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Correcting vision in an eye that already has a lens implant
It is a common situation, and one that is rarely explained. The operation made the eye clear again, but did not free you from glasses: you need them to read, sometimes to drive. Many patients assume the matter is closed. It is not: there are three solutions, and choosing between them is far from obvious.
Understanding
There are five possible explanations, and they do not call for the same answer. The first step is to find out which one applies to you: that is what the consultation is for.
This is the case in the vast majority of operations, and it is the only implant covered by French national health insurance (Assurance Maladie). It gives sharp vision at a single distance, usually for distance: reading glasses are still needed. This is not a flaw in the operation; it is what was agreed at the outset.
The formulas used to calculate the implant have their limits, and some eyes do not fit them well: high myopia, corneas previously treated by laser, short eyes. A prescription of a few dioptres then remains, known as a refractive surprise.
If the implant fitted was not toric, the corneal astigmatism you already had remains. It blurs vision at all distances, and it can still be corrected now.
Clouding of the capsule that holds the implant (posterior capsule opacification) can on its own explain hazy vision, sometimes years later. It is treated with a YAG laser, during a consultation, in a few minutes. This is the first thing to check: there is no point considering anything else until it has been ruled out. Find out more →
Macular disease, glaucoma or diabetic retinopathy limit vision regardless of the implant. No refractive surgery will correct them, and their presence generally rules out multifocal lenses.
The assessment beforehand
Any one of these tests can, on its own, rule out surgery. That is also why no answer can be given over the phone.
The options
None is better than the others: they answer different situations, and the assessment points to the one that suits you.
PRK or LASIK treats the residual prescription without entering the eye. It is the simplest option when the error is small and the cornea allows it.
For: nothing done inside the eye, high precision on small corrections.
Against: limited by corneal thickness, does not correct presbyopia, permanent.
A second, thin implant is slipped in front of the one already in place. It corrects the residual error and, in its multifocal version, can add near vision.
For: reversible, the first implant is left untouched, corrects larger errors and can add presbyopia correction.
Against: a procedure inside the eye, needs enough anatomical space, risks specific to its position.
The implant in place is removed and replaced. This is the solution for implants that are poorly positioned, badly miscalculated or poorly tolerated.
For: deals with the root cause, only one implant in the eye at the end.
Against: the most delicate of the three. Over the years the implant adheres to the capsule, and removing it carries a risk of complications.
It is an option, and sometimes the right one. Well-fitted reading glasses give excellent near vision, with no halos, no risk and no cost.
The question is not ‘can it be done?’ but ‘is the inconvenience enough to justify another procedure inside the eye?’. It deserves a frank discussion at the consultation.
The add-on lens
The idea is to add rather than replace. That is what makes it simpler than an implant exchange, and reversible.
The add-on lens is a thin lens placed in the sulcus: the space behind the iris and in front of the implant already in place. It does not replace that implant: the two sit together, the first one staying in the capsular bag where it was placed during your operation.
This position explains both its benefits and its constraints. There is no need to reach the existing implant, which makes the procedure much simpler. But there has to be enough room, and a model designed for this exact location.
Corrects residual myopia or hyperopia: a prescription left over after the first implant was fitted.
Corrects astigmatism, when the original implant was not toric and the blur persists at all distances.
Adds near vision to an eye corrected for distance. This is the version most patients are interested in: it turns a monofocal eye, at a later stage, into one that manages without glasses.
A multifocal implant placed in the capsular bag at the first operation is very difficult to remove if it is not tolerated: over time, it adheres to the capsule. An add-on can be removed: it has never adhered to anything.
So multifocal vision can be tried while keeping a way out. That changes a great deal in how the decision to operate is made, and means it can be offered to patients who would not otherwise have been operated on.
The safety of this surgery depends closely on the design of the implant. Only models specifically designed for the sulcus are suitable.
A standard implant, not intended for this position, rubs against the back of the iris: it releases pigment, keeps inflammation going and raises the pressure. It is the most avoidable complication of this technique, and it depends entirely on the surgeon's choice.
The available studies involve small numbers and short follow-up: a few dozen eyes, followed for three months to a year. They report good distance, intermediate and near vision, comparable to a multifocal implant fitted at the first operation, with no major complication attributed to the add-on.
That is encouraging, but it is not the level of proof that established techniques have. I will put it to you plainly: this is an interesting option, not a solution tested on thousands of patients.
Risks
This surgery is not necessary: it is done for comfort. So the duty to inform you is all the greater, and the level of risk that is acceptable all the lower.
The implant can rub against the back of the iris, releasing pigment. This leads to inflammation, raised intraocular pressure and sometimes bleeding, a combination known as uveitis-glaucoma-hyphaema syndrome. The risk depends closely on the model fitted: it is low with implants designed for this position.
