How is the power of an ICL chosen?

Power is calculated from the refraction at the corneal plane, central corneal power, anterior chamber depth and the axial position the lens will occupy. In high myopia a contact lens over-refraction improves accuracy because it measures much closer to the plane the ICL will occupy than a spectacle prescription does. Power is a separate decision from lens size, which determines vault.

What is the difference between EVO ICL and Visian ICL?

The Visian ICL is the earlier generation with no central port, which is why it required a laser peripheral iridotomy before surgery. EVO added the central port, removing that step and the pupillary-block risk it prevented. EVO+ is EVO with a wider optical zone, which reduces night-vision symptoms in eyes with larger pupils.

How is an EVO ICL sized?

The EVO ICL comes in four sizes: 12.1, 12.6, 13.2 and 13.7 mm. Traditional sizing uses white-to-white corneal diameter with a formula or nomogram (OCOS, Reinstein, KS, NK, Parkhurst). These are proxies for the internal anatomy where the lens actually sits, which is why anterior-segment imaging and AI-based methods such as VAULT and VAULT-OCT aim to predict vault directly from the eye's own measurements.

Is EVO ICL better than LASIK?

Neither is better in general; they suit different eyes. EVO ICL removes no corneal tissue and is reversible, which often makes it preferable for higher prescriptions, thinner or irregular corneas, and dry-eye-prone eyes. LASIK and PRK remain excellent for suitable corneas. The right procedure is matched to your anatomy, prescription and goals.

In the three-year FDA prospective multicenter study of 629 eyes, anterior subcapsular cataract occurred in 0.16% of eyes, there were no cases of pupillary block or pigment dispersion, and the safety index was 1.25 at three years. 48.9% of eyes gained a line or more of best-corrected visual acuity.

Am I too old for EVO ICL at 50?

No. On 17 February 2026 the FDA expanded the EVO ICL age indication from 21-45 to 21-60. Many older pages still state 45. Clinically, age still matters because the natural lens loses focusing range over time, so from the late fifties a refractive lens exchange may address both distance and reading vision better than an ICL.

EVO ICL

Name: EVO ICL: Sizing, Vault & Research
Creator: Gurpal Virdi, MD

Why there is so much here about one lens

I have an EVO ICL in my own eyes, and I have implanted them in my own family. You size a lens differently when the patient is your family, or when it is your own vision you are going to live with afterwards.

That is why I spend so much time on sizing. The hard part of this operation is picking the right size lens for a particular eye. Too large and it sits too high, crowding the angle. Too small and it sits too low, close to the natural lens. Nearly every ICL that gets reoperated is reoperated because of that one decision, and the decision is made before the surgery starts.

My published work uses AI and anterior-segment imaging to work out where the lens will actually end up, instead of finding out afterwards. That is also what I built ICL Fit to do. I am a refractive and cataract surgeon from the San Francisco Bay Area and an ICL-sizing researcher, and this is the lens I have gone furthest with.

So there is far more here about one implant than about anything else on the site. That is on purpose.

Gurpal Virdi, MD is an EVO ICL patient himself. Real Surgeon, Real Results With EVO ICL · my own EVO ICL surgery, filmed at Parkhurst NuVision, August 2026. Watch on YouTube.

In short. The EVO ICL is a reversible implantable lens that corrects myopia and astigmatism without removing corneal tissue. It is approved from −3.0 dioptres, so it is a first-line option for most people who wear glasses, not just a fallback for eyes that cannot have laser surgery, and it has particular advantages with thinner corneas and dry-eye-prone eyes. The single biggest driver of a good outcome is choosing the right lens size, which determines vault. That is the problem my research and engineering work is built around.

What is the EVO ICL, and what is it made of?

A soft lens placed in the sulcus behind the iris, in front of your natural lens, which stays where it is. Collamer, the material it is named for, is a copolymer containing purified collagen, which is why the eye never treats it as foreign. Once it is in you cannot see it in a mirror or feel it.

Central port. A 0.36 mm opening through the optic. Aqueous flows through it, which keeps the natural lens nourished and removes the need for a preoperative laser iridotomy. This is what separates EVO from the older Visian generation.
Range. FDA-approved for myopia −3.0 to −20.0 D, toric for 1.0 to 4.0 D of astigmatism, ages 21 to 60.
Blocks UV, by composition, not a coating.
Does not treat hyperopia, or reading vision as you age. That is refractive lens exchange.

