual axis, causing progressive myopic shift, astigmatism, or simply non-specific blur not correctable by spectacles
- Diplopia (double vision) — when the IOL edge enters the visual axis, patients may see a second image or ghost image alongside the primary one
- Visible edge of the lens — patients may notice a distinct arc or straight line across part of their vision — the edge of the dislocated IOL visible through the pupil
- Fluctuating vision — the IOL may shift with head position, causing vision to change depending on whether the patient is upright, lying down, or bending forward
- Sudden vision loss — in cases of complete dislocation into the vitreous cavity, vision can drop dramatically. A lens in the vitreous exerts traction on surrounding structures and can cause vitreous haemorrhage, uveitis, or retinal damage if left untreated
- Elevated intraocular pressure — a dislocated lens can obstruct aqueous drainage, causing a secondary glaucoma that requires urgent management
Seek prompt review if you experience any of the following after cataract surgery
- Sudden significant change in vision, particularly if years have passed since surgery
- New double vision or ghost image in an eye that has had cataract surgery
- A visible line or arc in your vision suggesting the lens edge is visible
- Vision that fluctuates markedly with head position
5–20 yrs
Typical interval from original cataract surgery to late IOL dislocation
Patients may have forgotten they had cataract surgery when symptoms appear
Surgical Treatment Options
IOL dislocation is a surgical problem requiring a surgical solution. There is no conservative management that will restore a dislocated lens to a stable position. The choice of surgical approach depends on the degree of dislocation, the condition of the capsular bag and remaining zonules, the type of original IOL, and the patient's overall ocular health.
Option 1: IOL Repositioning with Scleral Fixation
If the IOL itself is in good condition, the surgeon may be able to reposition the existing lens and suture it to the scleral wall — bypassing the failed zonular support and providing a new, stable fixation point. This avoids the need to remove and replace the entire lens, which may be technically easier depending on the original IOL design. Sutures are passed through the haptics (the arms of the IOL) and anchored to the sclera, typically using a sutureless or minimally suture-based technique through small scleral pockets.
Option 2: IOL Exchange with Scleral-Fixated Lens
When the existing IOL cannot be repositioned or is not suitable for scleral fixation, the dislocated lens is removed and replaced with a new IOL designed for scleral fixation. Modern scleral-fixated IOLs provide excellent long-term stability without relying on any residual capsular support. The Yamane technique — a sutureless flanged haptic fixation method — has become widely adopted for its reliability and low complication profile. The haptics are threaded through scleral tunnels and flanged externally to anchor the lens permanently.
Option 3: Anterior Chamber IOL
In selected patients, the dislocated IOL is removed and replaced with an anterior chamber IOL — a lens designed to sit in front of the iris, supported by the angle of the anterior chamber. This is a technically simpler approach but is reserved for patients with suitable anterior segment anatomy (adequate corneal endothelial cell count and appropriate chamber depth). Modern angle-supported and iris-claw AC IOLs have acceptable long-term outcomes in appropriate candidates.
What to expect from surgery
IOL repositioning or exchange surgery is performed under local anaesthesia with sedation, typically as a day procedure lasting 1–2 hours. The eye is approached through small scleral ports (vitrectomy technique) to remove prolapsed vitreous and safely manipulate the dislocated IOL. Most patients experience significant improvement in vision within days to weeks of surgery, though a new spectacle prescription will be needed 6–8 weeks post-operatively once the eye has stabilised.
Recovery
Recovery after IOL repositioning or exchange surgery is generally straightforward, and considerably less demanding than retinal detachment repair or macular hole surgery.
Immediate post-operative period
Vision is blurred on day one due to dilating drops and surgical manipulation. An eye pad is worn overnight. Antibiotic and anti-inflammatory drops are started the following morning.
First 1–2 weeks
Vision improves progressively as inflammation settles. Many patients notice a dramatic improvement compared to the dislocated state within the first week. Eye drops are continued for 4–6 weeks.
6–8 weeks
The refractive state of the eye stabilises. A new spectacle prescription is obtained at this point. The power of the new IOL is calculated before surgery, but fine-tuning with spectacles is almost always required post-operatively.
Activity restrictions
Avoid strenuous exercise and heavy lifting for 2–4 weeks. Driving restrictions apply until vision meets legal requirements — your surgeon will advise when it is safe to drive.
Frequently Asked Questions
My cataract surgery was 12 years ago and was completely successful. How can the lens move now?
This is the most common question we encounter from patients with late IOL dislocation — and understandably so. The IOL itself has not changed; what has changed is the supporting structure. Zonular fibres undergo progressive attrition over decades, particularly in the context of pseudoexfoliation syndrome, high myopia, or simply biological ageing of the connective tissue. The capsular bag may also contract and fibrosis over time, eventually eroding the remaining zonular attachment. A successful cataract surgery does not confer lifelong immunity from this mechanical failure.
Can a dislocated IOL be left alone without surgery?
In mild subluxation where vision is only modestly affected, a period of observation with spectacle correction may be reasonable while surgical planning is arranged. However, complete dislocation into the vitreous cavity should not be observed without surgical correction — a loose IOL in the vitreous exerts traction on surrounding structures, can cause uveitis, raised intraocular pressure, and retinal damage over time. The risk of complications increases the longer correction is delayed.
Will my vision go back to what it was before the lens moved?
In most cases, surgical repositioning or exchange restores vision to close to the pre-dislocation level, or better. The new IOL is calculated as carefully as possible to target emmetropia (minimal spectacle dependence), though a spectacle correction for residual refractive error will usually be needed at 6–8 weeks post-operatively. Outcomes are generally excellent in the absence of concurrent retinal or optic nerve pathology.
Is my other eye at risk?
If the dislocation occurred because of pseudoexfoliation syndrome, the fellow eye is at elevated risk of the same complication — pseudoexfoliation is frequently bilateral, though asymmetric. Your ophthalmologist should examine the fellow eye and the stability of any IOL already present there. Patients with systemic conditions such as Marfan syndrome should receive counselling about bilateral zonular risk at the time of cataract surgery in both eyes.
How common is IOL dislocation after cataract surgery?
IOL dislocation is uncommon, occurring in roughly 1–3% of patients who have had cataract surgery, typically years after the original procedure. The risk is higher in patients with pseudoexfoliation syndrome, high myopia, or a history of eye trauma.
How long after cataract surgery can the lens dislocate?
Delayed (late) dislocation is the most common type and can occur anywhere from five to twenty or more years after cataract surgery. It happens as the zonular fibres that hold the lens gradually weaken over time. Early dislocation (within weeks to months of surgery) is less common and usually related to zonular weakness present at the time of surgery.
Is dislocated IOL surgery an emergency?
In most cases, a dislocated IOL is not a medical emergency, but it should be addressed in a timely manner. If the lens has fallen completely into the vitreous cavity causing sudden vision loss, more urgent surgical intervention is advisable. Your eye doctor will assess the degree of dislocation and advise on the appropriate timing for surgery.
What is the success rate of dislocated IOL surgery?
Surgery for dislocated IOL, including vitrectomy with scleral fixation or lens exchange, has a high success rate. Most patients achieve significant improvement in vision compared to their pre-operative state. The final visual outcome depends on the overall health of the eye, particularly the condition of the retina and optic nerve.
Can a dislocated IOL be prevented?
While not always preventable, you can reduce the risk by informing your eye doctor if you have been diagnosed with pseudoexfoliation syndrome, wearing protective eyewear during sports and high-risk activities, and attending regular follow-up appointments after cataract surgery for early detection of any lens position changes.