Introduction
Understanding the surgical procedure behind EVO ICL empowers patients to approach their experience with realistic expectations, reduce pre-operative anxiety, and recognize the technical decisions their surgeon is making on their behalf. EVO ICL implantation is a sophisticated intraocular surgical procedure. It is minimally invasive by the standards of eye surgery, but it is still surgery inside the eye — and the surgeon’s training, judgment, and technical skill directly influence the outcome.
The procedure itself takes 20 to 30 minutes per eye in the hands of an experienced surgeon. But that brief time in the operating room is the product of extensive pre-operative planning, precise measurements, and meticulous surgical execution. Every step has a clinical rationale, and every decision the surgeon makes during the procedure reflects both established technique and individual adaptation to the patient’s unique anatomy.
This guide walks through the procedure comprehensively — from the final pre-operative preparation to the first post-operative exam — so that patients know exactly what to expect and can distinguish between normal experiences and signals that warrant prompt follow-up.
For a directory of surgeons recognized for exceptional procedural skill and outcomes, visit the EVO ICL Awards hub.
Section 1: Pre-Operative Planning and Day-of Preparation
Lens Selection and Sizing
Before surgery is scheduled, the surgeon uses a set of biometric measurements to calculate the appropriate EVO ICL for each patient. The key measurements include:
- White-to-white (WTW) distance: The horizontal diameter of the cornea, measured from limbus to limbus. This is the primary input for determining which lens size to use.
- Anterior chamber depth (ACD): The space from the corneal endothelium to the anterior surface of the natural lens, used to confirm adequate room for the implant and to predict vault.
- Manifest and cycloplegic refraction: The patient’s prescription, used to select the appropriate optical power.
- Sulcus-to-sulcus (STS) distance: In practices using ultrasound biomicroscopy (UBM), the actual distance between the ciliary sulcus structures — the anatomical landmarks where the ICL haptics will rest — can be measured directly, allowing more precise sizing than WTW alone.
STAAR Surgical provides a sizing nomogram that surgeons use to translate these measurements into a lens size recommendation. Experienced surgeons may apply center-specific adjustments to the nomogram based on their outcomes data — a refinement that reflects accumulated clinical experience.
Pre-Operative Drops and Medications
On the day of surgery, patients typically instill a series of eye drops in the hours beforehand. These include:
- Dilating drops (mydriatics): To widen the pupil, improving the surgeon’s access to the posterior chamber for lens positioning.
- Non-steroidal anti-inflammatory drops: To reduce intraocular inflammation during and after the procedure.
- Topical antibiotic drops: To reduce the surface bacterial load before an intraocular procedure.
A mild oral sedative (such as diazepam) is sometimes offered for anxious patients, though many undergo the procedure without any systemic medication.
What Patients Should Arrange
Patients must arrange transportation home on the day of surgery — driving is not permitted due to the dilating drops and the effects of any sedative taken. Vision may be blurry from dilation for several hours following the procedure even if surgical visual acuity is already improving. Patients should plan to rest for the remainder of the day and avoid screens, reading, and physical exertion.
Section 2: The Surgical Procedure Step by Step
Anesthesia and Patient Positioning
EVO ICL surgery is performed under topical anesthesia — numbing eye drops are applied to the ocular surface, and no injections are required. The patient lies supine under an operating microscope. A lid speculum is placed to gently hold the eyelid open, eliminating the need for the patient to consciously avoid blinking.
Patients remain awake throughout the procedure. They may see lights and movements but should not experience pain. A small percentage of patients report mild pressure sensations, particularly during incision creation or lens positioning.
Incision Creation
The surgeon creates a small clear corneal incision, typically 2.5 to 3.0 millimeters in length. A second, smaller paracentesis incision (approximately 1.0 mm) is made approximately 90 degrees away from the primary incision to allow introduction of instruments for lens positioning.
The incision is placed at the limbus — the junction between the transparent cornea and the white sclera — or slightly into clear cornea, depending on surgeon preference and anatomical considerations. The placement affects the incision’s healing characteristics and its contribution to astigmatism (which for very small incisions is minimal).
Viscoelastic Injection
Before lens insertion, the surgeon injects a viscoelastic material — a thick, clear gel — into the anterior chamber. Viscoelastic serves two purposes: it creates space in the anterior chamber to safely maneuver the lens, and it coats the corneal endothelium to protect these non-regenerating cells from surgical trauma. After lens implantation, the viscoelastic is removed to prevent it from blocking aqueous drainage and raising intraocular pressure.
Lens Insertion and Positioning
The EVO ICL — which has been loaded into a specialized injector cartridge — is introduced through the primary incision and injected into the anterior chamber. The lens unfolds gradually as it enters the eye. The surgeon uses a fine instrument introduced through the paracentesis to guide the lens haptics (the flexible arms at each end of the lens) behind the iris and into the ciliary sulcus.
Positioning all four haptics correctly behind the iris, with the optic centered on the pupil, requires precision and confidence. An experienced surgeon performs this portion of the procedure efficiently and smoothly. Prolonged manipulation increases surgical trauma and the risk of transient corneal edema.
For toric ICL implantation, the surgeon must also align the lens to the correct rotational axis to ensure that the cylinder correction is oriented precisely. Toric axis alignment is typically marked on the eye pre-operatively using the slit-lamp with the patient in an upright position, since the eye can rotate slightly when the patient lies supine on the operating table.
Viscoelastic Removal
Once the lens is positioned correctly, the surgeon uses an irrigation and aspiration handpiece to remove the viscoelastic from the anterior chamber, including viscoelastic that may have passed behind the lens. Thorough viscoelastic removal is essential — retained viscoelastic can block the trabecular meshwork and cause a post-operative intraocular pressure spike.
Incision Hydration and Wound Check
The self-sealing incision is tested for watertight integrity by applying gentle pressure adjacent to the wound and observing for fluid egress. If the wound does not seal adequately with hydration alone, a suture may be placed — though this is uncommon with properly constructed micro-incisions.
Section 3: How Expert Surgeons Approach the Procedure
Efficiency and Tissue Preservation
Surgical time and the number of instrument passes inside the eye are directly correlated with intraocular trauma and post-operative inflammation. Surgeons who have performed hundreds of EVO ICL implantations develop an efficiency of movement that minimizes unnecessary manipulation. They position the lens haptics in one or two deliberate steps rather than repeated probing.
The EVO ICL Awards program evaluates surgeons in part by their complication rates and outcomes consistency, which are indirect markers of surgical technique and efficiency.
Intraoperative OCT and Advanced Visualization
Some high-volume EVO ICL practices use intraoperative OCT (optical coherence tomography) to confirm vault in real time on the surgical table before concluding the procedure. This technology allows immediate assessment of lens position and early identification of sizing concerns while the patient is still in the operating room — a capability that represents the leading edge of procedural refinement.
Managing Unexpected Findings
Even with thorough pre-operative evaluation, surgeons occasionally encounter unexpected anatomical findings during surgery — an unusual iris configuration, a slightly shallow sulcus, or an unanticipated degree of lens unfolding. Expert surgeons adapt their technique in real time. They also know when to stop and reschedule rather than proceed under suboptimal conditions — a judgment that prioritizes patient safety over surgical completion.
Section 4: What Patients Should Look For in a Surgical Practice
When evaluating where to have EVO ICL surgery, patients should investigate the following:
Surgical setting and sterility standards. EVO ICL is an intraocular procedure performed in an accredited ambulatory surgical center or a hospital operating room, not an office procedure room. Confirm that the facility meets appropriate sterility and safety standards.
Surgeon volume. Ask the surgeon how many EVO ICL procedures they have performed in total and how many per year. While no universal minimum exists, surgeons with higher cumulative volume have more experience with the range of anatomical variations and intraoperative challenges they may encounter.
Lens inventory and injector systems. Ask whether the practice uses the current generation of STAAR Surgical’s EVO ICL and the compatible injector system. Older lens designs or improvised injection techniques can increase the risk of surgical complications.
Post-operative monitoring capability. The practice should have the equipment and protocol to measure intraocular pressure and assess vault on the morning after surgery. An IOP spike that is not identified and treated promptly can cause visual damage. See EVO ICL Recovery: What to Expect After Surgery for what the post-operative period entails.
For guidance on evaluating surgeon credentials more broadly, see EVO ICL Surgeon Credentials: What to Look For.
Frequently Asked Questions
Is EVO ICL surgery painful? The procedure is performed under topical anesthesia and is not painful for the majority of patients. Mild pressure sensations during lens positioning are possible. Some patients experience transient discomfort from the lid speculum. Post-operatively, mild scratchiness and light sensitivity are common and typically resolve within 24 to 48 hours.
Can both eyes be treated on the same day? Many surgeons and patients prefer to treat both eyes on the same day for convenience. Some surgeons prefer to perform one eye, confirm the outcome at the next-day visit, and then proceed with the second eye. Discuss this with your surgeon. See EVO ICL Recovery: What to Expect After Surgery for timing considerations.
What happens if the lens is the wrong size? If vault is significantly outside the target range (too low or too high), the surgeon may recommend lens exchange — removing the original ICL and replacing it with a different size. This situation is uncommon with accurate pre-operative measurements but can occur. Experienced surgeons have lower lens exchange rates. See EVO ICL Safety Profile and Clinical Results for context.
How long does the EVO ICL remain effective? The lens is designed to remain in the eye indefinitely. Long-term clinical data from markets where ICL has been used for more than 20 years shows that the lens maintains its optical clarity and position over time. The only anticipated reason for removal is future cataract surgery or a significant prescription change requiring lens exchange.
Next Steps
Having a clear understanding of what happens during EVO ICL surgery helps you evaluate your surgeon’s expertise, ask informed questions, and approach the procedure with confidence rather than anxiety. The technical quality of the surgery itself is one of the most important determinants of your outcome.
Visit the EVO ICL Awards hub to find surgeons recognized for procedural excellence and consistently strong patient outcomes in your area.