Home / Refractive surgery / ICL phakic lens
ICL, a lens inside the eye that leaves the cornea untouched
When the prescription is too high or the cornea too thin, laser reaches its limits: it would have to remove more tissue than the cornea can spare. The phakic lens gets round the problem by slipping a soft lens between the iris and the natural lens, which stays in place. The cornea is not altered, and the implant can be removed.
The principle
The whole logic of the phakic lens lies in this reversal. Laser corrects by removing tissue; the implant corrects by adding material.
The word phakic comes from the Greek phakos, the lens of the eye. It means that the natural lens is kept: this is what sets this implant apart from the one placed during cataract surgery or a PreLex procedure, where the natural lens is removed.
The most widely used implant is the ICL (Implantable Collamer Lens). It is a thin, soft lens made of a biocompatible material, placed in the posterior chamber: behind the iris, in front of the natural lens. It stays stable there, invisible, and you cannot feel it.
Its power is calculated for your eye, and its size chosen from precise biometric measurements. It corrects myopia, hyperopia and, in its toric version, astigmatism, including at levels well beyond the reach of corneal laser surgery.
Every dioptre corrected by laser uses up corneal thickness. Beyond a certain threshold, there would not be enough tissue left for the cornea to stay strong, and the risk of ectasia (progressive, irreversible deformation) would become unacceptable. The pachymetry measured at the assessment sets this limit for each eye. The phakic lens uses up nothing.
Why the implant, and where it sits
Cornea too thin, prescription too high, irregular topography, suspected keratoconus, severe dry eye.
A soft lens is slipped between the iris and the natural lens, which stays in place. The cornea is not touched, so its thickness no longer matters. And the implant can be removed.
Phakic lens Natural lens kept Iris
Step by step
The procedure is short and recovery is quick. What comes before it, the anatomical measurements, is on the other hand particularly demanding.
It checks that the implant can be placed safely and will be well tolerated over time. Three measurements are decisive: the anterior chamber depth, how open the iridocorneal angle is (gonioscopy) and the endothelial cell density.
Added to these are topography, pachymetry, refraction under cycloplegia and a dilated eye examination (fundus examination), all the more important because high myopia carries a risk of peripheral retinal lesions.
As a day case, usually under local anaesthesia with anaesthetic eye drops. General anaesthesia is still possible: the arrangements are discussed with the surgeon and the anaesthetist at the preliminary consultations.
A micro-incision of about three millimetres is made at the edge of the cornea, and a protective gel holds the space open during the procedure. The implant, folded inside an injector, is introduced, then unfolds and is slipped behind the iris, its four footplates tucked in at the periphery. The gel is then removed and an antibiotic injected. The incision seals on its own.
Under general anaesthesia, you are aware of nothing. Under local anaesthesia, you lie down with your head supported to prevent any movement, and you feel no pain.
You do not see the instruments: what you mostly notice is the glare of the operating microscope lights. A protective shield is put in place at the end, to be worn every night for a week.
Mild discomfort, stinging and blurred vision are normal in the first few hours, as is a temporary narrowing of the pupil. Vision becomes functional within 24 to 72 hours, one of the fastest recoveries in refractive surgery, since the cornea is not reshaped. Fluctuating refraction, dryness and halos are common in the first few days, and the refraction settles within two to six weeks.
Eye drops to be put in regularly, the shield at night, no rubbing your eyes, no make-up and no water in the eyes for two weeks. The two eyes are operated on one week apart.
The five stages of implantation: front view, then cross-section of the anterior segment
Anaesthetic eye drops. The natural lens is kept: this is what sets the phakic lens apart from cataract surgery.
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 soft, folded implant is introduced through the micro-incision with an injector, then unfolds by itself.
The implant is slipped behind the iris, in front of the natural lens, its four footplates tucked in at the periphery. It cannot be seen from the outside.
The gel is completely removed, an antibiotic is injected into the eye, and the position of the implant is checked. The micro-incision seals on its own, without stitches.
