Advances in femtosecond laser assisted cataract surgery (FLACS) providing better results, fewer complications, and higher rates of patient satisfaction.
Anaheim, CA-Advances in femtosecond laser assisted cataract surgery (FLACS) providing better results, fewer complications, and higher rates of patient satisfaction.
Kristin Symon, OD, says that optometrists can put them to work in their own practices.
She spoke at the American Academy of Optometry’s annual meeting in Anaheim, CA.
The mechanism of action behind femtosecond cataract surgery involves photodisruption of the corneal flap via high-powered laser. The rapid expansion and collapsing that occurs during photodisruption creates a separation of tissue, allowing surgeons to create incisions in the optic tissue.
“Femtosecond lasers have been used in the U.S. for corneal flap creation in LASIK since 2001,” says Dr. Symon. “And now we’re using the same femtosecond laser technology in new applications.”
FLACS received FDA approval in 2010.
The femtosecond laser offers several key advantages when applied to cataract surgery.
The wavelength of light emitted by the laser at low-intensity power is not absorbed by optically-clear tissues-like the cornea.
Says Dr. Symon: “The laser pulse can safely travel through the cornea to the target tissues-in this case, the lens.”
The femtosecond laser pulse is also unaffected by corneal magnification. She says this fact allows the laser to travel directly to the target without diversion due to corneal curvature.
Laser energy is easier to manage with this laser.
“This rapid pulse time for the laser allows for very small amounts of energy to be used while still delivering enough power for the application of laser to the desired tissue sparing delicate surrounding tissues,” Dr. Symon says.
Given its advanced nature, practitioners using FLACS will need to take several additional optic measurements during the pre-operative planning stages.
Aside from the usual cataract surgery measurements, including refraction, topography, and OCT scans, FLACS requires:
• Imaging of scleral vessels
• Calculations for optimal incision area and depth
• If astigmatism correction is needed, calculations of limbic relaxing incisions (LRI)
Each of these measurements is a necessary part of developing a pre-operative plan to help inform patients about the surgical process, she says.
As optometrists know, this type of pre-operative planning and consultation is essential for managing patient expectations and reaching higher levels of post-operative satisfaction.
Docking involves using a patient interface to help the laser recognize and align with the patient’s eye.
In LASIK patients, the docking process has been shown to cause a temporary spike in IOP.
While this isn’t always a problem, it is a concern during cataract surgery.
“In your cataract patients where concerns of glaucoma or vascular disease are more prevalent, this elevation in IOP can be more concerning,” Dr. Symon says.
Fortunately, in development are docking interfaces that reduce the IOP spike.
Physical limitations to the docking systems remain, and they are similar to those found in LASIK:
• Proper eye fixation is necessary for stable docking
• Patients must be able to lie flat
• Deep-set eyes or narrow palpebral apertures may prevent fitting of docking systems
Along with upgrades to the docking process, systems used for corneal imaging are seeing remarkable advancements as well.
Dr. Symon lists several ways new imaging technologies are improving corneal imaging:
• More precise corneal incisions
• Better location of scleral vessels
• Better placement of capsulotomy
• Fewer complications associated with intraoperative rupture of capsule
There are four primary surgical applications of the femtosecond laser procedure:
1. Corneal wound construction
2. Limbal Relaxing Incisions
3. Anterior capsulotomy
4. Lens fragmentation
“The clear corneal incision can have a very precise depth and shape when using the femtosecond laser,” says Dr. Symon.
Better visualizations of the clear corneal incision help reduce the risks of incisions that are too deep, which often result in:
• Wound leakage
• Iris prolapse
“Imprecise clear corneal incisions can induce astigmatism and create poor healing,” she says.
Manual incisions are less precise than the incisions made by the femtosecond laser.
LRIs correct up to 1.50 D of astigmatism and offers surgeons an alternative to toric intraocular implants (IOLs) for patients with low degrees of astigmatism.
“Overall, LRIs with the femtosecond laser are more precise and easier to achieve,” Dr. Symon says.
Capsulorhexis, a form of capsulotomy, is a technique used to remove the lens capsule during cataract surgery via shear and stretch forces.
FLACS provides more precise measurements for the surgical capsulotomy; too large, too small, or asymmetric capsulotomy all create optic problems.
Dr. Symon says that precision is key for this process. Precise centration, location, and size all impact patient outcomes.
“If the capsulotomy overall is too large, the IOL may tilt or rotate, becoming decentered, most commonly leading to a myopic shift in prescription overall.” she says. “If the capsulotomy is too small, it can develop fibrosis which can lead to a hyperopic shift in refraction. Manual capsulorhexis is considered one of the most difficult parts of cataract surgery.”
FLACS provides reduction of complications when compared to manual capsulorhexis, including:
• Decreased rate of tears in anterior capsule (0.18 percent vs. 1 percent)
• Decreased decentration of IOL (6x)
Femtosecond lasers are easier than traditional phacoemulsification on sensitive eye tissues.
In animal studies, ultrasound energy used during phaco has been shown to be a contributor to endothelial cell damage by creating oxidative stress that emits free radicals, according to Dr. Symon.
In femtosecond lens fragmentation, this ultrasonic energy was reduced by 39 percent.
“Complications in cataract surgery most frequently occur during phacoemulsification or due to phaco itself,” says Dr. Symon. “Therefore, anything that can reduce the phaco time and energy could theoretically make the procedure safer overall.”
Due to the benefits of FLACS, Dr. Symon says ideal candidates are:
• Those with dense cataracts
• Those needing refractive cataract surgery
• Those who require premium IOLs
• Those with Fuch’s corneal dystrophy
• Subluxation cases
However, she cautions that the procedure is not ideal for:
• Patients with poor dilation (often seen with Flomax [tamsulosin, Boehringer Ingelheim] use for enlarged prostate)
• Advanced glaucoma patients
• Nystagmus cases
• Those with dense corneal scarring
“At about a month postop, 82 percent of patients had less than 0.50 D difference from their target manifest refraction spherical equivalent,” Dr. Symon says.
Some 78 percent of patients in this same group had uncorrected visual acuities of 20/25 or better after FLACS treatments, she says.
Overall, patient satisfaction with FLACS was high, according to Dr. Symon. FLACS has the potential to improve pre-operative cataract surgery planning, increase surgical precision, and decrease the risk of complications in patients.