There is a sentence I now hear often in my clinic: "Somewhere else they told me I am not suitable for laser." In the voice of the patient saying it there are usually two things at once — disappointment, and a small suspicion: "Did they say that to sell me ICL, or am I really not suitable?" I want to answer this question honestly: no, being found unsuitable for LASIK does not automatically mean you are suitable for ICL. ICL has its own measurement criteria, its own reasons for refusal and its own need for long-term follow-up.
In this article I will first explain why laser (LASIK, SMILE, PRK) may have ruled you out, then ICL's own limits, and finally why the check-ups do not end after the operation. My aim is not to steer you towards a method, but to share the information and literature I have as they are.
Short answer: ICL is not a "back-up option" but a separate decision with its own rules
ICL (implantable lens) is not a back-up plan that automatically kicks in for people who cannot have laser. It is a decision in its own right, with its own measurement criteria, its own postoperative follow-up programme and its own limits. If laser was found unsuitable for you, this usually comes from a limit related to your cornea — and because ICL does not touch the cornea, it often takes that limit out of play. But "often" is not the same as "always"; there are situations in which ICL can close its own door too, and the second half of this article is about exactly those.
First let us be clear: why were you found unsuitable for LASIK (or SMILE/PRK)?
When you hear "you are not suitable for laser", the first question that comes to mind is probably "why". The answer to this question almost always rests on one of three or four headings, sometimes a combination of two.
If the cornea is not thick enough
LASIK, SMILE and PRK all change the angle at which light is refracted by removing tissue from the cornea. After this procedure, the corneal tissue left behind needs to be thick enough to remain structurally safe against the pressure inside the eye. If the cornea already measures thin before surgery, or your prescription requires reshaping that is too deep for that thinness, your doctor will not recommend laser rather than push this limit. This is not a preference; it is a safety limit set to prevent permanent weakening of the cornea (the risk of ectasia).
If the prescription is outside the range laser can safely correct
Each laser method gives predictable and stable results within a certain prescription range. If your prescription is close to or beyond the upper limit of this range, the required reshaping depth may exceed what the cornea can bear. In such a case laser is not "impossible", but it is not recommended — because we cannot be sure of the safety and permanence of the result.
If pupil size increases the risk to night vision
Especially in eyes whose pupils dilate markedly in the dark, light rays that spill outside the zone reshaped by laser can cause halos and night vision disturbance. This is not seen to the same degree in everyone; it is determined by measurement, and in some patients it leads us to discuss another method instead of laser.
Anterior chamber depth (ACD) is also measured — but it does not decide on laser
There is a small but important distinction here that I want to state honestly: anterior chamber depth is not actually a measurement that directly rules out laser itself. But it is routinely measured in the same comprehensive examination — because in an eye found unsuitable for LASIK, the next question is usually "so can I have ICL?", and the answer to that question depends to a large extent on anterior chamber depth. So this measurement decides not the laser question, but the next step.
Do not just accept "you are not suitable for laser" with a single reason; ask which measurement set the limit. Corneal thickness and the prescription limit often bring ICL up automatically; but no decision is made without ICL's own criteria being assessed separately.
What is ICL, and where does it sit in the eye?
ICL (Implantable Collamer Lens / implantable lens) is a thin, soft lens placed just behind the iris (the coloured layer of the eye) and in front of your own natural lens, without touching the cornea at all. It corrects your refractive error not by reshaping the cornea, but by adding extra optical power inside the eye.
It does not touch the cornea — why this matters
This difference is the exact counterpart to why you were found unsuitable for LASIK: if the cornea is thin or the prescription is too high for laser, the problem is in the cornea. Because ICL does not touch the cornea at all, it largely takes these two restrictions out of play. Current models with a small hole (port) in the centre are designed to allow the natural circulation of fluid inside the eye; in a review of 27 studies and 2,204 eyes, complications with these models were rare and no sight-threatening event was reported.[1]
ICL has its own limits too: who is not suitable for ICL either
Just as LASIK has its own safety limits, ICL has its own acceptance and refusal criteria. I will not give the exact numerical thresholds of these criteria measured by your doctor here — they are calculated specifically for your eye, and the suitability tool on our site does this calculation with your measurements. But knowing which headings are assessed helps you understand why so many measurements are taken.
If the anterior chamber is too shallow
ICL sits in a particular space in front of your natural lens and behind the iris. If this space (the anterior chamber) is not deep enough, the lens sits too close to the endothelial cells on the inner surface of the cornea; this can accelerate endothelial cell loss over time. A recent review shows that in eyes whose anterior chamber becomes shallower over time, endothelial cell loss over ten years of follow-up can reach about twice the rate expected from physiological ageing.[2] That is why in eyes with a shallow anterior chamber ICL is either not recommended or is monitored at much more frequent intervals.
