Sudden vision loss, pain, redness, flashes or a “curtain”
Seek urgent ophthalmic care. Social media and FAQ pages are not appropriate for emergency consultation.
What has happened
Causes, symptoms and warning signs
What intraocular lens dislocation is, why it may occur years after surgery and which symptoms should not be ignored.
What is an artificial lens, and what exactly becomes displaced?+
During cataract surgery, the surgeon removes the cloudy contents of the natural lens while preserving its thin outer membrane — the capsular bag. The intraocular lens is implanted inside it.
The capsular bag is held in the eye by a system of fine zonular fibres. If this support weakens, the lens may lose its stable central position. The IOL material itself is usually not “damaged”; the problem is loss of support.
How the degree of displacement is described
- Decentration — the optic is slightly displaced from the centre of the pupil.
- Subluxation — part of the support is lost, and the lens is visibly tilted or mobile.
- Complete dislocation — normal support is substantially lost; the IOL may move forwards or backwards.
Key point
For treatment decisions, the stability of the lens, quality of vision and effects on surrounding ocular structures are more important than the label assigned to the degree of displacement.
When can displacement occur, and why does it happen?+
Early displacement may be related to inadequate capsular or zonular support after surgery. Late dislocation can develop after a long period of stable vision. Reviews have reported an average interval of 6–12 years after cataract surgery, although the timing can vary considerably between patients.
Known risk factors
- pseudoexfoliation syndrome;
- high myopia and increased axial length;
- eye trauma;
- previous vitreoretinal surgery;
- uveitis or another chronic intraocular inflammatory condition;
- marked capsular bag contraction;
- zonular weakness identified during the original surgery.
Sometimes no single obvious factor is found; a combination of age, ocular characteristics and progressive changes in the capsular bag may be relevant.
Key point
Patients generally cannot identify pseudoexfoliation syndrome themselves; it is detected by an ophthalmologist during examination.
What symptoms may a patient notice?+
- gradual or sudden reduction in vision;
- a sensation that the image is shaking or “floating”;
- double vision that persists when the other eye is closed;
- a semicircular shadow, arc or lens edge in the field of vision;
- new glare and halos, especially with a dilated pupil in the dark;
- inconsistent benefit from glasses;
- changes in visual quality when tilting the head or moving the eye.
Mild decentration may cause no symptoms and be found incidentally. Conversely, even a relatively small displacement of certain IOL designs can noticeably impair image quality.
Key point
The degree of displacement cannot be determined from symptoms alone: similar complaints may occur with corneal, retinal or optic nerve disease, or with a refractive change.
Why do double vision, glare and awareness of the lens edge occur?+
If the IOL optic no longer aligns with the centre of the pupil, light rays pass through different optical zones. The patient may therefore see a double contour, a bright arc, a semicircular shadow or an area of the image with different quality.
Double vision that persists when the other eye is closed is called monocular diplopia. Double vision occurring only with both eyes open may have another cause and therefore requires separate assessment.
If the “IOL–capsular bag” complex is unstable, the image may change with eye movement, after sleep or when head position changes.
Key point
A description of the symptom is helpful, but it does not replace examination with both an undilated and a dilated pupil.
Can displacement cause pain, and why can it be dangerous?+
Marked or progressive dislocation may be accompanied by inflammation, impaired aqueous outflow, increased intraocular pressure, or damage to the iris or cornea.
Possible consequences include substantial visual loss, secondary glaucoma, corneal oedema, chronic inflammation and the need for more complex surgery. The visual prognosis depends not only on IOL position but also on the condition of the retina and optic nerve.
Key point
Severe pain is not a typical feature of a small, stable displacement and requires more urgent assessment.
When should urgent care be sought, and what should be done before examination?+
Urgent examination is required for
- sudden or rapidly worsening vision;
- severe or increasing pain;
- marked redness or photophobia;
- nausea or vomiting occurring with eye pain;
- flashes or many new floaters;
- a dark “curtain” or “veil” in the field of vision;
- eye trauma;
- sudden deterioration after a period of improvement.
Before examination
- do not press on the eye or try to “put the lens back” yourself;
- avoid trauma and substantial physical exertion;
- do not start new eye drops without medical advice;
- bring your discharge summary and information about the IOL model, if available;
- do not drive yourself if vision has suddenly worsened.