Am I a candidate for EVO ICL?

EVO ICL is FDA-approved from ages 21 to 60, for myopia from −3.0 to −20.0 dioptres, with and without astigmatism. That lower bound matters: it covers most people who wear glasses, so this is a first-line option across the range rather than something reserved for very high prescriptions. Beyond age and prescription, candidacy turns on anterior chamber depth, endothelial cell count, angle anatomy, and prescription stability. Some eyes that are turned down for LASIK are excellent ICL candidates, which is why a “no” for laser vision correction is not a “no” for vision correction. See the full candidacy guide.

How EVO ICL is sized

The lens comes in four sizes (12.1, 12.6, 13.2, 13.7 mm), and the same eye can vault very differently across them. Traditional sizing uses white-to-white corneal diameter and single formulas, the OCOS (STAAR) nomogram, the Reinstein formula, the KS formula (Kamiya–Shoji), the NK formula (Nakamura), and the Parkhurst nomogram, each only a proxy for the internal anatomy where the lens actually rests. I co-founded and lead the engineering for ICL Fit, the leading AI ICL-sizing agent, grounded in the peer-reviewed VAULT and VAULT-OCT research (JCRS) and a large, real-world dataset of EVO ICL surgical outcomes, which predicts the best-fit size and post-op vault for each eye from anterior-segment imaging rather than one fixed formula. I trained at Parkhurst NuVision under Dr. Greg Parkhurst, of the Parkhurst nomogram, one of the most-published EVO ICL teams in the U.S.

For patients: for a plain-language guide to EVO ICL, candidacy, recovery, risks, and choosing a surgeon, see ICLSurgery.com, which I co-review.

Watch: ICL sizing methods

An introduction to ICL sizing methods and tips from Matt Hirabayashi, MD, my co-author on the VAULT and VAULT-OCT models.

Also on YouTube and Instagram.

What is ICL vault, and what is a good vault?

Vault is the clearance between the back of the ICL and the front of your natural lens. It follows almost entirely from the size chosen for that eye, so sizing and vault are one problem seen from two ends.

You will see 250 to 750 microns quoted as the target. That is a population range, not a target for your eye. 400 microns can be comfortable in one anterior segment and too tight in another. What counts is clearance relative to that eye's own chamber depth, angle and sulcus. Chasing one number across every patient is how lenses get exchanged.

That is what the AI agents in ICL Fit solve. From that eye's own imaging and the VAULT and VAULT-OCT models, they predict what each of the four sizes would do in that specific anatomy and identify the best fit for that eye, not the size closest to a number borrowed from everyone else.

What happens at the EVO ICL evaluation?

Three separate questions: what power, what size, and whether the eye is a safe place for a lens at all.

Prescription. Autorefraction, manifest and cycloplegic refraction. In high myopia also a contact lens over-refraction, since a spectacle lens sits a centimeter in front of the eye and an ICL does not. A year of documented stability is the usual requirement.
Anatomy. Anterior chamber depth, angle, endothelial cell density, pupil size in the dark, corneal diameter. A shallow chamber, narrow angle or low cell count are real reasons not to implant. High myopes also need a dilated retinal exam.
Imaging. Where practice diverges, and what I would ask about. The lens sits in the sulcus, behind the iris, where light-based scanners cannot see. Much of the field still substitutes white-to-white corneal diameter for the sulcus, a correlation standing in for a measurement. Our work predicts vault from the imaging directly instead.

How is the power of the lens chosen?

Size and power are separate decisions, often confused. Size sets where the lens sits, and therefore vault. Power sets what prescription it corrects, from the refraction at the corneal plane, corneal power, chamber depth and lens position.

Contact lens over-refraction removes most of the vertex-distance error at high powers.
Pick the refractive target deliberately. A −9.00 myope in their 40s may do better with a little residual myopia in the non-dominant eye than plano in both. Decide before the lens is ordered, not after it arrives.

Why do ICLs get exchanged or explanted?

Sizing. A lens that vaults too high or too low for the eye it went into. Our group published the exchange and explant experience of a US high-volume center in Clinical Ophthalmology for that reason: the failure mode is well described and largely predictable, which means it is largely preventable.

