The goal of LASIK (Laser-Assisted In Situ Keratomileusis) is to correct refractive errors like nearsightedness, farsightedness, and astigmatism by precisely reshaping the cornea. To access the underlying corneal tissue, called the stroma, the procedure first requires creating a thin, hinged flap on the cornea’s surface. This flap is lifted, the stroma is reshaped using an excimer laser, and the flap is then repositioned for natural healing. The method used to create this initial flap is the primary difference between traditional and bladeless LASIK.
Traditional LASIK: The Microkeratome Flap
Traditional LASIK utilizes a mechanical instrument known as a microkeratome to create the corneal flap. This device is a precise surgical tool that incorporates a metal blade. The microkeratome is secured to the eye using a suction ring, which immobilizes the tissue and slightly raises the intraocular pressure.
Once secured, the device’s oscillating blade moves across the cornea to make a uniform cut, creating a flap that remains attached by a small hinge of tissue. This method has been used successfully for decades and was the original standard procedure for LASIK. The entire flap creation process is quick, often taking less than 30 seconds.
Bladeless LASIK: Femtosecond Laser Technology
The modern approach, often called bladeless or all-laser LASIK, replaces the mechanical blade with a femtosecond laser. This technology employs ultra-fast pulses of infrared light, each lasting only a quadrillionth of a second (a femtosecond), to separate the corneal tissue. The laser focuses its energy at a pre-programmed depth within the cornea, causing photodisruption.
Photodisruption vaporizes a microscopic amount of tissue, creating tiny, interconnected bubbles of gas and water vapor. By firing thousands of these pulses in a specific pattern, the surgeon traces the outline and depth of the flap from the inside out. This bubble layer creates a smooth plane of separation, allowing the surgeon to lift the flap without using a physical blade. The ability to program the flap’s dimensions and shape is a distinction of this laser-based method.
Surgical Precision and Flap Integrity
The difference in cutting mechanisms leads to variations in the quality and predictability of the resulting corneal flap. The mechanical microkeratome, while precise, is subject to inherent variability, often resulting in a flap with non-uniform thickness. Studies show that the thickness of microkeratome-created flaps can vary by a greater range than intended.
In contrast, the femtosecond laser offers the surgeon greater control and customization over the flap’s architecture. The laser allows for programming the exact thickness, diameter, and the angle of the side-cut (the vertical edge of the flap). This results in a flap that is more uniform in thickness and creates a steeper, more vertical edge compared to the flatter angle created by a blade. This vertical side-cut angle contributes to a better seal when the flap is repositioned, aiding in faster healing and increasing the flap’s resistance to displacement.
Differential Complication Rates
While both methods are considered safe, the nature of potential complications relates directly to the flap creation technology used. Traditional LASIK with a microkeratome carries unique risks associated with the physical cutting action. These include incomplete or irregular flaps (where the cut stops prematurely), a “buttonhole” flap (where the blade cuts through the center), or, in rare cases, a “free cap” (where the flap is completely detached from the hinge).
The bladeless approach eliminates mechanical cutting errors but introduces complications specific to the laser’s photodisruption process. One complication is the opaque bubble layer (OBL), a collection of gas bubbles trapped within the corneal tissue that can interfere with the subsequent excimer laser treatment. Another temporary complication is Transient Light Sensitivity Syndrome (TLSS), an inflammatory response causing severe light sensitivity for a short period after the procedure. Overall, flap-related complications are less frequent and less severe with the femtosecond laser.
Deciding the Best Approach
The choice between traditional and bladeless LASIK is influenced by medical necessity, surgeon preference, and cost. The precision of the femtosecond laser has expanded candidacy for LASIK, allowing patients with thin corneas or unusual corneal shapes to be treated safely. For these individuals, the laser method may be the only viable option.
However, the complexity of the femtosecond laser system makes bladeless LASIK more expensive than the microkeratome-based procedure. Patients must weigh the cost difference against the benefits of increased flap predictability and the reduction of mechanical flap-related risks. The most important step remains a consultation with a refractive surgeon who can recommend the approach best suited to the individual’s ocular anatomy.