Key point
Even if visual instability temporarily resolves, the position of a mobile IOL may continue to change; examination is still necessary.
Examination and treatment planning
How the ophthalmologist assesses IOL position, when observation may be appropriate and what determines the urgency of surgery.
How the decision is made
Examination and treatment planning
Which tests help assess IOL position, when observation may be appropriate, and why treatment cannot be selected from a photograph alone.
How does the ophthalmologist determine the position of the artificial lens?+
The basic examination usually includes
- measurement of uncorrected and corrected visual acuity;
- refraction;
- measurement of intraocular pressure;
- slit-lamp biomicroscopy;
- assessment of IOL position with an undilated and a dilated pupil;
- fundus examination.
The ophthalmologist assesses not only the degree of displacement but also IOL mobility and the condition of the capsular bag, iris and cornea.
Key point
The scope of examination varies according to fundus visibility, coexisting glaucoma, retinal disease and the anticipated surgical approach.
Why is the pupil dilated, and when are ultrasound, OCT or UBM needed?+
Pupil dilation helps assess IOL centration and stability, the capsule, peripheral retina and vitreous.
B-scan ultrasonography is used when the fundus cannot be seen clearly or the lens has moved posteriorly.
Ultrasound biomicroscopy may help define the position of the IOL and its supporting elements in the anterior segment.
OCT helps assess the macula and optic nerve; this is important when the expected visual outcome may be limited by conditions other than IOL displacement.
Key point
Not every patient requires every test. The ophthalmologist determines the appropriate investigations after the initial examination.
Does every displaced IOL require surgery?+
Observation may be considered if
- the patient is satisfied with their vision;
- the lens position remains stable;
- there is no significant double vision or optical discomfort;
- intraocular pressure is controlled;
- there is no inflammation or damage to the cornea or iris;
- the patient is willing to attend regular follow-up examinations.
Observation does not mean the problem can be forgotten. The ophthalmologist monitors changes in IOL position and the condition of the eye.
Key point
The decision is based not on a single measurement but on the combination of symptoms, anatomy and risks.
What determines the urgency of surgery?+
More prompt intervention may be required for sudden visual deterioration, IOL contact with the cornea, marked inflammation, uncontrolled pressure elevation, tissue entrapment, or displacement of the lens into the anterior chamber or vitreous cavity.
When the position is stable, vision is satisfactory and complications are absent, surgery may sometimes be scheduled after complete examination and preparation.
Key point
The term “elective surgery” does not mean that follow-up can be postponed indefinitely.
Why can treatment not be selected from a photograph?+
Two situations that look similar externally may require different operations. Treatment planning requires knowledge of the IOL model, integrity of its supporting elements, and the condition of the capsular bag, iris, cornea and posterior segment.
IOL position may change with eye movement and is often better assessed directly during examination. In some cases, whether the lens can ultimately be retained becomes clear only during surgery.
Key point
Remote review of a photograph may help determine the need for an in-person examination, but it should not be used to select a specific operation.
What determines the visual prognosis after treatment?+
If optical displacement of the IOL is the main cause of reduced vision, stabilising or replacing it may improve visual function. However, surgery cannot reverse irreversible retinal, optic nerve or corneal damage.
The prognosis is also affected by glaucoma, age-related macular degeneration, diabetic retinal changes, previous inflammation and trauma.
Key point
A specific postoperative visual acuity cannot be promised before examination. The ophthalmologist discusses the expected range of outcomes and limitations individually.
Surgical treatment
IOL repositioning or exchange, fixation options, anaesthesia and preparation for surgery.
When an intervention is required
Surgical treatment
How IOL repositioning differs from exchange, which fixation options are available and why the final approach must always be individualised.
When does surgical treatment become necessary?+
The aim of surgery is to restore a stable central position of the optical system and address complications caused by a mobile or malpositioned IOL.
Indications are determined with consideration of the patient’s symptoms, everyday visual demands, ocular condition and risk of further displacement.
Key point
Surgery for IOL dislocation aims to improve image quality and protect the eye, but it cannot guarantee recovery of vision lost because of other diseases.
