Is ICL implantation safer because it does not involve removing corneal tissue?

 

Based on evidence available at the one-year follow-up, ICL implantation was found to be safer than corneal laser surgery in certain respects. A Cochrane review combining three randomized controlled trials involving 228 eyes found that ICL implantation was associated with significantly fewer losses of best-corrected visual acuity [1]. However, this safety assessment was not based on superior visual outcomes. In the same review, there was no statistically significant difference between the two procedures in the proportion of patients achieving uncorrected visual acuity of 20/20 or better at 12 months [1].

A question like this often appears on Korean Q&A platforms:

"I've looked into it, and I've found quite a lot of posts from people who had their implants removed due to side effects. I'm currently 24. If I undergo ICL implantation, could I end up needing the lenses removed in my 40s because of insufficient corneal endothelial cells or the development of cataracts?"

Where exactly is the lens implanted, and what does the procedure involve?

ICL implantation is a procedure in which a corrective lens is placed inside the eye, in front of the natural crystalline lens, which remains intact. The Korea Disease Control and Prevention Agency (KDCA) also lists phakic intraocular lens implantation alongside laser surgery as a surgical option for myopia [3].

Preserving the natural crystalline lens is what distinguishes ICL implantation from cataract surgery. During cataract surgery, the cloudy natural lens is removed and replaced with an artificial intraocular lens.

There are two possible locations for lens implantation: the anterior chamber, in front of the iris, and the posterior chamber, between the iris and the natural crystalline lens [1].

This is fundamentally different from corneal laser surgery. While laser procedures reshape the cornea to reduce its refractive power, ICL implantation uses an artificial lens to redirect light so that it focuses on the retina [1].

What exactly does the one-year evidence tell us?

The one-year evidence suggests that ICL implantation may carry a lower risk of losing vision.

The Cochrane review included three trials involving 228 eyes. Participants had myopia ranging from -6.0D to -20.0D, including cases with astigmatism of up to 4.0D [1].

At the 12-month follow-up, the ICL group had significantly fewer losses of best-corrected visual acuity [1]. Best-corrected visual acuity refers to the level of vision achieved with optimal spectacle correction.

Contrast sensitivity was also better in the ICL group [1]. Contrast sensitivity is the ability to distinguish objects with subtle differences in brightness.

Patient satisfaction questionnaires likewise showed higher scores for ICL implantation [1].

Does ICL implantation have any disadvantages?

The Cochrane review also noted a risk of early cataract development following ICL implantation. Specifically, it identified a low risk of cataracts developing at an earlier stage [1].

The size and limitations of the evidence should also be considered. These conclusions were based on only three trials involving 228 eyes, and the authors noted that further trials with sufficient statistical power for subgroup analyses were needed [1].

The follow-up period was also limited to one year. The authors concluded that long-term safety data should be considered as they become available [1].

Could cataracts develop 20 years after ICL implantation?

The longest follow-up data currently available in the cited studies extend to eight years.

A study following 177 eyes in 106 patients over eight years reported cataract development in three eyes, representing 1.7% of the total [2].

There was a common finding among all three cases: each eye had shown mild peripheral anterior subcapsular cataract changes even before surgery [2].

The subsequent treatments were also documented. In some cases, the implanted lens was removed together with cataract surgery at the two- or three-year follow-up. In another case, the lens was exchanged for one size larger at the seven-year follow-up [2].

Will corneal endothelial cells decrease after ICL implantation?

No significant reduction in corneal endothelial cell density was observed during the eight-year follow-up.

The eight-year study reported no cases of significant endothelial cell loss throughout the observation period [2].

Corneal endothelial cells form a layer on the inner surface of the cornea. They help maintain corneal clarity by pumping excess fluid out of the cornea. Once these cells are lost, they do not regenerate.

Intraocular pressure was also monitored. No cases of significant pressure elevation, including pupillary block, were reported during the eight-year follow-up [2].

How reliable is the eight-year follow-up data?

The eight-year follow-up study was retrospective, meaning that it reviewed previously collected medical records rather than being a randomized controlled trial [2].