Reported frequency, depending on the study and the model. It is caused by inflammation, released pigment or steroid treatment, and is usually treated with medication.
Fluid builds up in the central area of the retina and reduces vision. It already occurs in 1 to 3% of uncomplicated cataract operations. An OCT scan is done at the slightest suspicion.
Frequency reported at three months with multifocal implants, with very variable intensity. Glare and starbursts around lights can come on top. These are not complications but optical properties, and they have to be accepted before the operation.
A poorly centred implant lowers the quality of vision and makes halos worse. A rotation cancels the effect of a toric correction. The implant may need repositioning.
As with any surgery that opens the eye. Rare but serious, and prevented by strict antisepsis and preventive antibiotics.
You can see today, and you see well with your glasses. Any further operation puts at risk an eye that works. If the inconvenience is moderate, doing nothing is often the best decision, and I will tell you if that is my view.
SFO information leaflets (in French)
These leaflets are published by the Société Française d'Ophtalmologie (French Society of Ophthalmology). They describe the procedure, its results and its risks. They serve as the basis for informed consent and do not replace the consultation.
The procedure
It takes place in the operating theatre at Clinique Les Martinets, in Rueil-Malmaison, across the road from the practice. As a day case, under local anaesthesia with anaesthetic eye drops, like cataract surgery itself.
The refraction must be stable, and the capsule treated if it has clouded. Biometry, topography, macular OCT, endothelial cell count and assessment of the space available behind the iris.
The report from your first operation and the model of the implant fitted are very useful: please bring them.
Admission at Clinique Les Martinets, 97 avenue Albert 1er. Anaesthetic eye drops, an eyelid speculum to hold the eye open, then an incision of about three millimetres at the edge of the cornea. A protective gel holds the space open; the second implant goes in folded, through an injector, and is then slipped behind the iris, in front of the implant already in place.
The gel is then fully removed by suction, an antibiotic is injected and the centring of both implants is checked. About fifteen minutes. You go home the same day.
I check the intraocular pressure, the inflammation, the position of the implant and that the incision is sealed. This is brought forward to 24 hours if it is your only functioning eye.
Antibiotic and anti-inflammatory eye drops, a protective shield at night.
The final refraction is measured at these two visits: only then can the result be judged and any supplementary glasses prescribed.
With a multifocal implant, neuroadaptation then continues over several weeks to several months.
The five stages of fitting: front view, then cross-section of the front of the eye
Anaesthetic eye drops. The eye has already been operated on: an implant sits in its capsular bag, and it will not be touched.
An incision of about 3 mm at the edge of the cornea, then a protective gel that holds the space open and protects the tissues.
The second implant, soft and folded, is passed through the micro-incision with an injector, then unfolds by itself.
The add-on is slipped behind the iris, in front of the implant already in place, into the space between them. The two implants lie one in front of the other without touching.
The gel is fully removed by suction, an antibiotic is injected and the centring of both implants is checked. The micro-incision closes by itself, without stitches.
Area concerned Add-on lens Iris Implant in place Protective gel
In practice
Frequently asked questions
Most often because the implant fitted was monofocal: it gives sharp vision at a single distance, usually for distance. There may also be some uncorrected astigmatism, or a small residual error linked to the implant calculation.
Yes. There are three routes: a laser enhancement on the cornea, adding a second implant in front of the first, or replacing the implant. The choice depends on the remaining prescription, the condition of your eye and what you are hoping for.
A second, thin implant, slipped in front of the one already in place, in the space behind the iris. It is added without touching the first, and can be removed if it is not tolerated: that is its main advantage.
That is its defining feature: it can be removed, which is not the case for a multifocal implant placed in the capsular bag at the original operation. Removing it does, however, mean another operation inside the eye.
Yes, as with any multifocal implant. Studies report halos in about 45% of patients at three months, with very variable intensity. They fade with neuroadaptation, but have to be accepted before you decide.
It is possible, but more delicate: after some years the implant adheres to the capsule, and removing it carries a risk of complications. The add-on avoids having to reach it. Replacement is still preferable in some situations, particularly when the implant is poorly positioned.
Yes. The refraction must have settled, and any secondary cataract must be treated first, because clouding of the capsule can on its own explain blurred vision. Nothing is decided until the situation is stable.
A full refraction, biometry, an examination of the cornea and tear film, an OCT scan of the macula, a check of the optic nerve and eye pressure, an endothelial cell count and an assessment of the space available behind the iris. Any one of these can on its own rule out surgery.
Bring the report from your operation, the model of the implant fitted if you know it, and your past glasses prescriptions. These documents save a whole consultation.
Dr Emmanuel Halimi
Ophthalmic surgeon · RPPS 10100555084 · Medical Council of Hauts-de-Seine no. 92/23003
Page written and approved by the surgeon.
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