How does IOL repositioning differ from IOL exchange?+
Repositioning
It may be considered if the lens design is suitable, the IOL is undamaged, its optical properties are satisfactory and it can be stabilised safely.
Exchange
It may be required if the existing IOL cannot be secured reliably, is damaged, is unsuitable for the selected fixation method or must be removed for another reason.
Studies indicate that both strategies can provide satisfactory visual outcomes. The choice depends on the individual anatomical situation.
Key point
There is no single method that is best for every patient.
How can the lens be fixed inside the eye?+
Scleral fixation secures the supporting elements of the IOL to the sclera. Both sutured and sutureless techniques are available.
Iris fixation is used in selected situations and with suitable lens designs.
Sometimes part of the capsular support can be retained; in other cases, a secondary IOL designed for an alternative fixation method is required.
Key point
The name of a technique alone does not allow its “quality” to be compared. The surgeon’s experience, tissue condition and suitability of the method for the individual eye are what matter.
When is vitrectomy needed, and how is a new IOL selected?+
Removing part of the vitreous allows the displaced IOL to be freed and stabilised safely, reduces traction and provides access to a lens located in the posterior segment.
Selection of a new IOL takes into account the condition of the capsular bag, iris and cornea, axial length, optical power calculation and the planned fixation method.
Key point
The need for vitrectomy does not mean that every patient requires the same extent of surgery.
What type of anaesthesia is used, is the operation painful, and is hospital admission required?+
During surgery, the patient may usually notice touch, fluid, light and movement, but should not experience severe pain. Any discomfort should be reported to the surgical team immediately.
The duration can only be estimated in advance because it depends on IOL position, the condition of the capsule and vitreous, the need for vitrectomy and the fixation method.
Surgery may be performed as a short-stay procedure or with hospital admission, according to the arrangements of the treating institution.
Key point
Preoperative fasting instructions depend on the type of anaesthesia. Follow the instructions provided by your clinic.
Should blood-thinning medicines be stopped, and which risks are discussed?+
Tell the doctor the medicine name and dose, why it was prescribed, and whether you have coronary stents, prosthetic valves, atrial fibrillation, or a history of thrombosis, stroke or myocardial infarction.
Possible surgical risks
- inflammation and infectious complications;
- an increase or decrease in intraocular pressure;
- haemorrhage;
- corneal or macular oedema;
- retinal tear or detachment;
- change in pupil shape;
- residual displacement or recurrent dislocation;
- the need for an additional procedure.
The individual risk profile depends on the preoperative condition of the eye and the selected technique.
Key point
If a medicine is temporarily withheld, the patient should receive precise written instructions specifying the last dose and when treatment should be restarted.
Recovery and follow-up
Eye drops, restrictions, return to usual activities and symptoms that should not be ignored.
After surgery
Recovery and follow-up
What sensations may occur during the first few days, how to use eye drops, when to return to normal activities and which symptoms require urgent examination.
Why does vision not recover immediately after surgery?+
The rate of recovery depends on the extent of surgery and the preoperative condition of the cornea, retina and optic nerve. Vision may stabilise more slowly after a complex procedure than after standard cataract surgery.
During the first few days, the following may occur
- moderate blurring;
- a foreign-body or gritty sensation;
- tearing and mild photophobia;
- mild redness;
- fluctuation in visual quality.
Key point
Symptoms should gradually improve. Increasing pain, redness or visual deterioration should not be regarded as part of normal recovery.
How should postoperative eye drops be used?+
- Wash your hands.
- Tilt your head back and gently pull down the lower eyelid.
- Instil one drop into the pocket without touching the eye with the bottle.
- Close the eye without squeezing it tightly.
- If several medicines have been prescribed, keep the interval specified by your doctor; eye drops are generally not instilled simultaneously.
If you miss a dose, do not double the next one unless instructed by your doctor. The regimen may be adjusted at follow-up visits.
Key point
Do not stop anti-inflammatory or pressure-lowering drops on your own, even if the eye appears quiet.
How should I sleep, wash, bend down and lift weights?+
During early recovery, patients are generally advised not to rub the eye and to avoid direct exposure to unclean water or cosmetics, trauma, sudden exertion and activities requiring forceful straining.