Preventing it is what ICL Fit is for. Sizing from white-to-white and a nomogram means inferring the sulcus from the cornea and accepting the error that comes with it. Predicting vault from the eye's own anterior-segment imaging, with models trained on real surgical outcomes, removes most of that error before the lens is ever ordered, and a correctly sized lens is one that does not need exchanging. It is also why I would ask a prospective surgeon how they size, not how many cases they have done.

EVO ICL vs LASIK: which is better?

Neither, in the abstract. EVO ICL removes no corneal tissue and can be taken out, which usually makes it the better answer at higher prescriptions, with thinner or irregular corneas, or in dry eyes. LASIK, PRK and SMILE are excellent in suitable corneas and avoid going inside the eye. The decision is anatomical and imaging settles it.

Full comparison on EVO ICL vs LASIK: prescription range, dry eye, reversibility, recovery, cost.

EVO ICL in the San Francisco Bay Area

I am training in this lens specifically, in a high-volume refractive surgery fellowship at Parkhurst NuVision built around EVO ICL, under Dr. Gregory Parkhurst, principal investigator of the FDA EVO ICL trial, originator of the Parkhurst sizing nomogram, and one of the highest-volume EVO ICL surgeons in the United States. That is a year of ICL cases and, just as importantly, access to a large longitudinal record of real sizing decisions and what they produced. I offer the full spectrum of vision correction: EVO ICL, LASIK, PRK, SMILE, refractive lens exchange and premium cataract surgery.

For Bay Area patients researching EVO ICL now, the practical guidance does not change with geography: ask any prospective surgeon how they choose lens size, what imaging they use, and what their exchange rate is. Patient-facing guides for San Francisco, San Jose and Palo Alto, along with how to choose an ICL surgeon, are on ICLSurgery.com, which I co-review.

What actually happens during EVO ICL surgery?

This operation is remarkably refined now. No cutting in any sense a patient would recognise, no stitches, nothing to remove afterwards. You are awake, on anesthetic drops, usually with a mild oral sedative.

The eye is dilated, because the lens has to pass the pupil, and the surface prepared with povidone-iodine.
A microscopic opening is made at the edge of the cornea, 2 to 3 mm. It is self-sealing, so no sutures.
The lens is rolled into a scroll inside an injector, passed through, and unfolds in the anterior chamber. A protective gel shields the corneal endothelium throughout.
The four footplates are tucked behind the iris into the sulcus, the lens centered, and a toric lens rotated to its planned axis.
The gel is washed out completely, since any left behind is the usual cause of a day-1 pressure spike, and the opening is hydrated closed.

Most people see across the room within minutes of sitting up. That is a dilated eye through a slightly swollen cornea, so not the final result, but usually enough to be startling.

How long does EVO ICL surgery take?

Quoted anywhere from 5 to 30 minutes. Surgeons are not disagreeing, they are timing different things.

The implantation itself: about 3 minutes per eye in experienced hands. This is the part people picture.
In the operating room: roughly 15 minutes per eye, adding positioning, draping, drops, the surgical pause and washing out the gel.
At the facility: 2 to 3 hours, including check-in, dilation, the procedure and a pressure check before you leave.

That last one is the number that determines your day, and almost nobody advertises it. Ask how long you will be at the facility, not how long the surgery takes.

EVO ICL recovery, day by day

Day 1. Useful vision, and most people are back at a desk. Pressure and vault checked within 24 hours.
Week 1 and month 1. Routine checks. Antibiotic and anti-inflammatory drops run 1 to 4 weeks on a taper.
First 2 weeks. No rubbing, no pools or hot tubs. Eye protection for contact sport.
Halos at night are common early and usually settle as the visual system adapts, more so with large pupils. Expected, not a complication.

The number your surgeon watches at every visit is the vault, measured on anterior-segment OCT. It is the direct consequence of the size chosen before the operation started.

How safe is EVO ICL? What the data actually shows

Very safe, and here are the numbers rather than the adjective. From the 3-year FDA study of 629 eyes across 14 US sites:

Cataract: 0.16% of eyes. About 1 in 625. For scale, the same highly myopic eyes carry a lifetime risk of retinal detachment several times that, with or without any surgery at all.
Pupillary block: 0 cases. Pigment dispersion: 0 cases. The central port is why.
Safety index 1.25. Eyes saw better after surgery than they had with their best glasses before it.
48.9% gained a line or more of best-corrected acuity (PubMed).