If the endothelial cell count is low
The cornea keeps its transparency with the single layer of endothelial cells on its inner surface; these cells do not renew themselves, and their number can only decrease. If your endothelial cell count before surgery is already borderline low, we do not want to add a further load to ICL's normal physiological loss — in this case the operation is either postponed or another method is discussed.
If there is early cataract, glaucoma or an irregular cornea
ICL sits just in front of your natural lens; if your lens shows signs of early cataract, ICL may complicate the management of the cataract later rather than masking it. Similarly, uncontrolled glaucoma or an irregular corneal structure (such as keratoconus) requires a separate and more careful assessment — in these patients the decision becomes entirely individual.
In pregnancy, breastfeeding, and an unstable prescription
Because hormonal fluctuations during pregnancy and breastfeeding can cause temporary changes in corneal and intraocular measurements, ICL is not planned in this period. Likewise, if your prescription is still changing markedly over the past year, we first wait for the prescription to settle — the lens is made individually according to the measurements at that time, and if the prescription changes later, another operation may be needed.
Do not rule out the possibility "I am not suitable for ICL either" from the start. If there is a shallow anterior chamber, a low endothelial cell count or signs of early cataract, it is best to discuss this openly first and then decide on the method.
Which measurements are done before ICL?
The ICL decision is not made in a single examination. Many measurements come together, such as corneal mapping (topography), anterior chamber depth, white-to-white distance (corneal diameter), endothelial cell count and pupil size; each of these answers both "can I have ICL?" and "which lens size?".
Why vault calculation and lens sizing are planned work, not a one-off
Vault is the space between the back surface of the implanted lens and your own natural lens. This space should be neither too narrow nor too wide: if it is narrow, the lens may touch the natural lens and accelerate cataract; if it is wide, it may push the iris forward and affect eye pressure. Lens size is calculated from the measurements, but it is not possible to predict exactly in advance how the vault will behave after surgery — that is why the first check-ups are done at close intervals. A study following 47 eyes of 26 patients for ten years showed that the vault decreased over time along a predictable curve, and that this curve could be modelled mathematically.[3]
Follow-up does not end when the operation does
After LASIK, follow-up is largely complete within a few months. With ICL the situation is different: because the lens is a permanent structure inside the eye, follow-up also becomes permanent. I always tell my patients this with the same clarity: ICL is an option, but not one to take with your eyes closed.
Why eye pressure (IOP) is monitored regularly
Because the lens adds extra volume inside the eye, it can affect drainage of the fluid inside the eye. In the same study following 47 eyes for ten years, mean eye pressure went from 14.8 mmHg before surgery to 15.4 mmHg at year 10, i.e. it remained stable; in the same series no sight-threatening complication such as pupillary block or pigment dispersion glaucoma was seen.[3] But this stability is not automatic; it is a result maintained by regular measurement — which is why I ask you not to skip check-ups.
Endothelial cell count — why it is repeated once a year
Because endothelial cells do not renew themselves, their loss is irreversible; the aim is not to bring the loss to zero but to make sure it does not exceed what is expected. In the same ten-year series, total endothelial cell loss was measured at 6.8%[3]; in eyes whose anterior chamber was already borderline at the start, this loss can be more marked — in a separate study following 41 eyes for 7.76 years, endothelial cell density decreased by 9.39% (mean annual loss 30.24 cells/mm²).[4] The difference between the two rates is not a coincidence: the second group consists of eyes operated on with a borderline anterior chamber depth — a good example of why follow-up is intensified according to the person.
Vault change and future cataract risk
Vault tends to decrease over time; the reason for monitoring it is that an excessively reduced vault can come into contact with the natural lens and accelerate cataract. In the same 41-eye, 7.76-year follow-up study, peripheral anterior subcapsular cataract developed in three eyes (7.31%)[4] — this is a rate measured in a subgroup whose anterior chamber was already borderline at the start, and it cannot be generalised to the whole ICL population. In a broader comparative analysis, cataract development rates between ICL and a similar type of phakic lens were between 0.7% and 0.8%, very close to each other and low; in the same study endothelial cell loss was also measured at 2.2% in both groups.[5] So the risk of cataract is real and needs to be monitored — but its size is a personalised number that varies with your preoperative measurements.
The follow-up programme I apply is this: more frequent in the first year, then at least once a year eye pressure, endothelial cell count and vault measurement. These check-ups are not a formality; they are the only way to show how the lens coexists with your eye over the long term.
Are ICL and laser methods rivals, or complementary?