Area involved Implant Iris Natural lens kept Protective gel
The choice
This is not a ranking but a division of roles. Laser remains the first option when it is possible; the implant takes over when it is not, or when laser would put the cornea at risk.
| Its strengths | Its limits |
|---|---|
| A much wider range of correction: it treats myopia, hyperopia and astigmatism that laser cannot reach for lack of corneal thickness. | A procedure inside the eye: the eye is opened, which carries a risk of endophthalmitis, low but inherent in this type of surgery. Corneal laser surgery does not carry this risk. |
| An intact cornea: no flap and no removal of stroma, so no risk of induced ectasia or biomechanical weakening. | A risk of early cataract: rare, linked to how close the implant sits to the natural lens. |
| Better optical quality for high prescriptions: since the corneal surface is not reshaped, the optical aberrations that degrade vision in low light are avoided. | Lifelong endothelial monitoring: over the long term, the presence of the implant can reduce the reserve of endothelial cells. This risk, documented mainly for anterior chamber implants (now abandoned), remains low with posterior chamber implants such as the ICL. A yearly cell count is still essential: it is what would lead, if needed, to removing the implant before the cornea is compromised. |
| Less dry eye: the corneal nerves are not cut, unlike with LASIK. | Strict anatomical requirements: not every eye can take an implant, for lack of sufficient space. |
| Lasting stability: the results hold over time. | A higher cost: the price of the implant is added to the surgeon's fees and to the theatre, anaesthesia and consumables costs. The procedure is not reimbursed by French national health insurance (Assurance Maladie), but a growing number of top-up health insurers (mutuelles) offer a full or partial fixed allowance on presentation of the quote. |
| Reversibility: this is the strongest argument. The implant can be removed or replaced, which no laser surgery allows. | · |
| One of the fastest recoveries: since the cornea is not reshaped, vision becomes functional within 24 to 72 hours and settles within two to six weeks. | · |
A phakic lens can be removed, and that is a real advantage, but removal means another procedure inside the eye, with the same risks as the first. Reversibility is rightly reassuring, because the procedure is not permanent; it should not suggest that the procedure has no consequences.
Complications
They are rare, and the pre-operative assessment is there precisely to reduce them. You should still know about them before choosing this route over laser.
Infection inside the eye, the most serious complication. It requires emergency treatment and can permanently damage vision. The risk is inherent in any surgery that opens the eye, and an antibiotic is injected at the end of the procedure to prevent it.
It can occur through dispersion of iris pigment or closure of the iridocorneal angle, particularly if the implant is too large for the space available. Medical treatment is usually enough; further surgery is sometimes needed.
The endothelium is the inner layer of the cornea: its cells regulate the cornea's hydration, and therefore its clarity, and they do not regenerate. The presence of the implant can speed up their loss. This is why a yearly endothelial cell count is needed, for life.
Contact or rubbing between the implant and the natural lens can encourage premature clouding. It is then treated with cataract surgery, and the phakic lens is removed during the same procedure.
The risk comes more from the high myopia itself than from the implant. You need to know the warning signs and to seek care without delay if you see flashes of light or a shower of floaters.
The choice of size relies on precise biometric measurements, but each person's anatomy keeps an element of unpredictability. An implant that is too large or too small may need to be replaced.
Eligibility criteria
Unlike laser, the phakic lens comes with measured anatomical criteria. These, and not the optical correction alone, decide whether it can be done.
These three measurements (anterior chamber, angle, endothelial density) do not depend on your prescription, your age or your motivation. A highly motivated patient, with myopia perfectly suited to the ICL, can be turned down for an anterior chamber of 2.6 mm. That is why no answer is possible before the assessment.
After the procedure
This is the most concrete difference from laser, and the one least often explained. With corneal surgery, follow-up ends after six months. A phakic lens comes with yearly monitoring, indefinitely.
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, its risks and the consequences of declining treatment. They serve as the basis for informed consent, but do not replace the consultation.
It is often what people have been told elsewhere, but it is not a closed door. The assessment measures your anterior chamber, your angle and your endothelial cell reserve: the three figures that show whether the implant is possible.
Dr Emmanuel Halimi
Ophthalmic surgeon · RPPS 10100555084 · Medical Council of Hauts-de-Seine no. 92/23003
Page written and approved by the surgeon.
Last medical review: