KLEx laser vision correction: CLEAR, SMILE, SMILE Pro, SmartSight and SILK

CLEAR, SMILE, SMILE Pro, SmartSight and SILK are advanced laser vision correction technologies that belong to a group of procedures known as keratorefractive lenticule extraction, or KLEx.
Although they are marketed under different names and performed using systems from different manufacturers, they all use a femtosecond laser. The main differences lie in the specific system used, its software and the features designed to assist the surgeon during the procedure.

All KLEx procedures work in the same way: the femtosecond laser creates a three-dimensional microlens (lenticule) within the intact cornea. Its thickness is precisely tailored to the refractive error being corrected. The surgeon then removes the lenticule through a very small opening, typically measuring just 2–4 mm. This changes the shape of the cornea, effectively correcting the refractive error.

CLEAR (Corneal Lenticule Extraction for Advanced Refractive Correction)

The CLEAR procedure is performed using the FEMTO LDV Z8 NEO femtosecond laser by Ziemer. The laser creates a lenticule within the cornea, together with a small peripheral opening measuring 2–4 mm.

• The technology uses ultra-low-energy, high-frequency pulses that overlap, allowing the corneal tissue to be separated with exceptional precision.
• The system enables precise centration of the laser pulses once the eye has been stabilised.
• A specially programmed tunnel created within the cornea helps the surgeon locate and gently separate the microlens before removing it through the small opening.

SMILE or SMILE Pro (Small Incision Lenticule Extraction)

In the SMILE and SMILE Pro procedures, a Carl Zeiss VisuMax femtosecond laser creates a lenticule within the cornea, together with a small opening. Through this opening, the surgeon separates the lenticule from the surrounding layers of the cornea and removes it. Removing this small amount of tissue changes the shape of the cornea, correcting the refractive error.

• Both SMILE and SMILE Pro use the same technology and systems from the same manufacturer. However, SMILE Pro is performed using a newer, faster laser platform (VisuMax 800)
• At some clinics, this procedure may be offered under a proprietary brand name, such as Lentivu®.

SmartSight

In the SmartSight procedure, the dedicated Schwind ATOS femtosecond laser creates a lenticule within the cornea, together with a small opening.

• The system provides advanced centration assistance, aligning the femtosecond laser treatment with the pupil, and compensates for potential eye rotation when the patient is lying down.
• The surgeon gently separates the lenticule from the surrounding corneal tissue and removes it through the small opening. This reshapes the cornea as planned, correcting the refractive error.

SILK (Smooth Incision Lenticule Keratomileusis)

The ELITA femtosecond laser by Johnson & Johnson creates a lenticule and a precise small opening within the cornea. Through this opening, the surgeon accesses the lenticule, which has a unique biconvex shape, gently separates it from the surrounding tissue and removes it. The remaining corneal tissue then naturally settles into its new shape, providing lasting correction of the refractive error.

What is the difference between CLEAR and SMILE procedures?

Summary – what does this mean for the patient?

For patients, CLEAR, SMILE, SMILE Pro, SmartSight and SILK are, in practical terms, the same type of safe procedure: a femtosecond laser creates a small lenticule within the cornea, which the surgeon then removes through a tiny incision. None of these procedures involves creating a corneal flap, as is the case with older techniques such as LASIK or FemtoLASIK. This significantly speeds up healing and reduces the risk of complications.

The main difference is that these are proprietary procedure names associated with specific medical devices. Each manufacturer has introduced its own technological enhancements, including different centration systems, advanced incision algorithms and sophisticated eye-tracking systems that monitor the patient’s eye movements.

Regardless of the technology used, the key to a successful outcome is always a thorough and accurate eligibility assessment, an individual evaluation of the eyes, consideration of the patient’s needs, and the experience of the surgeon, who must have an in-depth understanding of the capabilities of the equipment used at the clinic.

Frequently Asked Questions

1. Are KLEx procedures (CLEAR, SMILE, SMILE Pro, SmartSight and SILK) painful? 
No, these procedures are completely painless. Before the procedure begins, anaesthetic eye drops are administered to prevent any pain. During the laser treatment, which takes just a few seconds, patients may only feel slight pressure on the eye. After the procedure, once the anaesthetic wears off, some patients may experience temporary watering or a gritty sensation in the eyes, but these symptoms usually subside quickly.

2. How long does recovery take after a CLEAR, SMILE, SMILE Pro, SmartSight or SILK procedure? 
Recovery is extremely quick, allowing patients to return to their normal daily activities in a very short time. As the surgeon does not create a corneal flap and the incision is only 2–4 mm, the cornea heals very quickly. Most patients notice a significant improvement in visual acuity as early as the day after the procedure and can usually return to office work or driving at that point. Vision typically stabilises fully within a few weeks.

3. Who is a good candidate for KLEx laser vision correction?
These procedures are primarily used to correct myopia and astigmatism. They are an excellent option for people with active lifestyles, those who take part in contact sports, or those who work in demanding environments (e.g. members of the uniformed services), as the absence of a corneal flap eliminates the risk of flap displacement. The final decision on a patient’s eligibility for the procedure is always made by a doctor following a detailed examination of the cornea and an assessment of the tear film. 

4. How does KLEx laser vision correction differ from LASIK?
The main difference lies in how much the structure of the cornea is disrupted. In LASIK (or FemtoLASIK), the surgeon creates a circular corneal flap with a circumference of approximately 20 mm, lifts it, reshapes the underlying corneal tissue and then repositions the flap. With procedures such as SMILE or CLEAR, the laser works within the cornea without creating a flap on its surface, and the resulting lenticule is removed through a tiny incision (2–4 mm). This results in a lower risk of dry eye symptoms and faster healing. 

Back