Thin-flap LASIK, also called sub-Bowman’s keratomileusis (SBK), involves creating a thinner flap than flaps traditionally produced in LASIK surgery.

A thinner flap may reduce the risk of dry eyes after LASIK. It also may preserve greater corneal strength, thereby reducing the risk of corneal ectasia after the procedure.

Using a microkeratome in thin-flap LASIK also may lower LASIK cost, as the equipment costs for these mechanical instruments are significantly less for LASIK surgeons than costs associated with femtosecond lasers.

Single-use microkeratome: Study design and methods

Dr. Tamayo conducted a study at Bogota Laser Refractive Institute (Bogota, Columbia) to compare the outcomes of 40 eyes undergoing thin-flap LASIK with corneal flaps created with the Moria One Use-Plus single-use microkeratome or a femtosecond laser.

In all cases, the intended flap thickness was 100 microns.

Prior to surgery, the mean amount of myopia in the microkeratome group was -1.50 D. In the femtosecond laser group, it was -2.25 D.

Flap thickness was measured with an ultrasonic device during surgery immediately after the flaps were created.

Single-use microkeratome: Study results

Analysis of data gathered in the study revealed:

• Mean flap thickness was very similar in the two groups: 101 microns in the microkeratome group (range: 85 to 108 microns) and 104 microns in the femtosecond laser group (range: 82 to 110 microns).
• Corneas in the microkeratome group showed slightly more decrease in biomechanical stability factors than corneas in the femtosecond laser group.

(Note: a 30-micron range is equivalent to 0.3 millimeter.)

Dr. Tamayo said other larger studies also have shown the microkeratome is capable of producing thin flaps with excellent reproducibility of flap dimensions.

In addition, these studies have demonstrated that thin flaps created with the Moria microkeratome are nearly planar (of equal thickness throughout) and the underlying corneal bed after flap creation with the microkeratome is smoother than the underlying corneal bed after flap creation with a 60-kHz femtosecond laser.

Single-use microkeratome: Conclusions

Dr. Tamayo concluded that the Moria One Use-Plus microkeratome with disposable, single-use components is safe, effective and reliable for creating flaps in thin-flap LASIK, and it provides excellent outcomes at a lower cost than femtosecond lasers.

SOURCE:  Single-use mechanical microkeratome offers reliable, safe, effective alternative for SBK. Ophthalmology Times. June 15, 2009.

Of the 500 surgeons on the Panel, 31 responded to the survey.

Among the results:

• 72 percent of the respondents say they have modified their surgical approach to reduce LASIK risks, especially the risk of ectasia — a rare but serious LASIK complication that can cause permanently reduced vision.
• Approaches respondents are using to reduce the risk of ectasia include: paying more attention to pre-existing optical aberrations of the eye when screening LASIK candidates; using a more conservative criterion for minimum residual corneal thickness under the LASIK flap after surgery; creating thinner LASIK flaps with a femtosecond laser to preserve corneal thickness under the flap.
• Regarding laser vision correction preferences, 55 percent of the respondents prefer wavefront-guided LASIK, 20 percent prefer conventional LASIK and 15 percent prefer PRK.
• 73 percent of the LASIK surgeries performed by the respondents are custom LASIK procedures.
• The average LASIK cost charged by the respondents is $2,273 per eye.

If an enhancement surgery is needed to improve visual outcomes of LASIK, 82 percent of the respondents say they prefer to lift the original LASIK flap and the rest say they prefer to perform a surface ablation procedure such as PRK.

SOURCE:  National Panel reflects on refractive surgery. Review of Ophthalmology. July 2009.

The surveys were conducted separately by the American Society of Cataract and Refractive Surgery (ASCRS) and the International Society of Refractive Surgery of the American Academy of Ophthalmology (ISRS/AAO).

Femtosecond laser use: ASCRS survey

In the recent (2008) ASCRS survey, 33 percent of the respondents said they prefer using an IntraLase femtosecond laser to a microkeratome for creating LASIK flaps. Another one percent said they prefer using a Ziemer Femto LDV femtosecond laser.

By comparison, the 2003 ASCRS survey found that only one percent of surgeons responding preferred performing all-laser LASIK with a femtosecond laser to create the corneal flap.

Femtosecond laser use: ISRS/AAO survey

In the 2008 ISRS/AAO survey, 40 percent of surgeons responding said they preferred using an IntraLase laser to a microkeratome. In 2003, only eight percent of respondents said they preferred using a femtosecond laser.

Reasons for increased use of femtosecond lasers

Experts say this trend toward greater use of femtosecond lasers in LASIK surgery is due in part to consumer demand for blade-free, all-laser LASIK.

In response to consumer demand for all-laser LASIK, LCA-Vision, owner of 75 LasikPlus Vision Centers in 34 states and 60 markets in the U.S., recently announced it will offer exclusively all-laser LASIK in its surgery centers.

Experts also cite a growing body of evidence that femtosecond lasers are more predictable than microkeratomes and may produce fewer negative outcomes, such as dry eye, after LASIK surgery.

Microkeratomes: Still preferred by many surgeons

Many surgeons, however, still prefer using a microkeratome to create LASIK flaps.

They point out that today’s modern microkeratomes are more predictable and can accurately cut thinner flaps than previous models. Flap creation also is quicker with a microkeratome, which may reduce patient anxiety during the procedure.

LASIK cost is another issue. Because microkeratomes are significantly less expensive than femtosecond lasers, surgeons can charge a lower fee for LASIK with a blade-cut flap.

More femtosecond laser choices for surgeons

Another indicator of the growing popularity of all-laser LASIK is the increased number of femtosecond lasers available to U.S. refractive surgeons.

For years, the only FDA-approved femtosecond lasers were made by IntraLase (now owned by Abbott Medical Optics). Today, alternative femtosecond lasers available to LASIK surgeons in the U.S. include the VisuMax (Carl Zeiss Meditec), the Femtec (Technolas) and the Femto LDV (Ziemer).

SOURCE:  Femtosecond laser use in US increasing, but some still prefer microkeratomes. Ocular Surgery News. June 2009.