This represents a different level of evidence from the randomized trials included in the Cochrane review.

The study also disclosed a potential conflict of interest. One of the authors was listed as a paid consultant to the lens manufacturer [2].

This does not mean the findings should be disregarded, but neither should they be interpreted as stronger evidence than the study design allows. The eight-year results should be understood within these limitations.

Did the refractive correction remain stable over eight years?

Refractive outcomes remained generally stable over the eight-year period.

At the eight-year follow-up, 83% of eyes were within ±0.5D of the target refraction, while 93% were within ±1.0D [2].

The degree of change was also relatively small. The average refractive shift between one month after surgery and the eight-year follow-up was -0.13D [2].

The participants had moderate to high myopia, with an average preoperative refractive error of -7.99D [2].

Can the implanted lens be removed later?

The eight-year follow-up study documented actual cases in which implanted lenses were removed.

In some of the three eyes that developed cataracts, the ICL was removed at the same time as cataract surgery was performed [2].

However, these procedures were carried out because a medical indication, namely cataract development, had arisen.

These cases should not be interpreted as evidence that ICL implantation can simply be reversed at any time without consequences.

The study did not provide data on visual outcomes following lens removal alone. If you want to understand what happens to vision after an ICL is removed, this is an important point to discuss during your consultation.

Which should you choose: ICL implantation or corneal laser surgery?

The choice depends on factors such as your refractive error and corneal thickness.

The Cochrane review concluded that, for myopia ranging from -6.0D to -20.0D, ICL implantation was safer in certain measured outcomes and was preferred by patients [1].

The authors also discussed a broader range of potential applications. While ICL implantation was already an established option in routine clinical practice for patients with a spherical equivalent of 7.0D or higher, they suggested that it could also be considered for moderate myopia below 7.0D [1].

A comparison of different corneal laser procedures is available in our article about SMILE LASIK. That review found no significant differences in visual outcomes between the procedures examined [4].

What should you ask during your consultation?

The most important things to check are your individual eye measurements and the long-term monitoring plan.

Here are some key questions to discuss with your ophthalmologist:

• What is my current corneal endothelial cell count, and how frequently should it be monitored?

• Is there already any lens opacity, and if so, where is it located? [2]

• Is there sufficient space inside my eye for an ICL?

• What measurements are used to determine the appropriate lens size?

• Is corneal laser surgery also a suitable option for my prescription? If not, which measurements make me unsuitable?

• If the implanted lens needs to be removed in the future, what treatment options would be available? [2]

There is another important distinction that is easy to overlook when comparing ICL implantation with cataract surgery.

The selection of artificial lenses used to replace the natural crystalline lens during cataract surgery is covered separately in our article about multifocal IOLs.

To determine whether ICL implantation is suitable for your eyes and which lens size would be appropriate, you should undergo a comprehensive examination, including corneal endothelial cell assessment, and consult an ophthalmologist.

Sources

[1] Barsam A, Allan BD. Excimer laser refractive surgery versus phakic intraocular lenses for the correction of moderate to high myopia. Cochrane Database of Systematic Reviews. 2014;6.

[2] Kamiya K, et al. Eight-Year Outcomes of Implantation of Posterior Chamber Phakic Intraocular Lens With a Central Port for Moderate to High Ametropia. Frontiers in Medicine. 2021;8:799078.

[3] Korea Disease Control and Prevention Agency (KDCA). National Health Information Portal: Refractive Errors (Myopia, Hyperopia, and Astigmatism).

[4] Shen Z, et al. Small Incision Lenticule Extraction (SMILE) versus Femtosecond Laser-Assisted In Situ Keratomileusis (FS-LASIK) for Myopia: A Systematic Review and Meta-Analysis. PLoS One. 2016;11(7).

This article provides general information based on a Cochrane systematic review, peer-reviewed scientific literature, and publicly available information from the Korea Disease Control and Prevention Agency. It does not recommend any specific lens product or surgical procedure. The most appropriate treatment for your eyes should be determined through a comprehensive examination and consultation with an ophthalmologist.