Short answer
An implantable collamer lens (ICL) is a thin, flexible lens placed inside the eye, between the iris and the eye’s own lens, to correct short sight and astigmatism. Unlike laser eye surgery, it adds a lens rather than removing corneal tissue, and it can be taken out if needed. It is mainly considered for adults with higher prescriptions or corneas unsuitable for laser, and suitability depends on the space inside the eye, the health of the cornea’s inner cell layer and a stable prescription.
Key points
- An ICL is a type of phakic intraocular lens: it works alongside the eye’s natural lens.
- It treats short sight and astigmatism, including higher degrees than LASIK can.
- Typical candidates are adults in their 20s to mid-40s with a stable prescription.
- For moderate to high short sight, trials found less loss of best-corrected vision than with laser.
- Risks include raised eye pressure, early cataract, infection and loss of corneal inner cells.
- It does not prevent the need for reading glasses with age.
What an ICL is
“Phakic” means the eye keeps its natural lens. A phakic intraocular lens is an additional lens implanted inside the eye to correct a refractive error (a focusing problem)3. The ICL is one such lens, positioned behind the iris (the coloured part of the eye) and in front of the natural lens12.
Collamer is a material that combines plastic and collagen, and is lighter and more flexible than some other lens materials1. A newer version, the EVO ICL, has a small central opening that allows fluid to flow and has largely removed the need for a preliminary laser opening in the iris12.
How it differs from laser eye surgery
| Feature | ICL | Laser surgery (LASIK, PRK, SMILE) |
|---|---|---|
| How it works | Adds a lens inside the eye1 | Removes corneal tissue to reshape the cornea5 |
| Reversible | Lens can be removed or exchanged12 | Tissue removal cannot be undone |
| Suited to thin or irregular corneas | May be an option2 | Often not suitable |
| Surgery inside the eye | Yes, with risks such as infection inside the eye1 | No; treatment is confined to the cornea |
| Moderate to high short sight (trial evidence) | Less loss of best-corrected vision at 12 months; preferred by patients4 | Similar uncorrected vision at 12 months4 |
Who may be considered
Academic medical centres describe typical candidates as short-sighted adults aged roughly 21 or 22 to 45, with a prescription that has been stable for about a year12. It may be considered for higher short sight that other procedures cannot correct, and for people who are not suitable for LASIK because their corneas are thin or irregular2.
The eye’s internal anatomy must also fit. A shallow front chamber of the eye or a low density of endothelial cells (the single layer of cells that keeps the cornea clear) makes someone a poor candidate, and a history of iritis (inflammation inside the eye), glaucoma or diabetic eye disease counts against it. People who are pregnant or breastfeeding are advised to wait2.
Procedure and recovery
The eye is numbed with drops or local anaesthetic, sometimes with mild sedation. The folded lens is inserted through a very small incision at the edge of the cornea, usually without stitches, and surgery is short12. Eye pressure and lens position are checked within hours, with follow-up the next day and over the following months2.
Vision often improves within 24 hours, with full improvement taking about a week to 10 days, and eye drops are usually needed for around two weeks1. Annual check-ups are then recommended2.
What the evidence says about results and risks
A Cochrane review of three randomised trials (228 eyes) in people with short sight of 6 to 20 dioptres compared phakic lenses with excimer laser surgery. At 12 months, uncorrected vision was similar, but phakic lenses caused significantly less loss of best spectacle-corrected vision, gave better contrast sensitivity and were preferred by patients4. The trials were small, followed people for only a year, and many lenses studied have since been superseded4: Moderate for short-term outcomes, Limited for long-term safety.
An American Academy of Ophthalmology technology assessment found phakic lenses effective, with acceptable short-term complication rates, but highlighted long-term concerns: loss of endothelial cells, cataract formation, secondary glaucoma from raised pressure, and dislocation after injury. It also noted a lower risk of retinal detachment than with refractive lens exchange3. Other listed risks include bleeding, infection, inflammation inside the eye, halos and glare, and temporary raised eye pressure1.
Because endothelial cells do not regenerate, regular monitoring after an ICL matters. Long-term safety data on current lens designs are still developing: Limited.
When to seek medical advice
Because an ICL involves surgery inside the eye, infection and raised eye pressure are recognised risks1. Eye pressure and lens position are checked within hours of surgery and again the next day for this reason2, so these early checks should not be missed. Any new symptom after surgery should be raised with the treating eye team without delay.
Common questions
Can an ICL be removed?
Yes; it can be surgically removed or replaced, for example if the prescription changes markedly or a cataract develops12.
Will I still need reading glasses?
Probably, eventually; an ICL does not treat presbyopia (age-related loss of close focus), so people over about 40 may still need reading glasses2.
Is an ICL safer than laser surgery?
For moderate to high short sight, short-term trials favoured phakic lenses on loss of best-corrected vision4, but the risks are different in kind, including intraocular surgery and long-term endothelial cell loss3.
Is an ICL available on the NHS?
Usually not; the NHS says lens surgery to correct vision is usually only available privately5.
Bottom line
An ICL corrects vision by adding a removable lens rather than reshaping the cornea, which makes it an option for some people with high short sight or corneas unsuited to laser. It brings the risks of surgery inside the eye and needs lifelong monitoring, so careful measurement of the eye’s internal space and corneal cells comes first.
Related reading
- Eye surgery
- Who May Not Be Suitable for Laser Eye Surgery?
- What Is Refractive Lens Exchange?
- LASIK vs SMILE: What Is the Difference?
Sources
- Cleveland Clinic. Implantable collamer lens (ICL) surgery. Cleveland Clinic. https://my.clevelandclinic.org/health/treatments/25050-implantable-collamer-lens-icl-surgery. Accessed 5 November 2026.
- Michigan Medicine, University of Michigan. Phakic intraocular lenses (IOLs) or implantable contact lenses (ICLs). University of Michigan Health. https://www.uofmhealth.org/our-care/specialties-services/phakic-intraocular-lenses-iols-or-implantable-contact-lenses-icls. Accessed 5 November 2026.
- Huang D, Schallhorn SC, Sugar A, Farjo AA, Majmudar PA, Trattler WB, Tanzer DJ. Phakic intraocular lens implantation for the correction of myopia: a report by the American Academy of Ophthalmology. Ophthalmology; 2009;116:2244-2258. https://www.aao.org/ophthalmic-technology-assessment/phakic-intraocular-lens-implantation-correction-of. Accessed 5 November 2026.
- Barsam A, Allan BDS. Excimer laser refractive surgery versus phakic intraocular lenses for the correction of moderate to high myopia. Cochrane Database of Systematic Reviews; 2014;(6):CD007679. https://doi.org/10.1002/14651858.CD007679.pub4.
- NHS. Laser eye surgery and lens surgery. NHS website; reviewed 2024. https://www.nhs.uk/tests-and-treatments/laser-eye-surgery-and-lens-surgery/. Accessed 5 November 2026.
Article history
- — First published.