A larger surveillance review of 17,482 FDA adverse-event reports (2015 to 2023) found over 70% recorded no clinical signs at all. Read those percentages carefully: they are proportions of reports, not rates, because the dataset has no denominator of total implants (full text).

The one complication a surgeon actually controls is sizing. Our review of exchanges and explants found sizing, not the lens or the technique, drives the reoperations that do happen (Clinical Ophthalmology, 2025). Ask how a surgeon sizes, not just how many cases they have done.

Am I too old for EVO ICL?

Probably not, and the answer changed recently. On 17 February 2026 the FDA raised the age indication from 21 to 45 out to 21 to 60 (STAAR). Plenty of well-ranking pages still say 45, so advice you were given before then is out of date.

Age still matters clinically, just not as a cutoff. From your late 40s the natural lens is losing its focusing range, so an ICL fixes distance and does nothing for reading. By the late 50s a refractive lens exchange often serves you better by treating both at once. That is a conversation about your lens, not your birthday.

Does an EVO ICL rule out other eye surgery later?

No. Because the lens is additive and removable, it leaves your options open rather than closing them.

Laser enhancement is possible. A small residual error, usually a fraction of a dioptre, can be treated on the cornea afterwards (bioptics). The ICL does the heavy lifting and the laser tidies up, using far less corneal tissue than treating the whole prescription would have.
Cataract surgery later is unaffected. The ICL is removed at the start and the natural lens replaced as usual. It does not distort the IOL power calculation the way previous LASIK or PRK does, because the cornea was never altered. That is a real long-term advantage.
The lens itself can come out. If your eyes or circumstances change, it is removed or exchanged and the eye returns close to where it was. Removed corneal tissue cannot be put back.

EVO ICL vs Visian ICL and EVO+: what is the difference?

Three names, one sequence rather than three options.

Visian ICL. The earlier generation, no central port, which is why it needed a laser iridotomy first.
EVO ICL. Added the central port, removing that step and the pupillary-block risk it prevented.
EVO+. EVO with a wider optical zone, which reduces night-vision symptoms in larger pupils.

If you are offered an ICL in the US today it is an EVO or EVO+. One caveat we published on directly: the labeled diameter of these lenses is not exactly what is measured. Our Cureus study found discrepancies between reported and measured sizes, which matters because sizing assumes the number on the box is the number in the eye. One more reason to predict vault from the eye's own anatomy. The paper is here.

Does the EVO ICL block UV light?

Yes. The Collamer contains a bonded UV-absorbing chromophore, so the optic filters UVA and UVB. It is in the material, not a coating, so it cannot wear off.

That matters because cumulative UV contributes to cortical cataract and is implicated in pterygium. Your natural lens absorbs plenty of UV itself, which is part of why it yellows with age. An ICL in front of it takes some of that load.

It does not replace sunglasses. The optic is a small disc behind the pupil, so it filters light through the pupil and nothing else: not the conjunctiva, cornea, eyelids or surrounding skin, and not light entering obliquely around the iris edge. Wraparound sunglasses cover all of that.

Where this training comes from

Parkhurst NuVision is one of the highest-volume EVO ICL centers in the country, so the fellowship is not only a high-volume surgical year. It is access to a large longitudinal record of real sizing decisions and the vaults that followed them. The VAULT and VAULT-OCT models were built on exactly that kind of data, and the exchange and explant paper came from asking what actually goes wrong and how often. Training somewhere that keeps that record is what makes it possible to study sizing instead of just having an opinion about it.

I have co-authored peer-reviewed EVO ICL research with Dr. Parkhurst and the Parkhurst NuVision group in the Journal of Cataract & Refractive Surgery, Clinical Ophthalmology and Cureus, covering AI vault prediction, sizing-driven exchanges, outcomes in shallow anterior chambers, and the labeled-versus-actual dimensions of the lenses themselves. Listed below.

My EVO ICL research

Peer-reviewed research I've co-authored on EVO ICL sizing, vault prediction, and outcomes:

VAULT-OCT: Predicting ICL Postoperative Vault from AS-OCT Using Deep Learning
Journal of Cataract & Refractive Surgery (JCRS), 2025
DOI PubMed
VAULT: A Novel Image-Based AI Model for Predicting ICL Postoperative Vault
Journal of Cataract & Refractive Surgery (JCRS), 2024
DOI PubMed
ICL Exchanges or Explants Due to Sizing in a US High-Volume Center
Clinical Ophthalmology, 2025
DOI PubMed Full text
Clinical Outcomes of ICL for Myopia in Eyes with ACD < 3.0 mm
Clinical Ophthalmology, 2025
DOI PubMed Full text
Accuracy of Reported Sizes of the EVO/EVO+ Visian ICL
Cureus, 2025
DOI PubMed
Dynamic Changes in ICL Vault and Angle Under Varying Lighting
Clinical Ophthalmology, 2026
DOI PubMed

More research, including the tools built from it, is on ICLSurgery.com/research and ICL Fit.

