What is ICL (Implantable Collamer Lens)? Safety and Side Effects Explained by an Ophthalmologist 

Objective facts about corneal-preserving vision correction, operating principles, and safety factors.

Q. "I was recommended ICL surgery, but the thought of placing a lens inside my eye makes me worry about safety and side effects."

Hello, I am Dr. Yoon-Joong Song from BGN Eye Clinic Jamsil.

Meeting patients in the examination and consultation rooms, one of the most common questions I receive is regarding the safety and potential side effects of Implantable Collamer Lens (ICL) surgery. Concerns such as "Could the lens move around inside my eye?" or "Can it be reversed if a problem occurs later?" often stem from vague anxiety. Today, I would like to clarify the facts behind these common fears.

What Exactly is ICL (Implantable Collamer Lens) Surgery?

ICL surgery is a procedure that corrects vision by inserting a specially crafted micro-lens behind the iris (in front of the natural crystalline lens) without cutting or reshaping the cornea. It is widely known by its medical abbreviation, ICL (Implantable Collamer Lens).

Since laser vision correction methods like LASIK or LASEK reshape and remove a specific amount of corneal tissue, they may have limitations for individuals with extreme high myopia, thin corneas relative to their prescription, or severe astigmatism. In contrast, ICL surgery preserves the natural corneal structure intact, making it a viable alternative when considering vision improvement without the burden of corneal thickness constraints.

Common Misconceptions and Side Effects of ICL

Many patients hesitate due to unverified online information or vague fears about ICL risks. Here are the objective facts regarding the most frequent misconceptions and side effects encountered in clinical practice.

Misconception 1. Will the inserted lens move out of place inside the eye?

To give you a direct answer, a custom-sized lens designed to your exact eye dimensions cannot move around freely. The lens is safely positioned in the stable "posterior chamber" between the iris and the natural lens. As long as appropriate lens sizing and positioning are secured, the likelihood of dislocation is extremely low. For patients with astigmatism, Toric ICLs are designed to minimize rotation and are meticulously aligned along the precise astigmatic axis.

Misconception 2. Is the procedure irreversible once completed?

It is actually the exact opposite. One of the greatest advantages of ICL surgery is its reversibility. Unlike laser procedures that permanently remove corneal tissue, ICL allows the lens to be removed or replaced if unexpected changes or ocular diseases develop later, restoring the eye to its pre-surgery state.

Misconception 3. Does it severely worsen dry eyes and increase intraocular pressure (IOP)?

This concern originates from early-generation lens models. Because ICL surgery does not disrupt or cut the surface nerves of the cornea, the risk of postoperative dry eye syndrome is significantly lower compared to laser methods.

Furthermore, modern EVO+ ICL lenses feature a central hole design that facilitates natural aqueous humor circulation inside the eye. This structural innovation minimizes the risk of elevated intraocular pressure and related complications.

Is There Enough Space in My Eye? (Precision Measurement & Q&A)

Q. "How can I check before surgery if there is sufficient space in my eye for the lens?"

A. One of the most critical factors we evaluate in the consultation room is the physical space inside the eye. During preoperative examinations, we rigorously measure whether the Anterior Chamber Depth (ACD) meets the safe threshold (typically 2.8mm or greater) and confirm that the corneal endothelial cell density, which maintains corneal clarity, falls within a safe range. Only when these criteria are fully met do we proceed to customized lens design. 

At BGN Eye Clinic Jamsil, we utilize a multi-dimensional diagnostic system including UBM (Ultrasound Biomicroscopy) to provide tailored solutions ranging from internal ocular structure analysis to astigmatism axis calculations. Because ICL surgery does not reshape the corneal stroma, recovery is remarkably fast, most patients can comfortably resume light daily activities the day after surgery, provided there are no unusual clinical findings.

Rather than delaying your decision due to vague concerns, we recommend scheduling a comprehensive examination to accurately understand your eye condition.