Advice about sleeping on the operated side, bending, lifting weights and washing the hair depends on the surgical technique, retinal condition and any additional procedures performed.
Key point
If the website guidance differs from your surgeon’s written instructions, the individual written instructions take priority.
When can I use a computer, exercise and drive?+
Brief visual activity does not usually damage the IOL, but it may cause fatigue and dryness during the first few days. Take breaks and do not continue through pain or marked discomfort.
Intensive exercise, contact sports, swimming pools, saunas and heavy physical work should be resumed only after approval from the surgeon.
Driving may be resumed when vision meets safety requirements, double vision is absent and the doctor has not imposed additional restrictions.
Key point
Do not drive on the day of surgery or while vision is unstable, double or blurred.
Will new glasses be needed, and why can refraction change?+
A change in IOL position affects focusing. When the lens is exchanged, the result depends on the power calculation, the available fixation site and the individual characteristics of the eye.
Temporary glasses may be helpful during recovery, but final prescription too early may be inaccurate.
Key point
The ophthalmologist determines when spectacle correction should be assessed based on the progress of the individual eye.
How often are follow-up visits needed, can the IOL dislocate again, and when is urgent care required?+
The follow-up schedule depends on the surgical technique and early postoperative course. Do not miss visits even if the eye feels well.
Seek urgent care for
- sudden or worsening loss of vision;
- severe pain;
- rapidly increasing redness;
- purulent discharge;
- flashes, many new floaters or a “curtain”;
- trauma to the operated eye;
- deterioration after initial improvement.
Final vision depends on successful IOL stabilisation and the condition of the other ocular structures.
Key point
If warning symptoms occur, do not wait for the scheduled follow-up date and do not rely solely on a message through social media.
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Sources
- Russian Ministry of Health. Clinical guidelines “Age-related cataract”, 2024. Effective January 1, 2025.
- Miller K.M. et al. Cataract in the Adult Eye Preferred Practice Pattern®. Ophthalmology. 2022;129(1):P1–P126. doi:10.1016/j.ophtha.2021.10.006.
- Kristianslund O., Dalby M., Drolsum L. Late in-the-bag intraocular lens dislocation. J Cataract Refract Surg. 2021;47(7):942–954. doi:10.1097/j.jcrs.0000000000000605.
- Khoramnia R., Baur I.D., Auffarth G.U. Aetiology and Management of IOL Dislocations. Klin Monbl Augenheilkd. 2023;240(8):971–980. doi:10.1055/a-2074-9028.
- Armonaite L., Behndig A. Repositioning of in-the-bag Dislocated Intraocular Lenses: A Randomized Clinical Trial Comparing Two Surgical Methods. Ophthalmic Res. 2023;66(1):590–598. doi:10.1159/000529506.
- Nakagawa S. et al. Background factors determining the time to intraocular lens dislocation. Int Ophthalmol. 2024;44:240. doi:10.1007/s10792-024-03166-x.
- Zhang C. et al. Clinical Outcomes in Scleral Fixation Secondary Intraocular Lens with Yamane versus Suture Techniques: A Systematic Review and Meta-Analysis. J Clin Med. 2024;13(11):3071. doi:10.3390/jcm13113071.
- Sun H., Wang C., Wu H. Recent advances and current challenges in suture and sutureless scleral fixation techniques for intraocular lens: a comprehensive review. Eye Vis (Lond). 2024;11:49. doi:10.1186/s40662-024-00414-0. Correction published in 2025.
- Tripathi M., Rao S., Sinha R. Scleral-fixated IOLs — a comprehensive review of current practices and emerging trends. Indian J Ophthalmol. 2025;73(7):933–945. doi:10.4103/IJO.IJO_2812_24.
- Kristianslund O. et al. Late In-the-Bag Intraocular Lens Dislocation: A Randomized Clinical Trial Comparing Lens Repositioning and Lens Exchange. Ophthalmology. 2017;124(2):151–159. doi:10.1016/j.ophtha.2016.10.024.
This material is for information and education only. It does not establish a diagnosis, is not intended for self-prescribing or stopping treatment, and does not replace an in-person consultation with an ophthalmologist. Your individual discharge instructions and the recommendations of your treating doctor take priority.