In the media

AI Is Reshaping ICL Size Selection
Ophtho Biz Minute (@ophthobizminute), featuring Gurpal Virdi, MD on why sizing is the single most consequential decision in ICL surgery
Instagram

By location

EVO ICL in San Francisco
How the lens is sized, and the three questions worth asking any San Francisco surgeon.
EVO ICL in Palo Alto
For the Peninsula: Menlo Park, Mountain View, Redwood City, Los Altos.
EVO ICL in San Jose
Santa Clara, Sunnyvale, Cupertino and the wider Silicon Valley.

Common questions, answered in depth

Can you get EVO ICL over 45?
The FDA raised the age limit to 60 in February 2026. Most pages still say 45.
Is EVO ICL safe?
The three-year FDA trial numbers, the surveillance data, and what the percentages actually mean.
How much does EVO ICL cost?
What drives the price, what should be included, and the line item worth more than a discount.

Common questions

Does the EVO ICL block UV light? Yes. The Collamer contains a bonded UV-absorbing chromophore, so the optic filters UVA and UVB permanently. It protects only the pathway through the pupil, so sunglasses are still needed for the ocular surface, lids and obliquely entering light.

Can I have LASIK after an ICL? Yes. A small residual refractive error can be treated with a surface laser procedure afterwards, an approach called bioptics.

Can I have cataract surgery after an ICL? Yes. The ICL is removed at the start of the operation and the natural lens replaced as usual. Unlike previous LASIK or PRK, an ICL does not distort the intraocular lens power calculation, because the cornea was never altered.

Has Dr. Virdi had EVO ICL himself? Yes. Gurpal Virdi, MD is an EVO ICL patient himself, and has implanted the lens in members of his own family.

What is the EVO ICL made of? Collamer, a hydrophilic copolymer containing purified collagen, which the eye tolerates without an immune response and which blocks ultraviolet light.

What prescriptions can the EVO ICL treat? Myopia from −3.0 to −20.0 dioptres, with the toric version correcting 1.0 to 4.0 dioptres of astigmatism alongside it. It does not treat hyperopia.

Do I need a laser iridotomy before EVO ICL? No. The central port in the EVO optic allows aqueous to flow, which is what the iridotomy used to accomplish for the older Visian generation.

How long is the recovery after EVO ICL? Useful vision is typically present the next day, with drops for roughly one to four weeks and follow-up at day one, one week and one month.

What is the difference between EVO and EVO+? EVO+ has a wider optical zone, which helps reduce night-vision symptoms in eyes with larger pupils. Both have the central port.

What is a good ICL vault? 250 to 750 microns is the rule of thumb, but it is a rough band averaged across everybody, not a target for your eye. The same 400 microns can be comfortable in one anterior segment and too tight in another. What matters is the fit for your own anatomy, which is what ICL Fit predicts from your imaging.

How long does an EVO ICL last? It is designed to stay in place indefinitely, and it can be removed or exchanged if your eyes or needs change. That reversibility is one of its main advantages over corneal laser surgery.

Does EVO ICL cause dry eye like LASIK? Because no corneal nerves are cut, EVO ICL is generally the preferred option in eyes already prone to dry eye.

Can EVO ICL correct astigmatism? Yes. The toric EVO ICL corrects astigmatism alongside myopia; correct alignment as well as correct sizing matters for the result.

Is there a calculator for ICL size? ICL Fit is the AI sizing agent I co-founded, built on the peer-reviewed VAULT and VAULT-OCT models rather than a single formula.

Get in touch

Sizing, vault, and the research, by Gurpal Virdi, MD · San Francisco Bay Area, California

Medically reviewed by Gurpal Virdi, MD, refractive and cataract surgeon and ICL-sizing researcher · Last reviewed: 15 September 2026

Educational information, not medical advice. Discuss your specific eyes with a qualified ophthalmologist.