The distinction I have described throughout this article is actually simple: LASIK, SMILE and PRK reshape the cornea; ICL adds a lens inside the eye without touching the cornea. Neither is "better" than the other — they offer different solutions to different problems. In a large systematic review of posterior chamber phakic intraocular lenses (92.7% of the eyes studied had been operated on with V4c, the most widely used ICL model today), complication rates were examined across 45,027 eyes: lens rotation or displacement occurred at 4.2 per 1,000 patient-years, and removal of the lens (explantation) at 3.1 per 1,000 patient-years — roughly meaning rotation in about 2 and removal in about 2 of 100 eyes over five years of follow-up. More serious complications such as retinal detachment and macular oedema were much rarer (0.4 and 0.3 per 1,000 patient-years, respectively).[6] These rates are low, but not zero; that is how I explain it to my patients too: rare but real.
My preference in practice is to decide the method not by "which is more popular", but by your corneal thickness, anterior chamber depth and prescription.
Would you like to compare LASIK, SMILE and PRK side by side?
Compare LASIK, SMILE and PRK (in Turkish) →Patients who have previously had laser and whose prescription has shifted somewhat also often ask: how does this risk change with ICL? I have covered this in a separate article: why the prescription can come back after laser, and how this risk changes with ICL
How can you find out where you stand?
Each of the criteria I have described — corneal thickness, prescription, pupil size, anterior chamber depth, endothelial cell count — combines with a different weight in your eye. I would not want you to calculate them one by one yourself; the interactive suitability tool on our site calculates, from your own measurement values, which of LASIK, SMILE, PRK and ICL may suit your eye.
Would you like to find out whether you are suitable for ICL with your own corneal and prescription values?
Test for free whether you are suitable for ICL with your own corneal and prescription values (in Turkish) →Frequently asked questions
No, they are separate assessments. The reason you were found unsuitable for LASIK is usually corneal thickness or the prescription range; because ICL does not touch the cornea, it takes these two restrictions out of play. But ICL's own criteria — such as anterior chamber depth and endothelial cell count — are assessed separately and carefully.
The lens is designed to be permanent but it is not irremovable; when necessary (for example if your prescription changes markedly or cataract develops) it can be surgically removed or replaced. In a large review the lens removal rate was measured at 3.1 per 1,000 patient-years — a low but non-zero likelihood.
Yes, there is, and it is a real risk that needs to be monitored. The rates vary from study to study: a broad comparative analysis found low rates such as 0.7-0.8%, while in a subgroup whose anterior chamber was borderline at the start the rate rose to 7.31% over 7.76 years of follow-up. This difference is directly related to your preoperative measurements — which is why I recommend regular check-ups.
Because ICL, unlike laser methods, does not remove tissue from the cornea, corneal thickness is not as decisive in the ICL decision as it is for laser. But corneal health — such as its shape and endothelial cell count — remains part of the overall assessment.
Yes, they are essential. The programme I apply involves more frequent intervals in the first year, then at least once a year eye pressure, endothelial cell count and vault measurement; in the literature, too, long-term regular follow-up is standard practice. This is the only way to show how the lens coexists with your eye over the years.
No, it is not suitable for everyone. ICL is not recommended, or is postponed, in eyes with a very shallow anterior chamber, a low endothelial cell count, early cataract or uncontrolled glaucoma, during pregnancy or breastfeeding, or where the prescription has not yet settled.
The price varies with the type of lens (toric or not), the lens size made individually according to your eye's measurements, and any additional needs that emerge during the assessment. Rather than giving a fixed figure, I prefer to give you specific information once your exact needs have become clear at the examination.
References
- Larivoir et al. "Efficacy, Predictability, and Safety of Phakic Implantable Collamer Lenses V4c and V5: A Systematic Review and Meta-analysis." Journal of Refractive Surgery, 2025. PMID 41369665
- Watanabe K. "Anterior Chamber Depth and the Long-Term Safety of Implantable Collamer Lens Surgery: A Case for Re-Evaluating Age-Stratified Indication Criteria." Clinical Ophthalmology, 2026. PMID 42707484
- Nakamura et al. "Vault Decay Prediction Formula for Posterior Chamber Phakic Intraocular Lens With Central Hole Implantation: A 10-Year Follow-Up Study." American Journal of Ophthalmology, 2026. PMID 41642700
- Kong et al. "Long-term Efficacy and Safety of the Implantable Collamer Lens in Eyes With an Anterior Chamber Depth of 2.6 to 2.8 mm." Journal of Refractive Surgery, 2026. PMID 42715015
- Rodrigues Alves et al. "Efficacy and safety of implantable phakic contact lens versus implantable collamer lens in myopic eyes: a systematic review and meta-analysis." Journal of Cataract & Refractive Surgery, 2026. PMID 42312551
- Passaro et al. "Potential Harms of Posterior Chamber Phakic IOL: A Systematic Review and Meta-Analysis of Complication Incidence." American Journal of Ophthalmology, 2026. PMID 41611001
The right method becomes clear according to your eye.
Let us clarify together why you were found unsuitable for LASIK and whether ICL is really an option for you.