Mechanical Microkeratomes vs Femtosecond Lasers (LASIK Flap Creation)

Both mechanical microkeratomes and femtosecond lasers have their own advantages and disadvantages. Refractive surgery people continue to debate the benefits of these technologies over one another.

In this article, we have briefed the pros and cons of both mechanical microkeratomes and femtosecond lasers for the LASIK flap creation

Being a modern technology, femtosecond lasers have revolutionized the process of lamellar flap creation. They have superior predictability and accuracy. However, microkeratomes enjoy a competitive edge due to their affordability and versatility.

Microkeratomes also have evolved and advanced technologically over the years. Market scope data indicates LASIK procedures (more than 65%) are still done using microkeratomes.

In spite of the higher costs, the femtosecond laser devices’ market share will continue to increase, according to various random studies. The manufacturing companies sell about 1,000 femtosecond laser systems every year.

Mechanical Microkeratomes and Femtosecond Lasers

Mechanical Microkeratomes

In mechanical microkeratomes, high or ultra-precision oscillating-blade arrangements anchor to suction rings. Holding the cornea under high pressure, this system creates a lamellar corneal flap. These devices have a proven track record and safety record for LASIK flap creation.

Various companies use different kinds of hinges on these devices. For example, pivoting systems make superior hinges and Translational microkeratomes make nasal hinges.

Similarly, Disposable systems produce single-use microkeratome heads. In some models, this company uses single-use suction rings also.

Femtosecond Lasers

A femtosecond (FS) laser is a near-Infrared laser. It has a wavelength of about 1.053 microns. Typically, it has a femtosecond range of pulse durations.

In cataract surgeries, a femtosecond laser mechanism emits multiple bursts of laser lights rapidly. This separates the tissues at molecular levels (micro activation) in the cornea, at specific depths.

Typically, each burst produces a bubble, that leaves about 2 – 3 cubic µm of cavitation volume. Across the cornea, thousands of bubbles are created in a raster pattern. This defines the interface medium between the stromal bed and flap.

After that, the bubbles are stacked starting from the interface edge to the epithelium. This completes the creation of flaps.

Benefits of Mechanical Microkeratomes

Mechanical microkeratomes have some advantages of their own including:

1.) Proven Records and Cost Competitiveness of Microkeratomes

In fact, Jose Barraquer and Cesar Carlos Carriazo invented microkeratome technology in the 1950s at Columbia. FDA approved IntraLase (laser flap maker) in 1999. Since then, surgeons have performed thousands of surgeries with this technology.

Right from inception, the complication rates were very less. Implementation of modern techniques further lowered the complication rates. Moreover, this system is a lot cheaper compared to femtosecond lasers. Hence, the patients can benefit from low surgical costs.

2.) Efficient Surgical Flow in Microkeratomes

Typically, the microkeratomes can create flaps in less than 30 seconds, from suction-on time to suction-off time. This is done without moving the bed of the patient, just before the excimer ablation.

On the other hand, the IntraLase system (4th Gen. 60 kHz) takes about 30 – 45 seconds of the time of suction-on, to create the flap. However, the laser operation to create a flap requires only about 15 -20 seconds.

In some excimer designs, it is not possible to use the same surgical bed for both flap creation (femtosecond laser) and excimer ablation. Therefore, the medical team has to shift the patients to different rooms or beds for each process.

3.) Easy to Create Flaps with Anterior Stromal Scar/ Opacity in Microkeratomes

In microkeratomes, mechanical systems are deployed to make cuts through the opacities. Hence, the process is easy, fast, and less complicated.

On the other hand, Femtosecond lasers can cause vertical gas breakthroughs during flap creation. This is especially true when an incisional surgery is performed before or the cornea has anterior stromal opacities.

4.) Lesser Discomfort and Inflammation

In modern microkeratomes, the advanced LASIK technology lowers the risk of sterile inflammations such as Diffuse lamellar keratitis (DLK) in the cornea. Technically, it is right to say, the occurrence of these types of problems is very rare in modern microkeratomes.

The instance of DLK was higher in Early generation femtosecond lasers. However, the modern IntraLase system (60khz) has significantly reduced the occurrence of OBL, TLS, and DLK issues

5.) Automatic Epithelial Flap Creations Using Microkeratomes

In microkeratomes, it is possible to set auxiliary equipment such as epi-LASIK for creating epithelial flaps automatically. Some microkeratome models come with prefixed auxiliary equipment also.

Femtosecond laser systems do have alternative options. It is up to the patients and their doctors to decide which procedure to go, based on cost and medical conditions.

Benefits of Femtosecond Laser h2

Femtosecond Laser systems have many advantages including:

1.) Lesser Complications Related to Flaps

In femtosecond laser systems, mechanical blades are not used. Moreover, they are fully guided by computers and related software in the modern world. Therefore, the possibility of flap-related complications is almost nil.

On the other hand, mechanical systems use physical blades. So, the chances of flap-related problems are comparatively high. These blades may malfunction or even stop working during the surgery due to various reasons.

However, modern technologies have helped to reduce such occurrences to significantly lower levels.

2.) Flexible Hinge Positions

In femtosecond laser systems, the doctors can change the hinge locations through the software interface. Examples of hinge positions include temporal, superior, nasal. Typically, this flexibility is beneficial while treating different conditions.

However, mechanical microkeratomes do not offer this flexibility. The surgeons have to switch to different systems.

3.) Fewer chances of Epithelial Ingrowth in Femtosecond laser systems

Generally, the chances of epithelial ingrowth are lower, when a femtosecond laser system is used to create flaps. The surgeons can precisely program the side cut angle, up to 90 degrees. This helps to lower the risks of epithelial ingrowth.

Comparatively, the chances of epithelial ingrowth are higher when microkeratomes are used to create flaps. These mechanical systems do not provide precise fine-tuning facilities.

4.) Precision Control on Hinge Width and Flap Diameter

Generally, the hinge widths and flap diameters are smaller on large, flat corneas and larger on narrow, steep corneas.

In femtosecond laser systems, the surgeons can precisely control both hinge width and flap diameter. Hence, they can easily work on different refractive errors and on different corneal sizes.

In addition, femtosecond laser systems have safety advantages, especially for more central, smaller flaps.

Mechanical microkeratomes do offer adjustable parameters for altering flap diameters. However, surgeons cannot precisely control the hinge width and flap diameter variabilities.

5.) Other Advantages of Femtosecond Laser Systems

In modern days, patients prefer femtosecond lasers over mechanical systems. In addition to those mentioned above, Femtosecond lasers have many other advantages. Some of those benefits include:

1.) The anxiety associated with the clinical procedure is comparatively less.

2.) Lesser higher-order aberrations compared to mechanical systems

3.) Improves quality of vision

Various randomized studies have confirmed these facts.

Conclusion

Being a modern, advanced technology, femtosecond laser systems have many advantages in various clinical situations. The flaps created using this technology result in more predictable, more consistent, and smaller changes in the biomechanics of the cornea.

However, mechanical microkeratomes have their own advantages. They incur less cost and have a proven track record of success. Depending on the cases and cost involved, the patients can discuss with doctors and select a suitable procedural method.

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