The femtosecond laser automates several of the incisional steps of cataract surgery. The pneumonic FLACS is a shorter way to say Femtosecond Laser Assisted Cataract Surgery.
The femtosecond laser can perform four functions during cataract surgery.
1. Corneal incision
2. Astigmatic correcting arcuate incisions
3. Opening the anterior capsule of the cataract
4. Liquification (emulsification) of the cataract
FLACS does not automate the entire procedure. Many steps of cataract surgery, including removal of the cataract material from the eye, and placement of the new lens, are still done by the surgeon. Complication rates are low with both standard phacoemulsification and FLACS. The literature on refractive precision and safety does not consistently favor either method.
The Four Functions of FLACS
1. Corneal Incision
It is necessary to make an incision in the eye for removal of the cataract material, and placement of the lens. This can be done using a laser, or manually with a blade. Manual cataract surgical blades make a microscopically smooth incision using an highly polished metal or diamond blade. The femtosecond laser creates the incision with many small laser spots.
2. Astigmatism Correcting Arcuate Incisions
The femtosecond laser can create arcuate shaped, non full-thickness incisions at the outer edge of the cornea to change the shape of the cornea. This can reduce refractive astigmatism postoperatively.
The femtosecond laser can potentially correct small amounts of astigmatism, below the levels treated by toric lenses. The levels of astigmatism that are best treated with the femtosecond laser are low enough that results cannot be guaranteed. If you have the correct corneal characteristics, opting for FLACS astigmatic management during cataract surgery may improve your chances of an ideal outcome, but does not guarantee it.
3. Opening the Anterior Capsule of the Cataract (capsulorhexis)
Think of cataract surgery as a system for building a camera. The artificial lens is placed inside the thin, clear, capsule that remains after the cataract has been removed. During surgery, the anterior portion of this capsule is opened in order to remove the cataract inside, and place the lens. When this is done manually, it is like drawing a circle by hand. The size, shape and centration of the circle might not be exactly the same every time. The femtosecond laser improves the precision of the shape, size, and location of the capsulorhexis.
The shape of a manual capsulorhexis cannot be as precise as a femtosecond laser capsulorhexis. However, an experienced surgeon can make a manual capsulorhexis that is very close. The difference between a femtosecond laser capsulorhexis and a manual one can be compared to the difference between a skilled artist drawing a circle by hand, and a machine-drawn perfect circle. In the months to years after surgery, the capsule will wrinkle, shrink and change a little bit. This perfection of the circle created by the femtosecond laser is not permanent.
In theory, a perfect capsulorhexis will facilitate the greatest consistency in the position of the intraocular lens within the eye in all three dimensions. Whether or not the femtosecond laser for capsulorhexis actually delivers a better optical result is still a subject of controversy.
4. Fragmentation and liquification of the natural lens
It is necessary to liquefy (emulsify) the solid lens material in order to remove the natural lens using today’s small incisions. The femtosecond laser softens the cataract material. With manual phacoemulsification cataract surgery, this is done using a probe that delivers ultrasound energy. In either case, the same ultrasound probe is used to actually remove (aspirate) the material.
The femtosecond laser can reduce the energy required to remove the cataract, which may help protect the inside of the cornea during surgery. The clinical significance of this is still being studied and debated.