LASIK, or Laser-Assisted In Situ Keratomileusis, is a procedure that corrects common vision problems by reshaping the cornea, the clear front surface of the eye. This vision correction surgery has undergone significant evolution since its introduction, moving away from mechanical instruments to highly precise laser systems. Modern LASIK is defined by sophisticated technology that enables customized treatment, enhancing both the safety and the quality of visual outcomes.
Femtosecond Laser Technology for Flap Creation
Modern LASIK procedures begin with the creation of a thin, hinged flap on the cornea’s surface, a step now performed almost universally with a femtosecond laser rather than a mechanical blade. This ultra-fast laser emits pulses of light in the infrared wavelength, delivered in trillionths of a second. These pulses focus precisely beneath the corneal surface to create microscopic bubbles of water and carbon dioxide, a process called photodisruption.
The bubbles are arranged in a specific pattern to define the flap’s edges and its plane of separation from the underlying corneal tissue. Surgeons can precisely control the flap’s diameter, hinge position, and thickness, which contributes to a more predictable procedure compared to older mechanical methods. This bladeless technique has become the standard for LASIK, improving patient safety and flap stability.
Advanced Mapping for Customized Ablation
The customization in modern LASIK comes from advanced diagnostic imaging that maps the unique imperfections of a patient’s eye beyond a standard prescription. After the corneal flap is lifted, an Excimer laser reshapes the underlying stroma according to this specific data. This process targets subtle irregularities, known as higher-order aberrations, that can affect the quality of vision, particularly in low light.
One method is Wavefront-Guided ablation, which measures how light travels through the entire optical system of the eye. This technique creates an intricate map of the visual pathway, identifying distortions that contribute to issues like glare or halos. The Excimer laser then uses this map to apply a unique treatment profile, aiming to optimize the overall optical performance of the eye.
A separate approach is Topography-Guided ablation, which focuses exclusively on mapping the surface curvature of the cornea itself. This system creates an elevation-based map of the cornea’s front surface, identifying minute irregularities. Topography-guided LASIK is often used to treat irregular astigmatism or to correct irregularities from previous eye surgeries or injuries. This method may be effective at reducing certain higher-order aberrations like coma and trefoil, leading to a high quality of vision.
Small Incision Lenticule Extraction (SMILE)
Small Incision Lenticule Extraction (SMILE) is an advancement in laser vision correction that moves beyond the traditional LASIK flap procedure. This minimally invasive technique uses only the femtosecond laser. SMILE is currently approved for the correction of nearsightedness and astigmatism.
The femtosecond laser first creates a small, lens-shaped piece of tissue, known as a lenticule, within the intact corneal layers. The laser then makes a tiny incision, typically less than four millimeters wide, through which the surgeon removes the lenticule. Removing this precisely shaped tissue changes the curvature of the cornea, thereby correcting the refractive error.
Because SMILE does not involve creating a large, hinged flap, it is associated with less disruption to the corneal surface nerves. This smaller incision may offer biomechanical advantages, potentially preserving more of the cornea’s natural strength and leading to a lower incidence of postoperative dry eye symptoms compared to traditional LASIK.