Is ICL (Implantable Collamer Lens) Right for Everyone? Understanding the Eligibility Criteria

Essential Pre-operative Inspections and Considerations Shared by an Ophthalmologist

Q: "I was told my corneas are too thin for LASIK or LASEK. Is Implantable Collamer Lens (ICL) surgery an option for me?"

Hello. I am Dr. Yoon Jung Song, Ophthalmologist at BGN Eye Clinic Jamsil.

This is one of the most frequent questions I receive from patients with high myopia or those who have been told that laser vision correction is not viable due to thin corneas. While ICL is an excellent alternative that preserves the cornea without any laser cutting, it is not suitable for everyone. Today, based on strict clinical guidelines, I will explain in detail the eligibility criteria, cases where the surgery may not be recommended, and the essential features you must know before making a decision.

What is ICL (Implantable Collamer Lens) Surgery?

ICL is an advanced vision correction method that corrects vision without altering or shaving the cornea, making it an excellent alternative for those who cannot undergo LASIK or LASEK. The procedure involves inserting a specially designed biocompatible lens between the iris and the natural lens of the eye. It is highly recommended for individuals with thin corneas, severe nearsightedness (high myopia), or high astigmatism.

Am I a Candidate for ICL?

To determine if you are eligible for ICL, your eye’s anatomical structure must meet specific clinical parameters. You may be an ideal candidate if you meet the following conditions:

• High or Extreme Myopia: Patients with high myopia require a significant amount of corneal tissue removal for laser correction. If shaving the cornea poses a risk, ICL serves as a safer, non-destructive alternative.
• Thin or Irregular Corneas: Since LASIK and LASEK reshape the cornea using a laser, corneal thickness and shape are critical. If your residual corneal thickness is insufficient, ICL is recommended because it leaves your cornea completely intact.
• High Astigmatism: For individuals with astigmatism, a specialized 'Toric ICL lens' can be used to correct the astigmatic axis. A precise evaluation of your unique astigmatism axis and power will determine your eligibility.
• Sufficient Intraocular Space: This is the most critical physical requirement for ICL. There must be adequate room (Anterior Chamber Depth) for the lens to safely sit. Additionally, the corneal endothelial cell count, which maintains corneal clarity, must be within a safe, age-appropriate range. 

When is ICL Not Recommended?

Because this procedure involves placing a lens inside the eye, surgery may need to be postponed or alternative options explored if any of the following clinical findings are present during your examination:

• Insufficient Space for the Lens: If the anterior chamber depth is too shallow, there is physically not enough space to safely position the lens without risking contact with internal structures.
• Low Corneal Endothelial Cell Count: If your endothelial cell count or cell shape does not meet safety thresholds, placing an intraocular lens could compromise your long-term corneal health.
• Underlying Ocular Diseases: Active conditions such as cataracts, glaucoma, or macular/retinal diseases require treatment first, and may disqualify you from receiving ICL.
• Unstable Vision: If your prescription has changed within the last 6 to 12 months, your vision is not yet stable enough for a permanent implant.
• Hormonal Fluctuations: Pregnancy or breastfeeding can temporarily alter corneal curvature and refractive power, making it necessary to delay the procedure.

Key Features of ICL: Pros and Cons

Advantages

Since there is no corneal shaving, ICL carries a significantly lower risk of severe dry eye syndrome associated with corneal nerve damage. The natural structure of the cornea is fully preserved. Furthermore, the procedure is completely reversible; should any issues arise in the future, the lens can be safely removed or replaced by a specialist.

Precautions & Disadvantages

Due to the use of highly specialized biocompatible lenses and precise micro-surgical techniques, the cost of ICL is relatively higher than that of LASIK or LASEK. Some patients may also experience temporary glare or halos at night depending on their pupil size. While there is a minimal risk of increased intraocular pressure if the lens sizing is not perfect, modern lens designs with central holes (such as Aqua ICL) have dramatically improved fluid flow and minimized this risk.

"When consulting patients for ICL, the absolute first things we verify are whether there is sufficient physical space inside the eye to house the lens and if the corneal endothelial cells are healthy. Because everyone's ocular anatomy is unique, a thorough, highly precise examination is the most important step of all."

— Dr. Yoon Jung Song, BGN Eye Clinic Jamsil

Essential Diagnostic Tests for Personalized Vision Correction

ICL requires analyzing the internal structures of your eye down to the micrometer (㎛). A comprehensive pre-operative screening is vital:

• Refractive Error Test: To accurately measure the exact degree and axis of myopia, hyperopia, and astigmatism.
• Corneal Topography: A 3D analysis of the thickness and shape of both the front and back surfaces of the cornea.
• Corneal Endothelial Cell Exam: Checks the number and health of the cells responsible for keeping the cornea clear and transparent.
• Anterior Chamber Depth (ACD) Test: Measures the distance between the iris and the cornea to ensure there is enough room to safely insert the lens.
• Intraocular Pressure (IOP) Test: Assesses pre-operative eye pressure to rule out glaucoma risks.
• Fundus Examination: Evaluates the overall health of the back of the eye, including the retina and optic nerve.

Frequently Asked Questions (FAQ)